ML16314A994

Resumes

ML16314A994
Person / Time
Site:	Diablo Canyon
Issue date:	11/09/2016
From:	Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML16314A994 (202)

Text

'TTACHMENTS A. 'Resume - Richard B. Hubbard.

B. Biography - Eli Silver.

C. Biography - Clarence A. Hall, ~ Jr.

D. Resume - Stephan Alan Graham.

E'. Curriculum Vitae William R. Dickinson.

"The San Gregorio-Hosgri Fault Zone: An Overview," -'li Silver.

G. "Evidence for 115 Kilometers of Right Slip on the San 'Gregorio-Hosgri Fault Trend," S.A. Graham and W. R. Dickinson.

H. "San Simeon-Hosgri Fault System, Coastal California: Economic and Environmental implications," C.A. Hall, .Jr.

"Origin and Development of the Lompoc-S'anta Maria Pull-Apart Basin and its Relation to the 'San Simeon-Hosgri Strike-Slip Fault, Western California," C.A. Hall, Jr.

"Marine Geology and Tectonic History of the Central California Continental Margin," E.A. Silver, D.S. McCulloch, and J .R. Curry.

K. "Application of Linear Statistical Models of Earthquake Magnitude Versus Fault Length in Estimating Maximum Expectable Earthquakes,"

Robert K. Mark.

L. USGS Open File Report 77-614, "Regression Analysis of Earthquake Magnitude and Surface Fault Length Using the 1970 Data of Bonilla and Buchanan," R.K. Mark and M.G. Bonilla.

M. Biography - James N. Brune.

N. Curriculum Vitae - J. Enrique Luco, O. Curriculum Vitae - Mihailo D. Trifunac.

P. "Review of the 'Seismic Evaluation for Postulated 7.5M Hosgri Earthquake, Units 1 and 2, Diablo Canyon Site,'" J. Enrique Luco.

"Comments on Seismic Design Levels for Diablo Canyon Site in California," M. D. Trifunac.

R. USGS Open File Report 78-509, "Estimation of Ground Motion Parameters," D. M. Boore, A.A. Oliver, R.A. Page, and W.B. Joyner.

I T

gJ.

q d

q ATTACHE Z A l~hq- ~~

Richard B. Hubbard 366 California Avenue Suite 7 Palo Alto, CA 94306 (415) 329-0474 EXPERIENCE 9/76 - Present Partner - MHB Technical Associates, Palo Alto, California.'ounder an managing partner o tec nica consu ting irm. Specialists, in

independent energy assessments for government agencies, particulary technical and economic evaluation of nuclear power facilities. Con-sultant in this. capacity to Illinois Attorney General; Suffolk County, New York; Schweinfurt, Germany; Governor of Colorado; and Swedish Energy Commission. Also provided studies and testimony for various public interest groups including Center for Law In The Public Interest, Los Angeles; Public Law Utility Group, Baton Rouge, Louisiana; and Union of Concerned Scientists, Cambridge,"Massachusetts. Provided testimony to U.S. Senate/House Joint Committee on Atomic Energy, U.S.

House Committee on Interior and Insular Affairs, California Assembly, Land Use, and Energy Committee, Advisory Committee on Reactor Safe-guards, and Atomic Safety and Licensing Board. Performed comprehensive risk analysis of the accident probabilities and consequences at the Barseback Nuclear Plant for the Swedish Energy Commission and edited, as well as contributed to, the Union of Concerned Scientist's technical review of the NRC's Reactor Safety Study (WASH-1400).

2/76 - 9/76 Consultant, Pro'ect Survival, Palo Alto, California. Volunteer work on Nuc ear Sareguar s Initiative campaigns xn Ca i ornia, Oregon, Washington, Arizona, and Colorado. Numerous presentations- on nuclear power and alternative energy options to civic, government, and college groups. Also resource person for public service presentations on radio and television.

5/75 - 1/76

%fang er - Qualit Assurance Section Nuclear Energy Control and nstrumentation Deoartment, Genera E ectrz.c Comoanv, San Jose,

~pqh'yyd,yd,hd,dq'ph'h a x orna.a. eport to t e Department enera Manager. Deve op and that products produced by the Department meet quality requirements as defined in NRC regulation 10 CFR 50, Appendix B, ASME Boiler and Pressure Vessel Code, customer contracts, and GE Corporate policies and procedures. Product areas include radiation sensors, reactor

t t vessel internals, fuel handling and servicing tools, nuclear plant contxol and protection instrumentation systems, and nuclear steam supply and Balance of Plant contxol room panels.

Responsibile for approximately 45 exempt personnel, 22 non-exempt pexsonnel, and 129 hourly personnel with an expense budget of nearly 4 million dollars and and equipment investment budget of approxi-mately 1.2 million dollars.

11/71 - 5/75

/

Mana er - ualit Assurance Subsection, Manufacturing Section of tomic ower auzoment De axtment, enera ectrz.c ComDan, 'an Jose, Ca izoxnia. Report to the Manager or Manu acturing. Same unctzona an product- responsiblities as in Engagement ><1, except at a lower oxganizational =report level. Developed a quality system which received NRC certification in 1975. The system was also suc-cessfully surveyed for ASME "N" and "NPT" symbol authorization in 1972 and 1975, plus ASME "U" and ".S" symbol authorizations in 1975.

Responsible for from 23 to 39 exempt personnel, 7 to 14 non-exempt personnel, and 53 to 97 hourly personnel.

3/70 - 11/71 Mana er - A plication En ineerin Subsection, Nuclear Instrumentation e artment, enexa r. ectrxc Comoan , San Jose, Ca se e or t e post oraer tecnnxca i ornia. Respon-znter ace wxt arc detect engineers and power plant owners to define and schedule the instrumentation and control systems for the Nuclear Steam Supply and Balance. of Plant portion of nuclear power generating stations. Responsibilities included preparation of the plant instrument list with approximate location, review of interface drawings to define functional design requirements, and release of functional requirements for detailed equipment designs. Personnel supervised included 17 engineers and 5 non-exempt personnel.

12/69 - 3/70 Chairman - E uivment Room Task Force, Nuclear Instrumentation Depart-ment, Genera E ectrx,c Com an , ban ose, a x orna.a. esponsz. e or a specia tas force reporting to tne Department General Manager to define methods to improve the quality and reduce the installation time and cost" of nuclear power plant control rooms. Study resulted in the conception of a factory-fabricated contxol room consisting of signal conditioning and operatox control panels mounted on modular floor sections which are completely assembled in the factory and thoroughly tested for proper operation of interacting devices.

Personnel supervised include 10 exempt personne'l.

- 12/69 I'2/65 Mana er Pro osal En ineerin Subsection, Nuclear Instrumentation e axtment, Genera E ectrxc Comoany, San Jose, Ca x. ornza. Respon-se e or t e app ication o instxumentatxon systems or nuclear power reactors during the proposal and pxe-order"period., Respon-sible for technical review of bid specifications, preparation of

technical bid clarifications and exceptions, definition of material list for cost estimating, and the "as sold" review of contxacts prior to turnover to Application Engineering. Personnel supervised varied from 2 to 9 engineers.

8/64 - 12/65 Sales En ineer, Nuclear Electronics Business Section of Atomic ower uivment Oeoartment, enera E ectrx.c om an, an aose, Ca i ornia. Responsi e for t e y

i review, contract negotiation, d ~ C

• 1 power plants, test reactors, and radiation hot cells. Also respon-sible for industrial sales of radiation sensing systems for measure-ment of chemical properties, level, and density.

10/61 - 8/64 A lication En ineer, Low Volta e Switch ear Department, General E ectric Cpm@an , P i a e xa, Penns vania. Responsi e or the app >cation and design o advance iode an silicon controlled rectifier constant voltage DC power systems and variable voltage dc power systems for industrial applications. Designed, followed manufacturing and"personallly tested in advanced SCR power supply for product introduction at the Iron and Steel Show. Project Engineer for a dc power system for an aluminum pot line sold to Anaconda beginning at the 161XV switchyard and encompassing all the equipment to.,convert the power to 700 volts dc at 160,000 amperes.

9/60 10/61 GE Rotational Tzainin P~to tam Four 3-month assignments on the GE Rotational Training Program for college technical graduates as follows:

a. Installation and Service En . Detroit, Michigan. Installation an startup testing ot t e wor s argest automated hot strip steel mill.

b. Tester - Industr Control - Roanoke, Vir inia. Factory, testing o contro pane s or contro o stee , paper,'ulp, and utility mills and power plants.

c. En ineer - Li ht Milita Electronics - Johnson Cit, New York.

eszgn o groun support equipment or testing t e auto px, ots on the F-105.

d. 'ales En~ineer Morrison, Illinois. Sale of appliance controls inc u xng range timers an rezrxgerator cold controls.

A 3

EDUCATION Bachelor of Science Electrical Engineering, University of Arizona, 1960.

Master of Business Administration, University of Santa Clara, 1969.

PROFESSTONAL AFFILIATION Registered Quality Engineer, License No. QU805, State of California.

Member of Subcommittee 8 of the Nuclear- Power Engineering Committee of the IEEE Power Engineering Society responsible for the preparation and xevision of the following 4 national Q.A. Standards:

a ~ IEEE 498 (ANSI .N45.2. 16), Supplementary Requirements for the Calibration and Control of Measuring and Test Equipment used in the construction and maintenance of Nuclear Power Generating Stations.

b. IEEE 336 (ANSI N45.2.4), Installation, Inspection, and Testing Requirements for Instrumentation and Electric Equipment during the construction of Nuclear Power Generating Stations.

c. IEEE P467 (ANSI N45.2.14), Quality Assurance Program Require-ments for the Design and Manufacture of Class IE Instrumen-tation and Electric Equipment for Nuclear Power Generating Stations.

d. IEEE Draft, Requirements for the Procurement and Storage of Class IE Equipment Replacement Parts.

PERSONAL DATA Birth Date: 7/08/37 Married; three children Health: Excellent PUBLICATIONS AND TESTIMONY

1. Swedish Reactor Safe Stud: Barseback Risk Assessment, 1KB Tec nical Associates, January 1 7 Pu ishe by Swe sh Depart-ment of Industry as Document DSI 1978:1) .

Risks of Nuclear Power Reactors: A Review of the NRC Reactor

2. The Sa an et Stu v MASH-C. Manor w, Ken a, et a, e ate y R. B. Hu bard ox Union of Concerned Scientists, August 1977.

A

~ a ~ ~

3. Testimony of R. B. Hubbard to Advisory Committee on Reactor gafeguards, August.12, 1977, Washington, DC, entitled, Risk Uncertaint Due to Deficiencies in Diablo Can on Qualit ssurance Pro ram an Far. ure to m ement Current NRC Pr actices.

Testimony R. B. Hubbard to United States House of Representatives, Subcommittee on Energy and the Environment, June 30, 1977, Washington, DC, entitled, Effectiveness of NRC Re ulations Modifications to Diablo Can on Nuc ear Unx.ts.

5. Testimony of K. B. Hubbard and G. C. Minor, Judicial Hearings Regarding Grafenrheinfeld Nuclear Plant, March 16 6 17, 1977, Wurzburg, Germany.

6. Testimony of R. B. Hubbard and G. C. Minor before California State Senate Committee on Public Utilities, Transit, and Energy, Sacramento, California, March 23, 1976.

~

7. Testimony of R. B. Hubbard, D. G. Bridenbaugh, and G. C. Minor to the California State Assembly Committee on Resources, Land Use, and Energy, Sacramento, California, March 8, 1976.

8. Testimony of R. B. Hubbard, D. G. Bridenbaugh, and G. C. Minor.

before the United States Congress, Joint Committee on Atomic Energy, February 18; 1976, Washington, DC. (Published by Union of Concerned Scientists, Cambridge, Massachusetts.) Excerpts from testimony published in uote Without Comment, Chemtech, May, 1976.

9. ualitv Assurance: Providin It, Provin It, R. B. Hubbard, Power, Hay, 197

10. In-Core S stem Provides Continuous Flux Map of Reactor Cores, R. B. Hu bard an C. E. Foreman, Power, iVovem er, 1 7.

A 5.

I II

~

I 0 ~

c

ATTACHMENT B AUG1B $ 78 Biographical Data

,Eli Silver Associate Professor, Earth Sciences University of California, Santa Cruz Born June 3, 1942 B.A. Geology, University of California, Berkeley, 1964 Ph.D. Oceanography, Scripps Institution of Oceanography, 1969 Post-Graduate Research Oceanographer, Scripps Institution of 'Oceanography, 1969-1970 Geologist, U. S. Geological Survey, 1970-1974 Assistant Professor, Earth Sciences, University of California, Santa Cruz, 1974-75 Associate Professor, Earth Sciences, University of California, Santa Cruz, 1975-present Chief scientist and/or cruise leader on numerous cruises of Scripps Institution of Oceanography and the U. S. Geological Survey Fellow: Geological Society of America Member: American Geophysical Union, Society of Exploration Geophysicists, Seismological Society of America, AAAS Selected Publications Moore, G. W., and Silver, E. A., 1968, Geology of t:he Klamath River Delta, California: U. S. Geol. Survey Prof. Paper 600-C, p. C144-C148.

Moore, G. N., and Silver, E. A., 1968, Gold distribution on the sea floor off the Klamath Mountains, California:

U. S. Geol. Survey Circ. 605, 9 p.

Silver, E. A., 1969, Late Cenozoic underthrusting of the continental margin of northernmost California:

'Science,- v. 166, p. 1265-1266.

Silver, E. A., 1971, Transitional tectonics and Late Cenozoic structure of the continental margin off northernmost California: Geol. Soc. America Bull., v. 82, no. 1,

p. 1-22.

Silver, E. A., 1971, Tectonics of the Mendocino Triple Junction: Geol. Soc. America Bull., v. 82, p. 2965-2978.

Silver, E. A., Curray, J. R., and Cooper, A. K., 1971, Tectonic development of the continental margin off central Calif.: Geological'Society of Sacramento, Annual Field Trip Guidebook, p. 1-10.

Silver, E. A., 1971, Small plate tectonics of the north-eastern Pacific: Geol. Soc. America Bull., v. 82,

p. 3491-3496.

Silver, E. A., and others, 1972, USGS-IDOE Leg 4, Venezuelan. borderland: Geo times, v. 17, p. 19-21.

Silver, E. A., 1972, Subduction zones: Note relevant to present-day problems of waste disposal: Letter, Nature, v. 239, p. 330-331.

Silver, E. A., 1972, Pleistocene tectonic accretion of the continental slope off Nashington: Mar. Geol.,

v 13 I p 239 249 Jackson, E. D., Silver, E. A., and Dalrymple, G. B., 1972, Hawaiian-Emporer chain and its relation to Cenozoic Circumpacific tectonics: Geol. Soc. America Bull.,

v. 83, p. 601-618.

Dalrymple, G ~ B., Silver, E. A., and Jackson, E. D., 1973, Origin of the Hawaiian Islands: American Scientist, v 61 I no. 3, p. 294-308 ~

Silver, E. A., von Heune, R., Crouch, J. K., 1974, Tectonic significance of the Kodiak-Bowie seamount, chain, Northeastern Pacific: Geology, v. 2, p. 147-150.

Silver, E. A., 1974, Geometrical principles of plate tec-tonics: in San Joaquin Geological, Soc. Short Course, Geological Interpretations from global tectonics with applications for Calif. geology and petroleum exploration, N. R. Dickinson, ed., p. 1-1 to 1-3.

Silver, E. A., 1974, Basin development along translational continental margins: in San Joaquin Geological Soc.

Short Course, Geological interpretations from global tectonics with applications for Calif. geology and petroleum exploration, N. R. Dickinson, ed., p. 6-1 to 6-5.

B-2

Silver, E. A., 1974, Evolution of the San Andreas fault system: in San Joaquin Geological Soc. Short Course, Geological interpretations from global tectonics with applications for Calif. geology and petroleum exploration, W. R. Dickinson, ed., p. 12-1 to 12-5.

Silver, E. A , 1974, Detailed near-bottom geophysical profile across the continental slope off northern California:

U.S. Geol. Survey Jour. of Research, v. 2, p. 563-567.

Silver, E. A., Case, J. E., and MacGillavry, H. J., 1975, Geophysical study of the Venezuelan borderland: Geol.

Soc. America Bull., v. 86, p. 213-226.

Silver, E. A., 1975, Collision events in orogenesis (abs):

13th Pacific Science Congress, Vancouver, Canada.

Silver, E. A., 1975, Collision events in orogenesis: EOS,

v. 56, p. 1066.

Silver, E. A. and Moore, J. C., 1976, A geophysical study of the Molucca Sea collision zone, Indonesia (abstract):

EOS, Trans. AGU, v. 57, p. 1003.

Silver, E. A.', 1977. The Sula spur enigma (abstract): Geol.

Soc. Amer. Abs. with Programs, v. 9, p. 1175-1176.

Silver, E. A., 1977, Are the San Gregorio and Hosgri fault zones a single faul't system'P (Abstract): Geol. Soc.

Amer. Abs. with programs, v. 9, p. 500.

Silver,-E. A., 1978, Geophysical studies and tectonic develop-ment of the continental margin off the western United States, 34'o 48 N: in Geol. Soc. America Memoir, Smith, R. B. and Eaton, G. P., eds., (in press).

Silver, E. A. and Moore, J. C., 1978, The Molucca Sea collision zone, Indonesia: Jour. Geophys. Res., v. 83.

Blake, M. C., Campbell, R. H., Dibblee, T. H., Howell, D. G.,

Nilsen, T. H., Normark, N. R., Vedder, J. G., and Silver, E. A., 1978, Neogene basin formation and hydro-carbon accumulation in relation to the plate tectonic evolution of the San Andreas fault system, California-Amer. Assoc. Petroleum Geol. Bull., March 1978.

Silver, E. A., 1978, The San Gregorio-Hosgri fault zone:

An overview: Calif. Div. Mines and Geol. Special Pub. 137.

Silver, E. A., McCulloch, D. S., and Curray, J. R., 1978, Marine geology and tectonic history of the central California continental margin: Submitted to AAPG.

Bull.

4

~" Y, + E%

0 ~

ATTACHMENT C BZOGRAPBY CLARENCE A. EKL JR.

Social Security Number:

569-34-9229 Address: 2427 S. Armacost Avenue 820 Los Angeles, CaZi foznia 90025 Home 2'elephone:

(223) 473-3061 Bvainess 2'e Zephone:

(223) 825-2020 Date of Birth:

January 5, 1930 - Citizen of the United States Born: Los AngeZes, CaHfornia

, xi~Le: Prop essoz'f Geologp Eaum~tz m: B. S., Stanford University, 2952 lA S., Sta. ford University, 2953 Pn.D., S~-"ord University, 2956 Pa"t ciployment:

Romd Valley Pmgsten Nine, Bishop, CaHfornia, Geologist, 2952 U.S. C~ological Suey (Or gon), Geologist, 1953 Unive sity of Oregon, 1'nstrv tor in Geology, 2954-55 Z~Ze Oil ~n Refining Ccnvany, Geologist, 2955 Stanford University, lnst~mtor in GeoZogp, 2956 Suv..er ~.,pKoyment, V.S. Geological Survey, Geologist, 2972-78 Vniversi='w of California, Los Angeles, Assistant Pz'ofessoz to Professor, 2966 to Present; Chairman, Depa~~.ent of Geology, 9-2-74 to 22-31-76, Acting Chairman, Department of Geophysics and Space Physics 8-2-76 to 12-31-76, Chairman, Depaztment of Eazth and Space Sciences 1-2-77 to 8-32-78 Scholarly Societies:

ZeZZ~ GeologicaZ Society of America Paleontological Society of America Editor Journal of PaZeontology, 1971-72 NalacoZogicaZ Society of CaZi foznia Zonors and Awards:

Zulbright Research Scholaz; 2taly, 2963-64 and 2970-72 invited Lectvwer, PoHsh Academy of Science, 2964

s ~ ~

~ s o gi., ~,

C. A. Hall s I'

1958 Geology and paleontology of the Pleasanton area, Alameda and contra Costa Counties, Calif.: Univ.

Calif. Pub- Geol. Sci., v. Q4, no. 1, p. 1-90, pls.

l-l2, 2. figs; 5 maps.

2 ~ 1958 Gastropod Genus Ceratostoma Geol. Soc. Asser .Bull.,

69, . 12, I . RR~. S 7. (ABII'IIICI'I 3e 1959 The Gast opod, Genus 'Ceratostoma: Jour. Paleontolo~,

v. 33, no. 3, p. 428-430, 3 pls. 1959.

- 1959 Pigeon point Formation of Late Cretaceous age, San Elateo Co. Caliz.: Amer. Assoc. Patrol. Geologists Bull.,

v. 5, no. 12, p. 2855-2859, 1959.

1959 Displaced IO.ocene VG3.luscan Provinces along the'an E

Andreas ault. Pacific Petroleum Geologist Newsletter, Amer. Assoc. Petro3.. Geol., v. 13, no.- 3, p. 4. (ABSTRACT)

6. 1959 Displaced 1 iocene Molluscan Provinces along the San Andreas F"ult, Calif., Geological +(+.Society ofn America r--

ym.x., v. jO, no. 12, pt., p. s s r t n sgt, s s s s.> s ss ss s 7e 1960 Displaceh '.!iocene Molluscan Provinces Along the San 9 d eas Fault,, Calif.: Univ. Cali . Pub.

Geol. Soc.~ v. 3LI, no; 6, p.- 281-308.

8. Ceratos i G .a Herrmannsen, 1%6 (Class Gastropoda);

propose"'dition to the Official list of Generic Ham s. A. Fi. (S) 1088: Bull,. Zoo3.. Homencl., v. 18, pt. 5, p. 336, 1961.

9. Geolog c Yap of California, San Francisco Sheet, Calif. Div. of I4ines, 1961 (Contributor).

3.0. 1962 Displaced Miocene Yiolluscan Provinces along the San Andreas Fault in Guidebook, Geology of'arrizo plains and San Andreas Fault, 1962: pac. Sec. Amer. Assoc.

Petro3.. Geol., p. 20, 1962.-

'I

11. 1962 Displaced Viocene molluscan provinces along the San Andreas Fault, Calif'.: Amer. Assoc. Petro3.. Geol.,

v. 06, no. 10, p. 1952-3.960, 1962.

12. 1962 Evolution of the echinoid genus Astrodapsis: Univ.

Calif. Pub. Geol. Sci., v. 40, no. 2, p. 7-180, 1962. $

1964 Area Arc" lepton;ramnica, a new late ecypo Erom .ze San Luis Obi"po Pegion, Calif'.:

Tertiary'e Jour. paleo., v. 3U, no. 3., p. 87-88, 3.96>i.

C-2

~, I 'yuscaag.

g~0gcI6< ~

I

'as4x cg+51 23 pe3-

~

y964 .

g QXQA 4'la v g5 'Chas

'n Con s x t~ o ~e~ya l~gyn

~ j esca So~e~ ~9 gg Q3 s

. o~ene ~><>>1< pe(X

'5. ~g64 S>~~

g gut C

~gh to the gn ~t'~. 3

~~ana >~g~, d.at'e e+

tos to~a Of MeT~

S

.fr~a>

go 2>>

~ann g>s<

~ t,.

64 Qf 3>

~

$46 Gene y96-

. enus y

~.es 3-9o

>sggo6

'ap go<a~

~

a s ~~

neue e~@SIC

. Zo

'ej.t

+

y6.

~

yips.e nc~'

~'"

hkno pe eT f ' gQG of ' Sc~.> ~gG- g~on ~~

u~+ Geo g.-. gch>no oi<e T,ox+ Ca y, o pu> 0~~sgo ~an~ess, ~ a

+ye'g foss>

age O f the

~ho'gn Coas a~ )on g So ' (~q g

+h ss~ -. b>n gg3->", 's~

QQg oce ns5 S ocen e gcI$ 6 ~ g> 9 V>~ you>

~(>> a neega a gea-

~p haeoon pdacha,. fzo> ~he Z-23-pe 2 Bo She

x9 ~

o the . 0> o ~

f gh.e G

" -.. ~

ggz of at,>on G o>- SocSec ~

c an<8c Zeo3- .

f oman

~ a>

g'ge <an geso zoj SQ

>9~ ofeeCg . ~ of tuSe 2 a .

them p,

~

y967 ~OCM> Geoh

~~51a9 St ~aC 5 qo~g o quad

~ eT ~

yea+t,o4 ~

h C Y .

~

0>isQ o g5-9663> ~c 22-

'ot

~

5.a.

own g6't < <x>>th San guhs gee~

ga$ > gh e Soc ~

y Q,e

~

~ . s Geol 2 Qe >

geboo 0~~so. o Sect> g.. .

~

Co 'Pa~

Gu yes Qu> . gyeyan fo'e> . jgj.nc ~

gC+4 ~

ops~'-9 Co~~' us S.

~ct,use (ir>th - 0>>sg puca

'yg6'7 22'9 ',

thec t~on Sag, r

a. T)e fense Ca-~f

. Gu o.

G oyo~ f ga >tozy.sh og>

" 25- 3-9 Co - Geo> . t,h~Qe Copse of a g<<'on a ~on t,>on>> Q.

3. t,g3 QuQ 0 Qo yQaC

~ ~ pe<an, Sec Su 0'0 26 ~ . tih <a~s >

~yo6< n o . 2 >

~ ~

~ e 1 ~

27- 1970 The Obis~ Formation and as ociat~volcanic rock in.

the Gentle. California Coast Range~- K-Ar'ages and biochronologic signif'icance. Geol. Soc. America ab'stracts with programs, Cordilleran Section, 66th Annual meeting, v- 2, no. 2, (srith D. L. Turner and, R.

C. Surdam).

28.. 1973 Geology of the Arroyo Grande quadrangle, San Luis Obispo Co., Californ a: C"lif- Div. of Nines and .

Geology Nap Sheet 24. ~ ~

29. 1973 Geologic map of the Morro Bay South and port San Luis quadrangles, San Luis Obispo Co., California. U. S.

Survey 1G'11 Map Series. 'eological.

P 3O- 1973- Oligocene and Miocene Felsic Volcanism, Nest Centra3.

California Coast Ranges, Amer,. Geophys. Union Iieeting, Fall, 1973 (abstract} (~rith 8. G. Ernst).

Shell gro;i-~h in Tivela stultorum (Mawr, 1823) and ca11me chione TL'nnaeue, 1(55 Iaiva1via): Annua1 perxoc'city, latitudinal differences and diminution 197'974 ~with age, (rrith >T. A. Dollase and C. E. Corbato).

'Palaeo~eography, Palaeoclimatalogy.. Paleoecology.

v 3.5> p. 33>>61.

32. G ology and Petrology of he Cambria Felsite a Hetr 03.i=ocen Formation 'tTest Central Calif. Coast Ranges.

Geol. Soc. Amer. Bu13 , v. U5> p 523 532 7T. G. Ernst).

'Nith 33 197< Geo" og' I:ao of the Cambria Region, .San Lu- s OD ispo County, California. U. S .,Geological Survey, Miscellaneous F'eld Studies Map 599 in 1974.

\

3)+. 1970 Lati ud, nal variation in shell grosrth patterns of bivalve'mo3~uscs: implications and problems: He@castle Vol.; 1974.

Symposium, 35-'975 Latitudinal variation in shell growth patterns of bivalve moI3.uses: implications and problems. p. 163-173 In Growth Rhythms and the history of the Earth' rotation, G. D. Rosenberg and. S. K. Runcorn eds.

John 3/iley and Sons.

36. 1975 Feldspathic Geodes Hear Black Mountain, Western San Luis Obispo County, California, Geol. Soc. Amer.,

abstracts ~"ith programs, Cordilleran Section, 73.st Annual I,"ecting, March, 1975. (With lT. G. Ernst)

(ABS RACTe)

~

37- 1975 Geologic map of the Cayucos-San Lui" Obispo repion.

U. S- Geol. Surv. Misc. Field Studies Map, M; 686 C-4

~~

hi c geodes near B lack Mo&ta i n, wes tern i 38. 1975 Fe I dsp Luis Obispo County, California: Amer. Min., V. 60, 1105-1112. (with M. G. Ernst)

39. 1975 San Simeon-Hosgri fault system, coastal Cali fornia:

economi c and, env i ronmenta I imp I i cat i ons . U.S.

Geological Survey Open Fi le Rept.,75-533, 12 manuscript pages.

40. 1975 San Simeon-Hosgri fault system,'oastal Cali fornia:

i economi c and env i ronmenta I imp I i cat ons . Sci ence,

v. 190, 'p. 1291-1293.

41. 1976 Geologic Map of the San Simeon-Piedras Blancas Region, San Luis Obispo County, Cali fornia: U.S.

Geo log i ca I Survey Mi sc. Fi e I d Studi es Map, MF 784, scale of I:24,000.

42. 1976 Origin and development of the Lompoc-Santa Haria pull-apart Basin and its relation to the San Simeon-Hosgri Fault, Cali fornia: Geological Society of Amer i ca (ABSTRACT)

IN PRESS Geologic Map of the Santa Haria Val ley Region, Santa" Barbara County, Cali fornia: U.S. Geological Survey.

Misc. Field Studies Map, scale of I:24,000.

IN PRE- Cerozoi c bas'ins, Centra I Ca I i forni a, (Probab PARATION Division of Hines wi I I, publish GSA ly'alifornia Sy-posium papers (see abstract 4'42 for general di'scuss ion) .

r ~

~

{ < ~ q ~

~

ATTACHMENT D

~ p ~

Stephan Alan Graham 2136 Greenwood Dr.

San Carlos, CA 94070 General Born 4/25/50, Evansville, Indiana hhrried 5/27/72, wife-Pmela, 1 child U.S. citizen, military status-lH, foreign language-German Education A.B. Indiana University .

1972 Geology, with Honors M.S. Stanford University 1974 Geology I Eh.D. Stanford Unive sity 1976 Geology Specialization: Sedimentary geology, in particular sedimentary tectonics Thesis: addle Tertiary paleogeography and structural development of the Salinian block, California; Eh.D. committee: W. R. Dickinson (advisor), J. C. Ingle, Jr., B. M. Page Professional Ecperience

l. 1968, 1970: Subsurface mapping, Fritz Operating Co., Ft. Branch, Ind.,

(summers )

2. 1970: X-ray diffractometer technician, Indiana Univ., Bloomington, Ind., (part-time)

3. 1971-1972: Consulting geologist for Peninsula Exploration Co., Corpus Christi, Texas, (part-time )

4. 1972: Associate Instructor, Indiana University Geologic Field Station, Cardwell, hantana, (summer )

5 1973: Research assistant, Stanford University, Stanford, Ca.,

(summer'

6. 1973: Instructor, Stanf'ord Geological Survey, Bridgeport, Ca.,

(summer )

7. 1976: Research Geologist, Exxon Production Research Co.,

Houston, Texas

8. 1,976- Exploration Geologist, Chevron USA Inc., San Francisco, CA Awards, Assistantships, and Fellowships

1. Earth Sciences Freshman Scholarship, Indiana University, 1968 2~ Arthur R. hertz Distinguished Scholarship, Indiana University, 1968-1972 3~ Indiana University Geologic Field Station tuition award, 1969 Standard Oil of'exas undergraduate geology award, 1969, 1970 5~ Best student paper, Rocky Mtn. Section, Geol. Soc. America, 1971

6. Senior faculty scholarship award, 3adiana University, 1972 7 ~ %hi Beta Kappa, 1972

8. National Science Foundation Graduate Fellowship, 1972-1975

~ ~

2 Professional Societies Geologica1 Society of America Sigma Xi Society o Zconomic Paleontologists and Mineralogists Publications Graham, S.A., 1971, Occurrence of middle Cambrian islands in southwest

&ntana: Geol. Soc, America Abs. with Programs, Rocky Mtn. Section, 383-384.

Graham, S.A., and Suttner, L.J., 1974, Occurrence of middle Cambrian islands in southwest leant ~a: %he bhuntain Geologist, v. 11, 71-84.

Graham, S.A., 1974, Remanant magnetization of modern tidal flat sediments from San Francisco Bay, California: Geology, v. 2, 223-226.

Graham, S.A., Dickinson, W.R., and Ingersoll, R.V.> 1975, Himalayan-Bengal model for flysch dispersal in the Appalachian-Ouachita system:

Geol. Soc. America Bu11., v. 86, 4 3, 273-286.

Dickinson, W.R., and Graham, S.A., 1975, Sedimentary environments, depositional systems and stratigraphic cycles in current concepts of depositicnal systems with applications for petroleum geology; W.R. Dickinson, editor:

San Jo~uin Geological Society Short Course, Bakersfield, 1-10.

Graham, S.A., 1975, Tertiary sedimentary tectonics of the central Sa1inian block of California: Geol. Soc. America Abstracts with programs>

v. 7, no. 7, 1089.

Graham, S.A., 1976, Tertiary sedimentary tectonics of the central Salinian block of California: Eh.D. Dissertation, Stanford University, Stanford, California, 510 p.

Graham, S.A., 1976, Tertiary stratigraphy and depositional environments near Indians Ranch, 1hnterey County, California: The Neogene Symposium, Pac. Sect., Soc, Econ. P01eontologists and 5!ineralogists, 125-136.

Grahmn, S.A., 1976, Tertiary stratigraphy and depositional environments near Indians Ranch, bbnterey County, Ca1ifornia: Amer. Assoc. of Mtroleum Geologists Bull. (abs. ), 2181-2182.

Graham, S.A., 1976, San Gregorio Fault as a major right-slip fault of the San Andreas Fault system: Geol. Soc. America Abstracts with Programs,

v. 8, no. 6, 890.

Graham, S.A., Ingersoll, R. V., and Dickinson, W.R., 1976, Common provenance for lithic grains in Carbon'erous from Ouachita t~ountains and Black Warrior Basin: Journal of Sedimentary Petrology, v. 46, 620-632 Dickinson, W.R., Graham, S.A., and Ingersoll, R.V., and Jordan T.Z., 1976p Application of plate tectonics to petroleum geology along the Pacific margin of North America: Aner. Assoc. Petroleum Geologists Bull.

(abs), 2179.

Graham, S.A., and. Dickinson, W.R., 1977, Apparent offsets of onl'and geologic features across the San Gregorio-Hosgri fault trend: Geol. Soc. America Abstracts with Programs, v. 9, no. 4, 424.

Graham, S.A., and Dickinson, W.R., 1978, Apparent offsets of on1and geologic features across the San Gregorio-Hosgri fault trend: Science, v. 199, 179-181. =

D-2

Graham, S.A., and Dickinson, V.R., 1978, Apparent offsets of onland geologic features across the San Gregorio-Hosgri fault trend: Calif. Div. Yiines and Geology Special Report (in press).

Graham, S.A., 1978, Role of the Salinian block in the evolution of the San Andreas fault system: Amer. Assoc. Petroleum Geologists Bull.,

v. 62, g ll (in press).

b Telephone (415) 894-0308 (office 8:00 AM - 4:00 PM.)

(415) 595-2036 (home )

~ ~

Curriculum Vitae - Wm. R. Dickinson Born: Nashville, Tennessee, Oct. 26, l931 Degrees (all Stanford University):

B.S., Pet. Engr. 1952 USAF, 1952-1954 M.S., Geology 1956 Ph.D., Geology 1958 Faculty Positions (all Stanford Univ.):

Acting Assistant Professor 1958-60 Assistant Professor 1960-63 Associate Professor 1963-68 Professor 1968-Present Guggenheim Fellow 1965 Articles in Science, Nature,'eol. Soc. America Bull., Jour. Geophys.

Research, Am. Jour Sci., Am. Assoc. Petroleum Geologists Bull., Jour.

Sediment. Petrology, Sediment. Geology, Tectonophysics, Earth and Planetary Sci. Lettrs., Rev. Geophysics and Space Physics, Can. Jour.

Earth Sci.

Member of Geol. Soc. America (Fellow), Am. Assoc. Petroleum Geologists, Am. Geophys. Union, Soc. Econ. Paleontologists and Hineralogists, Nat. Assoc. Geology Teachers, Am. Assoc. Adv. Sci.

Chairman, Cordilleran Sec., Geol. Soc. America (1974-1975);

President, Peninsula Geol. Soc. (1977-1978);

Councillor, Geol. Soc. America (1977-1980).

A. I. Levorsen Memorial Award, Pac. Sec., Am. Assoc. Petroleum Geologists (1978-1979) .

Ma or Conference Partici ation 1966 speaker, Symposium on Circum-Pacific Orogenesis, Pacific Science Congress, Tokyo, Japan.

1967 co-convener, Joint USGS-Stanford'Conference on Geologic Problems of San Andreas Fault System, Stanford University.

1967 - speaker, IUGG-IAV Conference on Andesites, Oregon Institute for Volcanology.

1969 speaker, Andesite Symposium, Volcanic Studies Group, Geological Society of London.

1969 - convener, GSA Penrose Conference on Plate Tectonics and Orogenic Belts, Asilomar, California.

1970 co-organizer, Symposium on Cretaceous Geology of Central California, GSA Cordilleran Section Meeting, Hayward, California,.

~

( ~ ~ ~ ~

1971 co-organizer and speaker, NAS Symposium on Plate Tectonics, Washington, D.C.

1971 keynote speaker, Symposium on Petrology and Geochemistry of Island Arcs in Relation to Tectonic Environment, Pacific Science Congress, Canberra, Australia.

1971 organizer and keynote speaker, Symposium on Plate Tectonics in Geologic History, National GSA meeting, Washington, D.C.

1972 speaker, Carnegie Institute Conference on Plate Tectonics and of Continents, Airlie, Virginia. the'volution 1972 speaker, Joint NSP-Wisconsin Conference on Ancient and Modern Geosynclinal Sedimentation, Madison, Wisconsin.

1973 convener, SEPM Research Symposium on Tectonics and Sedimentation, AAPG-SEPM Nat. Mtg,, Anaheim, California.

1974 speaker, GAC Symposium on Volcanic Geology and Mineralization in the Canadian Cordillera, Vancouver, Canada.

1974 convenor and speaker, San Joaquin Geological Society Short Course on Plate Tectonics and Petroleum Geology, Bakersfield, California.

1975 convenor and speaker, San Joaquin Geological Society Short Course o' Depositional Systems and Petroleum Geology, Bakersfield, California.

1975 Speaker, Symposium on Circum-Pacific Magmatism, Metamorphism, and Sedimentation, Pacific Science Congress, Vancouver, Canada.

1976 invited speaker, Ewing Symposium of Lamont-Doherty Geological Observatory, Harriman, New York.

1976 convenor and speaker, Symposium on Pre-Tertiary of Blue Mountains Province, GSA Cordilleran Section Meeting, Pullman, Washington.

1976 instructor, AAPG Short Course on Plate Tectonics and Hydrocarbon Accumulation, AAPG National Meeting, New Orleans, Louisiana.

1976 speaker, SEG Short Course on Plate Tectonics and Sedimentary Basins, SEG National Meeting, Houston, Texas.

1977 speaker, Symposium on Paleozoic Paleogeography of the Pacific Coast, Pacific Section SEPM Meeting, Bakersfield, California 1977 speaker, AAPG Short Course on Continental Margins, AAPG National Meeting, Washington, D.C.

1978 keynote speaker, International Geodynamics Conference on the Western Pacific, Tokyo, Japan.

E-2

Is 1 l 1978 speaker, Symposium on Mesozoic Paleogeography of the Pacific Coast, Pacific Section AAPG Meeting, Sacramento, California.

E-3

List of Publications in Geolo ical Science b William R. Dickinson WRD, 1958, Mesozoic marine clastic rocks of volcanic derivation in southwestern Grant County, Oregon (abs}: Geol. Soc. America Bull., v. 69, p. 1554.

WRD, 1959, Structural relationships of Church Creek and Willow Creek Faults, Santa Lucia Range, California (abs.): Geol. Soc. America Bull., v. 70,

p. 1715.

1960, Geology of the Izee area, Grant County, Oregon (abs): Dissert. Abs.,

v. 20, no. 11 (1958 Ph.D).

1960, Petrology of Jurassic marine tuffs, central Oregon (abs)': Geol. Soc.

America Bull., v. 71, p. 2056.

1961, Jurassic andesitic province along the Pacific margin of North America (abs): Geol. Soc. America Abs. for 1961, p. 19.

1962, Brecciated serpentine extrusion on Table Mountain in central California Coast Ranges (abs).: Geol. Soc. America Abs. for 1962, p. 34.

1962, Marine sedimentation of clastic volcanic strata (abs): American Assoc. Petroleum Geologists Bull., v. 46, p. 263.

1962, Hetasomatic quartz keratophyre in central Oregon: Am. Jour. Sci.,

v. 260, p. 249-266.

1962, Petrology and diagenesis of Jurassic andesitic strata in central Oregon: Am. Jour. Sci., v. 260, p. 481-500.

1962, Petrogenetic significance of geosynclinal andesitic volcanism along the Pacific margin of North America: Geol. Soc. America Bull., v. 73,

p. 1241-1256.

1963, Tertiary stratigraphic sequence of the Hancock Ranch area, Monterey and Kings Counties, California: Pac. Sec. Am. Assoc. Petroleum Geologists-Soc. Econ. Paleontologists and Hineralogists Ann.Field Trip Guidebook to Geology of Salinas Valley and San Andreas Fault, p. 47-53.

WRD and L. W. Vigrass, 1964, Pre-Cenozoic history of Suplee-Izee district, Oregon: . implications for geosynclinal theory: Geol. Soc. America Bull.

v. 75, p. 1037-1044.

WRD, 1965, Folded thrust contact between Franciscan rocks and Panache Group in the Diablo Range of central California (abs): Geol. Soc. America Special Paper 82, p. 248-249.

WRD and L. W. Vigrass, 1965, Mesozoic history of Suplee-Izee district, central Oregon (abs): Geol. Soc. America Special Paper 82, p. 325.

WRD and J. G. Smith, 1965, Geological relations of the Koroimavua Group in northwest Viti Levu: Fiji Geol.. Survey Dept. Note 121, 4 p.

WRD and J. G. Smith, 1964, Geological road log from Nandi International Airport to the Nausori Highlands: Fiji Geol. Survey Dept. Note 122, 6 p.

E-4

~ ~ ~

Publications, William R. Dickinson Page two Smith, J.G. and WRD, 1965, A geological reconnaissance of the southern Ya'sawa Islands: Fij i Geol. Survey Dept. Note 125, 6 p.

WRD and L.W. Vigrass, 1965, Geology of the Suplee-Xzee area, Crook, Grant, and Harney Counties, Oregon: Ore. Dept. Geology and Mineral Industries Bull.

No. 58, 109 p.

WRD, 1965, Tertiary stratigraphy of the Church Creek area,'onterey County, California: Calif. Div. Mines and Geology Special Rpt. 86, p. 25-44.

WRD, 1966, Problems of stratigraphic nomenclature in Fiji (South-West Pacific Geological Survey Conference Paper): Fiji Geol. Survey 'G. S. Note 9/66, 10 p.

WRD, 1966, Table Mountain serpentinite extrusion in California Coast Ranges:

Geol. Soc. America Bull., v. 77, p. 451-472.

WRD, 1966, Structural relationships of San Andreas fault system, Cholame Valley and Castle Mountain Range, California: Geol. Soc. America Bull., v. 77,

p. 707-726.

WRD, 1966, Petrography of specimens from the Mamanutha Group: Fiji Geol. Survey Dept. G. S. Note 20/66, 5 p.

WRD and D.R. Lowe, 1966, Stratigraphic relations of phosphate- and gypsum-bearing upper Miocene strata, upper Sespe Creek, Ventura County, California:

Am. Assoc. Petroleum Geologists Bull., v. 50, p. 2464-2470.

WRD, 1967, Circum-Pacific andesite types (abs): Am. Geophys. Un. Trans., v. 48,

p. 253.

WRD and Trevor Hatherton, 1967, Andesitic volcanism and seismicity around the Pacific: Science, v. 157, p. 801-803.

WRD, 1967, Tectonic development of Fiji: Tectonophysics, v. 4, p. 543-553.

WRD, 1967, Problems M stratigraphic nomenclature in Fiji (abs): N.Z. Jour.

Geology and Geophysics, v. 10, p. 1181-1182.

WRD, 1968, Circum-Pacific andesite types: Jour. Geophys. Res., v. 73,

p. 2261-2270.

WRD and Arthur Grantz (eds), 1968, Proceedings of conference on geologic problems of San Andreas fault system: Stanford Univ. Pub. Geol. Sci., v. 11, 375 p.

WRD, 1968, Sedimentation of volcaniclastic strata of the Pliocene Koroimavua Group in northwest Viti Levu, Fiji: Am. Jour. Sci. v. 266, p. 440-453.

I Hatherton, Trevor and WRD, 1968, Andesitic volcanism and seismicity in New Zealand: Jour. Geophys. Res., v. ?3, p. 4615-4619.

WRD, M.J. Rickard, F. X. Coulson, J. G. Smith, and R.L. Lawrence, 1968, Late Caenozoic shoshonitic lavas in northwestern Viti Levu, Fiji: Nature,

v. 219, p. 148.

E-5

Public ons, William R. Dicki~>>;on Page t)tree WRD, 1968, Comparison of California's Franciscan assemblage and Great Valley sequence to New Zealand's axial and marginal facies (abs): Geol. Soc.

America Special Paper 115, p. 322.

WRD, 1968, Singatoka dune sands, Viti Levu, Fiji: Sed. Geology, v. 2,

p. 115-124.

WRD, 1968, Blend of teaching and research (letter): Science, v. 162, p. 1221.

Noble, D.C., WRD, and Clark, M.M., 1969, Collapse caldera in the Little Walker area, Mono County, California (abs): Geol. Soc. America Special Paper 121, p. 536-537.

Rich, E.I., R.W. Ojakangas, WRD, and Win Swe, 1969, Sandstone petrology of Great Valley sequence, Sacramento Valley, California (abs): Geol. Soc.

America Special Paper 121, p. 550.

WRD, R.W. Ojakangas, and R.J. Stewart, 1969, Burial metamorphism of the late Mesozoic'reat Valley sequence, Cache Creek, California: Geol. Soc.

America Bull., v. 80, p. 519-525.

WRD, 1969, Evolution of calc-alkaline rocks in the geosynclinal system of .

California and Oregon, p. 151-156 in McBirney, A.R. (ed), Proceedings of andesit'e conference: Ore. Dept. Geology and Mineral Industries Bull.

65, 193 p.

In Pac. Sec. Soc. Econ. Paleontologists and Mineralogists, 1969, Field Trip Guidebook (WRD, ed): Geologic setting of upper Miocene gypsum and phosphorite deposits, upper Sespe Creek and Pine Mountain, Ventura California, 91 p.: 'ounty, (a) WRD (p. 1-24), Geologic problems in the mountains between Ventura and Cuyama.

(b) WRD (p. 49-55), Miocene stratigraphic sequence on upper Sespe Creek and Pine Mountain.

(c) WRD (p. 63), quaternary terrace gravels and colluvium on south side of Pine Mountain.

(d) WRD (p. 68-77), Road log, Ojai. to Ozena.

Hatherton, Trevor and WRD, 1969, The relationship between andesitic volcanism and seismicity in Indonesia, the Lesser Antilles, and other,i.sland arcs:

Jour. Geophys. Res., v. 74, p. 5301-5310.

Swe, Win and WRD, 1970, Sedimentation and thrusting of late Mesozoic rocks in the Coast Ranges near Clear Lake, California: Geol.'oc. America Bull.,

v. 81, p. 165-188.

WRD, 1970, Tectonic setting and sedimentary petrology of the Great Valley Sequence (abs): Geol. Soc. America Abs. with Progs.; v. 2, p. 86-87.

Gilbert, W.G. and WRD, 1970, Stratigraphic variations in sandstone petrology, Great Valley Sequence, central California coast: Geol. Soc. America Bull., v. 81, p. 949-954.

E-6

~ ~

Publi .ons, Wflliam k. Dickinson Page four l

WRD and Page, B.M., 1970, Central California Coast Ranges: Guide to Field Trip No. 1, Cordilleran Sec., Geol. Soc. America Ann. Mtg. 1970, 25 p.

WRD, 1970, The new global tectonics (report: 2nd Penrose Conference): Geotimes,

v. 15, no. 4, p. 18-22.

WRD l1970, Global tectonics (report: 2nd Penrose Conference): Science, v. 168,

p. 1250-1259.

WRD, 1970, Interpreting detrital modes of graywacke and arkose: Jour. Sed.

Petrology, v. 40, p. 695-707.

1970, Relations of andesitic volcanic chains and granitic batholith belts to the deep structures of orogenic arcs: Geol. Soc. London Proc.,

no. 1662, p. 27-30.

1970, Geology and geologists in regional planning (abs): Geol. Soc.

America Abs. with Progs., v. 2, p. 738-739.

WRD, 1970, Geology for the Masses: Jour. Geol. Education, v. 18, p. 194-197.

1970 970, Relations of andesxtes, granites, and derivative sandstones to arc-trench tectonics: Rev. Geophys. and Space Phys., v. 8, p. 813-862; WRD, 1971, Detrital modes of New Zealand" graywackes: Sed. Geology, v. 5,

p. 37-56.

1971, Plate tectonics (developments during 1970): Geotimes, v. 16, p. 21.

1971, Plate tectonic models of geosynclines: Earth and Planet. Sci.

Lettrs., v. 10, p.,165-1?4.

1971, Clastic sedimentary sequences deposited in shelf, slope, and trough settings between magmatic arcs and associated trenches: Pac. Geology,

v. 3, p. 15-30.

WRD 19?9?1, Plate tectonic models for orogeny at continental margins: Nature,

v. 232, p. 41-42.

WRD, 1971, Complementarity (letter): Science, v. 173, p. 1191-1192.

WRD, 1971, Ecological questionnaire (letter): Natural History, v. 80, no. 2,

p. 101.

WRD 71 19971, Reconstruct@on R of past arc-trench systems from petrotectonic assemblages in island arcs (abs): 12th Pac. Sci. Congr. Proc., v. 1,

p. 445.

WRD, 1971, Plate tectonics in geologic history: Science, v. 174, p. 107-113.

WRD, 1971, Evidence for plate tectonic regimes in the past: Geol. Soc.

America Abs. with Prog., v. 3, p. 544.

WRD and W.C. Luth, 1971, A model for plate tectonic evolution of mantle layers:

Science, v. 174, p. 400-404.

E-7

Publicana, William R. Dickinr~nn Page five WRD, D.S. Cowan and R.A. Schweickert, 1972, Test of new global tectonics (discussion):- Am. Assoc. Petroleum Geologists Bull., v. 56, p. 375-384.

WRD, 1972, The Earth Sciences (second edition), A.N. Strahler (review): Am.

Geophys. Un. Trans. (EOS), v. 53, p. 258-260.

Wright, R.M. and WRD, 1972, Provenance of Eocene volcanic sandstones in eastern Jamaica; a preliminary note: Carib. Jour. Sci., v. 12, p. 107-113.

WRD, 1972, Plate tectonics symposium (preface): Am. Jour. Sci., v. 272,

p. 549-550.

WRD, 1972, Evidence for plate-tectonic regimes in the rock record: Am. Jour.

Sci., v. 272, p. 551-576.

WRD, 1972, Dissected erosion surfaces in northwest Viti Levu, Fiji: Zeitschr.

f. Geomorph. N.F., v; 16, p. 252-267.

Hedge, C.E., Z.E. Peterman, and WRD, 1972, Petrogenesis of lavas from Western Samoa: Geol. Soc. America Bull., v. 83, p. 2709-2714.

WRD and E.I. Rich, 1972, Petrologic intervals and petrofacies in the Great Valley sequence, Sacramento Valley, California: Geol. Soc. America Bull.,

v. 83, p. 3007-3024.

Mader, G.G., E.A. Danehy, J.C. Cummings, and WRD, 1972, Land use restrictions along the San Andreas fault in Portola Valley, California, p. 845-858 in Sherif, M.A. and R.C. Bostrom (eds), Proceedings of the International Conference on Microzonation fox Safer Construction, Seattle, Wash., 987 p.

WRD, 1973, Tettonica a zolle e catene montuose, art. 10, p. 190-'200 in Enciclopedia della scienza e della tecnica 73: Edizioni scientifiche e techniche, Mondadori, Milano, Italy.

WRD, 1973, Widths of modern arc-trench gaps proportional to past duration of igneous activity in associated magmatic arcs: Jour. Geophys. Res., v. 78,

p. 3376-3389.

WRD, 1973, Reconstruction of past arc-trench systems from petrotectonic assemblages in the island arcs of the western Pacific, p. 569-601 in Coleman, P.J.'ed), The western Pacific; island arcs, marginal seas, geochemistry: Univ. Western Australia Pxess, Perth, 601 p.

WRD, 1974, Review of arc volcanism (abs): Geol. Assoc. Canada Cordilleran Sec.

Programme and Abstracts, p. 9-10.

In WRD (ed), 1974, Geologic interpretations from global tectonics with applica-tions for California geology and petroleum exploration: San Joaquin Geological Society Short Course, Bakersfield, 75 p.

(a) WRD (p. 2-1 to 2-5), Geologic implications of plate tectonics.

(b) WRD (p. 9-1 to 9-6), Plate tectonics and sedimentary basins.

(c) WRD (p. 15-1 to 15-4), Plate tectonics andmigration of petroleum.

E-8

Publica s, William R. Dickinson Page six Noble, D.C., D.B. Slemmons, M.K. Korringa, WRD, Yehya Al-Rawi, and E.H. McKee, 1974, Eureka Valley Tuff, east-central California and adjacent Nevada:

Geology, v. 2, p. 139-142.

WRD, 1974, Sedimentation within and beside ancient and modern magmatic arcs,

p. 230-239 in Dott, R.H., Jr., and R.H. Shaver (eds), Modern and ancient geosynclinal sedimentation: Soc. Econ. Paleontologists and Mineralogists Special Pub. No. 19, 380 p.

Baldwin,. Brewster, P.C. Coney, "and WRD, 1974, Dilemma of a Cretaceous time scale and rates of sea-floor spreading: Geology, v. 2, p. 267-270.

WRD, 1974, Subduction and oil migration: Geology, v. 2, p. 421-424.

WRD, 1974, Plate tectonics and sedimentation, in Dickinson, W.R. (ed), Tectonics and sedimentation: Soc. Econ. Paleontologists and Mineralogists Special Pub. No. 22, p. 1-27.

WRD, 1974, Island arcs; Japan and its environs (review): Jour. Geology v. 82,

p. 529.

WRD, 1975, Potash-depth (K-h) relations in continental margin and intraoceanic magmatic arcs: Geology, v. 3, p. 53-56.

In WRD (ed), 1975, Current concepts of depositional systems with applications for petroleum geology: San Joaquin Geological Society Short Course, Bakersfield, 105 p.

(a) WRD and S.A. Graham (p. O-l to 0-10), Sedimentary environments, depositional systems, and stratigraphic cycles.

(b) WRD (p. 1-1, to 1-16), Fluvial sediments of stream valleys and alluvial fans.

(c) WRD (p. 5-1 to 5-8), Deltaic deposits and cyclothems.

(d) WRD (p. 12-1 to 12-4), Hydrocarbon occurrences in relation to depositional systems.

Graham, S.A., WRD, and Ingersoll, R.V., 1975, Himalayan-Bengal model for flysch dispersal in Appalachian-Ouachita system: Geol. Soc. America Bull.,

v. 86, p. 273-286.

WRD, 1975, Problems of pre-Tertiary tectonic correlations across the Pacific Northwest (abs): Geol. Soc. America Abs. with Progs., v. 7, p. 604.

WRD, 1975, Geology and oil (review): Science, v. 189, p. 133-134.

WRD, 1975, Time-transgressive tectonic contacts bordering subduction complexes (abs): Geol. Soc. America Abs. with Progs., v. 7, p. 1052.

Snyder, W.S., WRD, and M.L. Silberman, 1975, Tectonic implications of space-time patterns of Cenozoic magmatism in the western United States (abs):

Geol. Soc. America Abs. with Progs., v. 7, p. 1279.

E-9

4 4 ~

Public ns, William R. Dickinson Page seven WRD, 1975, Sedimentary basins developed during evolution of Mesozoic-Cenozoic arc-trench system in western North America (abs): 13th Pacific Sci.

Congr. Abs., p. 397-398.

N WRD and W.S. Snyder, 1975, Geometry of triple junctions and subducted litho-sphere related to San Andreas transform activity (abs): Am. Geophys.

Un. Trans. (EOS), v. 56, p. 1066.

WRD, K.P. Helmold, and J.A. Stein, 1976, Paleocurrent trends and petrologic variations in Mesozoic strata near South Fork of John Day River, central Oregon (abs): Geol. Soc. America Abs. with Progs., v. 8, p. 368-369.

WRD, 1976, Sedimentary basins developed during evolution of Mesozoic-Cenozoic arc-trench system in western North America: Can. Jour. Earth Sci., v. 13,

p. 1268-1287.

Snyder,,W.S., WRD, and Silberman, M.L., 1976, Tectonic implications of space-time patterns .of Cenozoic magmatism in the western United States: Earth Planet. Sci. Lettrs., v. 32, p.91-106.

Graham, S.A., R.V. Ingersoll, and WRD, 1976, Common provenance for lithic grains in Carboniferous sandstones from Ouachita -Mountains and Black Warrior Basin: Jour. Sed. Petrology, v. 46, p. 620-632.

WRD, 1976, Plate tectonics and hydrocarbon accumulation: Am. Assoc. Petroleum Geologists Continuing Education Course Note Ser. No. 1, 61 p.

Graham, S.A. and WRD, 1976, San Gregorio fault as a major right-slip fault of the San Andreas fault system (abs): Geol. Soc. America Abs. with Progs.,

v. 8, p. 890.

Ingle, J.C., Jr., S.A. Graham,, and WRD, 1976, Evidence and implications of world-wide late Paleogene climatic and eustatic events (abs): Geol. Soc.

America Abs. with Progs., v. 8, p. 934-935.

WRD, 1976, The way the earth works; an introduction to the new global geology and its revolutionary development (review): Jour. Geology, v. 84, p. 502.

Casey, T.A.L. and WRD, 1976, Sedimentary serpentinite of the Miocene Big Blue

. Formation near, Cantua Creek, California (abs): Am. Assoc. Petroleum Geologists Bull., v. 60, p. 2177.

WRD, S.A. Graham, R.V. Ingersoll, and T.E. Jordan, 1976, Applications of plate tectonics to petroleum geology along the Pacific margin of North America (abs): Am. Assoc. Petroleum Geologists Bull., v. 60, p. 2179.

Casey, T.A.L. and WRD, 1976, Sedimentary serpentinite of the Miocene Big Blue Formation near Cantua Creek, California, in Fritsche, A.E. H. Ter Best, Jr.,

and W.W. Wornardt (eds),. The Neogene Symposium: Pac. Sec. Soc. Econ.

Paleontologists and Mineralogists Ann. Mtg., p. 65-74.

WRD, 1977, Fossil fuels and continental drift: Basterfield Lec. Ser. No. 19, Univ. Regina, Saskatchewan, 16 p.

Publf c ons, William R. Dickinson Page e5 ght Graham, S.A. and WRD, 1977, Apparent offsets of on-land geologic features across the San Gregorio-Hosgri fault trend (abs): Geol. Soc. America Abs. with Frogs., v. 9, p. 424.

Ingersoll, R.V., E.I. Rich, and WRD, 1977, Great Valley Sequence, Sacramento Valley: Cordilleran Sec. Geol. Soc. America Field Trip Guide, 73 p.

WRD, 1977, Paleozoic plate tectonics and the evolution of the Cordilleran continental margin, in Stewart, J.H., C.H. Stevens, and A.E. Fritsche (eds), Paleozoic paleogeography of the western United States: Pacific Sec. Soc. Econ. Paleontologists and Mineralogists Pacific Coast Paleo-geography Symp. 1, p. 137-156.

WRD and D.R. Seely, 1977, Forearc stratigraphy and structure: 9th Ann.

Offshore Technology Conf. Paper 2889, Houston, Tex., p. 101-106.

D.R. Seely and WRD, 1977, Structure and stratigraphy of forearc regions:

Am. 'Assoc. Petroleum Geologists Continuing Education Course Note Series No. 5, p. Cl-C23.

WRD and D.R. Seely, 1977, Stratigraphy and structure of compressional continental margins (abs): Am. Assoc. Petroleum Geologists Bull.,

v. 61, p. 781.

WRD, 1977, Tectono-stratigraphic evolution of subduction-controlled sedimentary assemblages, in Talwani, Manik and W.C.Pitman III (eds), Island arcs, deep sea trenches, and back-arc basins: Am. Geophys. Un. Maurice Ewing Ser. 1, p. 33-40.

WRD, 1977, Subduction zones: Earth Science Rev., v. 13, p. 70 71 Packer, D. R., >TRD, and K.M.Nichols, 1977, Memorial to Marjorie K. Korringa, 1943-1974: Geol, Soc. America Memorials, 3 p.

WRD, 1977, Subduction tectonics in Japan: Am. Geophys. Un. Trans. (EOS),

v. 58, p. 948-952.

WRD'nd W.S. Snyder, 1977, Inferred plate tectonic setting of classic Laramide orogeny (abs): Geol. Soc. America Abs. with Progs., v. 9, p. 950.

Graham, S.A. and WRD, 1978, Evidence for 115 kilometers of right slip on the San Gregorio-Hosgri fault trend: Science, v. 199, p. 179-181.

Howard, A.D. and WRD, 1978, Volcanic environments, chap. 9 in Howard, A.D.

and Irwin Remson (eds.), Geology in environmental planning: McGraw-Hill, N.Y., p. 246-274.

WRD and T. P. Thayer, 1978, Paleogeographic and paleotectonic implications of Mesozoic stratigraphy and structure in the John Day inlier of central Oregon, in Howell, D.G. and K.A. McDougall (eds), Mesozoic paleogeography of the western United States: Pacific Sec. Soc. Econ. Paleontologists and Mineralogists Pacific Coast Paleogeography Symposium 2, p. 147-162.

4 I'

l

ublished in "San Gregory-.io-1 ~

s'

~I ~

Xn press, to be Hosgri Fault Z California," edited by E.A. Silver e W. Newmark, Calif. Div. of Mines & Geology, Special Report 137.

The San Gregorio-Hoser i Fault Zone: An Qverv iew Eli A. Silver Earth Sciences Board University of California Santa Cruz, CA 95064 The San Gregorio-Hosgri fault zone is part of the larger San Andreas fault system in Cali.fornia. that forms the major locus of shear due to movement between the Pacific and North

'American plates. An enormous amount of effort has been and is presently being devoted to study of the San Andreas fau1.t it elf, and in recent years detailed quantitative knowledge of offset history, se'ismici', and present-day'ovement has increased dramatically (see for example Kovach and Nur, 1973; Crowell, 1975; Dickinson and Gr ntz, 1968) .

The extent of our knowledge of other faults of t: he San Andreas system is much less complete, due in part to the lower frequency of great earthquakes and smaller offset on subsidiary faults (and th re fore, perhap, lesser interest in these faults) .

/'Anotl>er reason may be the location of some of the subsidiary faults. The San Gregorio-Hoseri fault zone is located along the coastline south of San Francisco for a length of nearly 400 km, and much of it lies just offshore where it is difficult to study. Major outstandin., problems of this fault zone include the det:ails of fault location, continuity between the San Gregorio and Hosgri f'auld segments, of fset history on each segment, evidence for Ho1ocene movement:s, and sei. i'oicity, These

1

~ ~

~ e 4 I problems have'mportance both for their tectonic implications and their bearing on analysis of seismic hazard. for coastal deveLopment and power-plant siting.

The papers in this volume were presented as part of a symposium on the San Gregorio-Hnsgri fault zone at the Cordilleran section meeting of the Geological Society of Am rica

, in Sacramento in April, 1977. Not all of those papers. are

'eproduced here but those which follow give a good overview of the present state of knowledge of this fault zone.

Clark and Brabb discuss the detailed stratigraphy on either r side of the San Gregorio fault in its type area. Their careful observations of fundamental stratigraphic differences, imply significant differences in sedimentation and tectonic history on either side of the fault. Graham and Dickinson use this

'I and other regional data to infer up to 115 km of right lateral offset. on, the fault since Miocene time. This figure is larger than an earlier suggestion of SO to 90 km (Siver, 1974) based on offset basement terranes using offshore geophysical control.

~ ~

An estimate of 80 to 100 lan of post Miocene right Lateral A

offset on the Hosgri fault (Hall, 1975) ties rather nicely with the above estimates for the San Gregorio se~ent, but the Hosgri estimate has been questioned (Hamilton and Villingham, 1977). Hall (this volume) briefly addre ses these questions and proposes a pull-apart origin fox'he Santa Maria basin onshore.

The question of continuity of the San Grcgorio-IIosgri fault zone focuses on four problem areas: Point Sur, Cape San F-2

~ ~

Martin, .San Simeon, and south of Point Sal (Fig. 1). The Point Sur region is discussed in detail by Graham and Dickinson.

Their interpretation that the San Gregorio probably connects with the Sur fault is supported by detailed gravity studies (Woodson, 1973) and argues against a previous suggestion that the main San Gregorio fault trace turns inland south of Monterey to join the Palo C'olorado fault (Greene and others, 1973} .

Hall (1975) first suggested that the San Simeon fault is part of the Hosgri fault zone (Fig. 2) . The detailed connection between the Hosgri and San Simeon faults has not been established and some maps show an 'en-echelon offset between these faults (Hall, 1975; McCulloch and others, 1977) . The San Simeon (Hosgri) segment trends offshore to the north toward Cape San Martin (Fig. 2}. Recently flown aexomagnetic data (USGS-Calif.

Division of Hines and Geology unpublished data) reveal a high amplitude anomaly trending northwest across Cape San Martin and seem to require the Hosgri-San Simeon fault either to bend around the anomaly (Fig. 2) or to step 0 hn inland to a fault bounding the east side of the anomaly. If the fault bends around this anomaly it could join a major off hore fault north of Cape San Martin (McCulloch and others, 1977} that trends toward the'Sur fault (Fig. 2). HcCulloch and others (1977)

(their Fig. 2) show a northwest trending fault west of Point Sur (Fig. 1) which they extend southeastward to the coast; cutting across and separating the flosgri and Sur faults. This interpretation would imply a definite lack of continuity between

t'e San Gregorio and.Hosgri faults in this area. However, their northwest trending fault must cross a high amplitude magnetic anomaly that lies parallel to the coast (anomaly M

bounded by -1.5 nT contour in Fig. 2) and this anomaly shows no evidence of a crosscutting structure. The anomaly also trends parallel to the Sur and Hosgri faults and may be caused by serpentine intrusions along the fault. Structural relations in this nearshore area are obscured by surface slumping (NcCulloch and others. - their Fig. 2), and T. conclude that the bulk of evidence at present favors or at least allows continuity between the Sur and Hosgri faults.

The southern extension of the Hosgri is also in dispute.

YicCulloch and others (1977) map the fault south of Pt. Argukllo, but Hamilton and Hillingham (1977), using much the same data, map it no farther south than offshore Point Sal. Either version raises geometrical problems of ending a fault with approximately 100 km of late Cenozoic.c 'lateral offset. Uarious solutions to this problem have been proposed in oral communi-

'cations, including a bend of the fault into the Transverse ranges where the motion would be taken up in compression (D.

NcCulloch, oral commun., 1977; llamilton and Hillingham, 1977) or an offs'et of the fault by east-trending faults in tho Santa Barbara region (J. Crouch, oral commun., 1976) . Satisfactory field docum ntation, howe.vcr, has not been reported and this remains an out tanding structural problem.

Holocene movemcnt., are well documcntcd for the San Grcgorio faul t (Heber and Iajoie, 1977; Copper smitl> and Griggs, this

1

~I L ~ ~

volume), and studies of seismicity confirm the present-day activity on both the Hosgri and San Gxegorio segments (Gawthrop, 3.975 and this volume) . This information is critical to any planned development along the central California coast because the San Gregorio-Hosgri is very nearly a coastline fault over most of its length.

. The San Gregorio-Hosgri appears to b the'argest of the 4

subsidiary 'faults within the San Andreas system, both in length

~

and offset. Other faults, such as the Hayward-Calaveras and Rinconada have lesser documented offset but also play an

/

important role in the tectonic development of the California coast ranges and are deserving of intensive study.

F-5

References Cited Crowell, J. C. (Ed.), 1975, San Andreas fauLt .in southern California: California Division of Hines and Geology Special Report 118, 272 p.

Dickinson, W. R., and Grantz,, A. (Eds.), 1968, Proceedings

. of the conference on geologic problems of San Andreas fault system'Stanford Univ. Pubs. Geol. Sci., v. 11, 374 p.

Gatothrop, William,'975, Seismicity of the central California coastal'region: U.S. Geol. Survey Open-file Report 75-134, 87 p.

\

Greene, H. G., Lee, V. H. K., McCulloch, D. S., and Brabb, E. E., 1973,. Faults and earthquakes in the Monterey Bay region, California: U.S. Geol. Survey Misc. Field Study M.F. -518, 14 p.

Hall, C. A., Jr., 1975, San Simeon-Hosgri fault system, coastal California: economic and environmental implications:

Science, v. 190, p. 1291-1294.

Hamilton, D. H., and Willingham, C. R., 1977, Hosgri fault zone', structure,. amount of displacement, and relationship to structures of the western Tranverse ranges: Geol:

Soc. America Abs. with programs, v. 9, no. 4, p. 429.

Kovach, R. L., and Nur; Amos (Eds.), 1973, Proceedings of the conference on tee t.onic problems of the San Andreas fault system: Stanford Univ. Pub"- Geo'L. Sci., v. 11, 494 p.

HcCulloch, D. S., Clarke,'. H., Jr, Fic.ld, H. E., Scot t, E. W.,

F-6

'l ~

~ l ~ ~

~ '7 W

and Utter, P. H., 1977, A summary report on the regional geology, petroleum potential, and environmental geology in the area of proposed'ease sale '53-A, central and northern California outer continental shelf, part A, 39 p.

Silver, E. A., 1974, Structural interpretation from free-air gravity on the California continental margin, 35 to 40 N:

Geol. Soc. America Abs. with programs, v. 6, no. 3, p. 253.

Weber, G. E., and Lajoie, K. R., 1977, Late'Pleistocene and Holocene tectonics of the San Gregorio fault zone between e

Moss Beach and Point Ano Nuevo, San Mateo County, Cali,-

fornia: Geol. Soc. America Abs. with programs, v. 9, no., 4, p. 524.

~

Hoodson, N. B., III, 1973, A bottom gravity survey- of the continental shelf between Point Lobos and Point Sur, California: Thesis, Naval Postgraduate School, 112 p.

1 ~

Figure Captions Figure 1. Hap of central California coast showing geographic locations and faults cited in text and location of Figure '2.

Figure 2. Detailed aeromagnetic map of central California coast between Point Sur and San Simeon. Flight lines 4

had 1 mile spacing, flown normal to the coast.

F-8

~ ~

~ ~

125 I21 !20

+

"" l'...

.0~ '00",~:..

~ 0 Son Francisco' 8

0~ pC a

Monterey.. "~

0 Pt. Sur X,. o Cg

~0 OC. 00 Cape Son Martin~"'.:.:,

San Simeon '-:. ~q

~

O -" ~

~:

Oy~

P )

~

Figure 2,

,Santa Pf Sot "MarIa

Basin Pl. Argualla "'::.:,~

.'. Tra nsverse Rong

""::.:,,Santa,:,

es Pi j' F-9

35'30'6u Mori h

( >w C'o,

'.t> C'g I ~

rcun

'*H,~ r'u) ~mo o 5Q

~

1S Serrc E>>

<o Og ccc C

pc<

I~ gyes'0 Kosori fc "lt 0 lo 20 p~ Io Xm Conlour tnltrvol 50 nT

-2 means 200 nT

~III>>CIIV>> liiilllIs iul ar>:Illuollc(I iul ce>>tral >>tr;ind of the S:in Andrca>> fault Ga7(7~10-J t(7.'>t of thc inodcrn San Ainlic:is fault. thc I'ilaicito>> fiult Abstract. 7%<< Sea( Circ@or(O-II(>.'ll!rif(nil( (r<<n(l Is a ('n(po(i('n( of fl(('an vIM(If<<as thus i>> thc local >>tructurd boundary l>c-fa((I( sys(e(n un >a%i<% (l(ere nn(l'n(v('>een <<lnn(( ILS Iilun(((mrs of pos(-I'arlv tsvccn I ranciscan Complex on the north-

. hlioeene rigla-la(( r<<l s(ril e slip. Ifs<<. rig%( .clip on (I(e San r'hodr<<as <<n(l San Gre- east:ind granitic basement on thc south-gurio-Ilosgri fanl(s <<t roan(s for n(os( of (l(e niui'ennva l>e(>veen (I(( I'<((ific'ani wc>>t. This prc-Slin Grcgorio f:uilt may I>,'or(II An(eric<<a pla(es .since n(i(I-hliueene (in(<<. Irnr(I(ern(ore. (IN'M(gnila(le of bc nn'sct to the north a>>';in int'err<<d>>truc-rigl(( slip on a P((leog('ne pro(a-$ <<n Anclreas Jin(l( i<<Jc'rrecl fr>nn (I(i pris('n( elis. tural contact scpar;iting thc north-(riha(ion of grani(i<< l>ase(nen( is r((la('ed ('ansi(l( rallly u%en A><<ug(n<<-R<<e(n( San ernmost granitic basement outcrops at g(i rigl(( .clip is (al'en in(o <<ceunn(. 'regoriu-II<>cveral wcll- Tertiary Gualala b;(sin ivcst of the San parallels the central California coast dclincd ni;Ijor falilts>>cern>> Iinlikcly. Andrcas fault (/0).

from its inter'ection svith thc San An- ifour evidence f'r right slip on Fur>>'hcrmore,

2) I'O'In( Reves sec(ion-Den Lun(on(I dreas fault nor thsvcst of S;m Francisco to thc fault trend is valid, throughgoing hloan(ain sec(iun offs<<( (x's in Fig. I).

south of Point Sal (Fig. I). In this rcport continuity of thc, fault zone is required. Distinctive Tertiary sections, including we prcscnt on-land gco!Ogic cviJcncc for Thc evidence for right slip consists of unconformity-bound p;lcl'ages ot I'i(lco-about I IS km of ri ht-lateral strike slip scvcn pairs ol'tl'>>et geologic fcl(turcs cenc, middle Miocene, and upper 5(io-on this complex fault zone. On-land and (Fig>>. I and 2). Yonc of thc>>c are indi- ccnc-Pliocene age. as well as com-offsliore segments of the fault trend arc vidually unequivocal. hut t:(ken togctlier parable granitic basement. occur at Point well defined by geologic mapping and they present a compelling argument. Rcycs and Bcn Lomond Mountain (II-marine surveys (I-I). Conn'ecting links Linear geologic and palcogcographic fea- I3).

remain controversial, however. where tures forming piercing points on t'liult 3) Pigeon Point Fora(a(ion-San(a Lu-inferred through shallow water in coastal planes are the mosi sensitive indicators cia Cre(ac<<o((s uJlset pair (A. s in Fig. I ).

zones where acoustic protiling data arc of strike slip (S). Certain of the oil'sct Upper Cretaceous deep-sca fan deposits absent or ambiguous (5-7). Ncverthc- pairs listed bc!oiv arc lin ar features. but of thc Pigeon Point Formation (!4, /5) unfortun:itcly nunc are tightly con- and an associated Cretaceous basin m;ir-strained. Conscqucntly, we show prob- gin (6) are probably ofl'sei from similar ablc offset ranges. Thc common denomi- fcaturcs in the Santa Lucia Range (6). In nator of I IS km (Fig. 2) is our estimate of addition. preliminary studies sucgest 80 ~

right slip on the San Gregorio-Hosgri that Oligo-I>liocene shallow- to deep-ma-fault trend. rine facies overlying the Pigeon Point GUAI.ALA KM Details ot'he offset geologic features Formation (l6) may have offset equiva-.

BASIN are prescntcd clscsvhcrc (5, 6), but in lents in thc Santa Lucia Range (5).

0 suminary they include thc I'ollowing. 4) OJfse( uf ogsl(ore ravi(v ridge I) 7%e 8udega-Gaalala f(n(l(-Pilar- (Fig. I). Silver (17) proposed that a linear BOOEGA NEAO ci(os f(n(l( oJJse( pair (asterisks in Fig. I). gravity feature offshore from Ano Nuevo PT. REYES SFB l35 05 I

I Pl SAN PEORO I I POINT REYES I PIGEON POINT A>70 MUEvo-PESCAOERO BEN LOMOMO SANTA LUCIA l25 SUR OFFSET PIGEON PT.

Fhi

$ )

(LARCITOS OFFSET OFFSET tsILVERI AN0 NUEvo PT.q FAULT BEN L'OMOMO ((7 115 KM COMMON OFFSET AT N. I- l(5 td Ae POI(IT SUR-CAMQRIA cC OFFsET IL lo5 GUA I.*LA i>>

oo PIL A AC ITOS D OFFSET SAM SIMEOM-SALIMIAM/

FRANCISCAN~ S CC 0 D I- PARTIAL OFFSET POINT SAL X OFFSET CONTACT ~

c>

95 OF INALLI BIG SUR

>>> MiOCENE SAN SIMEON O

~ I f'(MBA>h 80(7CGh IOO KM 200 KM ii 300 KM WI>

IICnO 8EACM r>>5+ CL<<'J I.ATERAI pos!TloNS or- oFFsET MlopolNTS PT. SAg ALONG SAN GREGORIO- I.IOSGRI FAULT Fig. I ttcf(). S I:>(> uf Bcutnuie fC:>lu(cs Ull'ic( in a right h>(crit >>CI>iC along ihc sh>n Grc('<>(h>-

II(>iI:(iIhi>li I(CIKI. Scc teal fa>'(liicuii>h>>I. I(ig. 2 triuhlh O(l'sct range clni(t f>>r SI>KI'col<<l I>il'>>ct I>>. iis ih>>>v(I in I>ig..l I>(I>I di>>c<>c>I in Ihc text.

St:II'.I(L'll, VOI.. IVV. I.l JANUARY 1>77>I (Kl'l(>.t(U75(7KAI(I 1 I>(795(>I).5(VII C>>Py>ighi C IV(K hhhB G-1

~ ~

~ 4 P'P MI OCENE OL CENE pALEO. Ct(ETACEOuq PRC SCNT >00 KM NQRIWRN IIHT tY SALON diSCNCNT PACIFIC N. AMERICAN PLATES (RTNATCR d NDLNRR> ISTS)

SC TOO I

w~ GOO

~

~

ill+r

~ ~ ~ ~ > ~

X MOVEMENT ON PROTO SAN ANDREAS o tI w OTHER FAULTS MOVEMENT (MAX) 500 DISREGARDING POTEtitlAL CUMULATIVE SAN GREGCRO IrIN 9

C$

400 DISPLACEMENT SAN ANDNEAS SAN GREGORIO n ill, SAtt ANOREAS FAULT JI PROTO-SAN ANDREAS SAN GREGORIO MOVEMENT IM'X )

O ACT>VIT Y CONSIDERING r SAN GREGORIO FA>f~T X

O nVl I) NCN TNCAN L~ DF SRVNMN A QRSCNCNT, FSS>~.hG hLACNC SAN AXSRCAS leJVCNCNT 10 00 Co 10 00 L<N. AGE (MYBP)

C I I

h0>&CRN VwT Dr SRLR><AN SCN AhCRCAS d $ AN ~~

SRSCNCMT R(STC NS NCOXIC Fig. 3 (left). Northern limit Of'Salinian block after restoration of Ncogcne right slip on the O

N ltQVClcCNT San AAdrcas fault alone (A) or on thc San Andrcas fault plus the San Grcgorio.HOsgri n fault trend (0). The remaining o(Tsct of gnnitic b:iscmcni noi accoun(ed for by Neogcae

1 T' right slip may be 0 measure nf right slip on 0 pro>o-San Andreas f:iu(1. Fig. 4 (Tight).

/TTIPOLC TIN>0 SAN AICACAS DTTSC'I (Curve A) Time-Of)set curve ((2) mndi(lcd tn Show the e(feet of San Ctcgorio-Hi>sgi I right slip. (Curve 0) Relative motion of the Paci(ic and North American p(ates (33). See L LI>OT FRQQASLC & text for discussion.

SCITIAN OASC+CNT I

Point is the offset expression of thc con- slice incorporated in the f'ault zone at an ration fails to consider the extension of tact between Franciscan rocks and gra- intermediate distance. Salinian basement by! 15 km of San Gre-nitic basement of the. Salinian block in 7) San Sinteon opltiolite-Point Srtl gorio-Elosgri right slip north of its inter-the Santa Lucia Range. oyltiolite offset pair (double umlerlining section with thc San Andreas I'ault (22. p.

5) Point Snr Francisran-Carnhria

~

in Fig. I). H ill (22) reported the probable f293)r Thc restoration of this additional Pines slab nfJset pair (underlining in Fig. offset of a ihfesozoic ophiolitc and an I I5 km of'Neogene to Recent right slip to I). The Fr~nciscan subduction complex overlying "Per(fary sequence from Point position 8 (Fig. 3) reduces by one-third of the central California coast is general- Sal to thc San Simeon area along the or perhaps two-thirds the apparent right-ly a potassium feldspar-free mctascdi- Hosgri scgmcnt of thc fault trend. slip of)set of the northern limit of the Sa-mentary sequence (IS, -l9). Exceptions Displaccmcnt of the Point Sal-S;m linian block by the supposed proto-San to this gcneraliza(ion arc structural Simeon ophiolitc association along the Andreas fault. Furthcrmorc. in thc un-blocks of potassium feldspar-bearing Hoscri scgmcnt occurred 5 to l3 million likely event that the limit of Sicrran base-graywacke-shale at Point Sur and Cam- years ago (22). Other of)'sct indicators ment actually lies to the not th in the sub-bria (IS, /9). These tivo blocks:ipparcnt- demonstrate post-carly Miocene and sud;Icc (30), And if Bodcga f lead is near Iy have been offset by San Gregorio- probable post-middle Miocene right slip. the northern limit of Salinian granitic Hosgri right slip. Holoccnc movcmcnt is documented basement. then a proto-San Andreas

6) Point Sar Itliaeene sarttlstone- for onland and oA'shore fault scgmcnts fault is prccludcd along the modern San Frarteisettrt sttnree terrrtne <>/set pair. (2~) Andre:>s pathway in central California.

hfiocenc s:indstonc occupies u sn>nll Granitic b:iscmcnt of'hc S:ilinian In any cvcnt, thc proto-San Andreas fitful( sli<<c ivithin the Sur fault zone seg- block west of (lie San Andre:is fault is fault app;ircntly Lvas not a transform ment of thc San Grcgorio-flosgri fault ollsct by >I A>inii>>i>11> of 5 lt) kn>. biiscd on f;iult:in:ilogous to thc modern San An-trend ne;ir Point Sur (5, 2tI). Dcspi(c the nor(hcrnmost granitic cxposurc>> at Bo- dre:is I'aiilt system. Instc:>d. proto-San Imn>cifliltc pl ox>A>lty ol I'.r;lni(ic b>I!ic deg:> Head (Itig. I). If granitic baden>cnt Andre;is f:iulting may have been thc geo-nlcnt cxpi>hcd iA hliocct>c (talc (5). (hc extends o(l'shore to I'oint Aren:i (2 I). thc logic rcsohttion of oblique subduction s;>Add(one h:lh 'till cxcl>>SILL'ly I'rilllc>si:all maximun> oil'sct i>> 600 km (Itig. 3). Rcs- along thc central Californi:i coast in ciirly provenance (5). At lc;ih( 60 ktn of right torition of'vcll.documcntcd post-Iiv- Tcr(iary time ((I ).

slip i>> required to proviilc an adequate ccnc San Andre;is right slip ol'05 kin Righ( Slip of'hc S;m Andrcas fault is I'ranciscaii source tcrranc. 'I'hc ol)'sct (24-?6) brings thc>>orthcrn litnit of co ave Alen(ly iflhpkIycif;I',I;I Iln>L"ills placcn>cnt plot on curve A in I'ig. 0 (.'.).

S:ili-'i:in cannot cxcccd l05 kn>. hoivcvcr, bc- b;iscmcnt h:ick to position A in Irig.

ci>u<c th>> silllds(ot>c I'l. ks vole>it>lc cli>s(s 3. Tl>c dill'Lrcncc bctivccn position A Thc ilottcd n>1>dili<<;i(ion nl'curve A prior typic;il of htioc<<nc si>>>>(Stot>cs near (Itig. 3);inil the no) tl>ivcst liit>it of Sicr- to 60 Inillion yc:Ir>> ago shoivs the c(l'Lc(

('>mbri:> ( I ). Tlic Ii>L'k ill ovLI'liip of riln lu>Ken>cut h;Is bccn ttlkcn;Is;I n>i'.,'I ~ of disrcg:>riling S;in Greg>irio-I lohgri LII)hct bc('ivccli Ihc I i'I>At Sul'i>oct!Ac )dirc ol'rc-I occnc "proto-8:>I> Aii- rigl>t Slip in proto-S:>I) Anilrc:ih f:Iult in-

) inifs(L>nc anil otl>cr otl'hL I p:iirs (I'ig. 2) ilrc:is".right slip (27. '8). ()Ilier rLI(ioi>al tcrprc(:itious. Curve ll in Itig. I shi>>L>

LILTCS t>O( LIL'lL"it (hc ollhCI Ill'i',lllni;AI,bc cviilcncc pk>cch (l>is ilcl'orni:>(ion in I';I~ Ihc I eh>(lvi: lnovL'AIL'}ltlic(ivccn (lie I,i L;iilsc (hi; Miocct>c tai>llifh(oi>L'h ln a Iilul( lciiccnc titnc (5. 29). I loivcvcr. thc ILVA(o. I'>Ill ilail Ho> (h Anil,>'lean pkl(cs (I )

SCII:.NEI:.. Vot.. Iv)

G-2

i

~ ~ ~ i J, C. Clack. disc<<<<a<ion. Stanfoid t<nivccvi<y 3-d:iy period on hnlns milk. Never-SYithih the iinccrt:<inty of Ihc curves, (AOSt n<OLCIACnt lv<<tLVCCA tlic platCS l)AS (1966).

I), C. Rove. U.S. Grul. Sun.. I'rc>f. I'cip. 698 (~8, pilp!i of <ill clgcs Lliiplcly fcililcc,'cl bccn loe:ilircd;ihuig (lic S;<n Andic;i>> (1972).  %)%fit;1<NI I Lip Ll<cvc loplncnt Lvllcli I, C, Cro>>c)l. Grul. Sac; Am, Bull. 68, 993 ,nursed on I<<sin) milk.

fault proper I'vr thc lait 6 niillivn years. (1957) ~

U. R, Lowe, Ivoc. 24<h Ins. Crnl. Caner. 6. 7S ln an attempt to dc(ciminc thc caiisc Bctsvccn th;it (imc:uul thc c;irly caIio- (1972).

ccAc, A<As( of tile pl<it<< Ill<1(ioA was ills 16 J. C. C)ack a<ad F.. E. Rcahh, C<rlif. Div..<(Ines of dc;ith. tissue sections from.thc af-Grcil. Sprr. I'c p., in prese. fcctccl pops werc cx:imincd histolvgi ~

triivu(<<<l bc(LLC<<n thc S;<n Amlrcas:uid 17 E. A. Silver. (irc>I. Sc>e. Ani. Ahssr. P<c>gsccrn c 6, San G<'cgorio-Ilvigri f;iult trends. Ti<us 253 (1974). cally. Thin sections of skin. lung. liver.

W, Giihcc<. Ca'<il. Sor. An<. Bull. 84, 33)7 stomach. bone. and muscle werc pre-thc prcscnt extcniion of granitic bi<ce- I)973).

. J. ) (su, C<r!i% Dias .Ltfnrs Crul. Sprr. Rc p. JS pared fron) ((-d;<y-old pup>> nursed on ment of thc S;ilinian bio;k in I:irgc part is (1969).

expl'<incd by right slip on f:iults of thc v0 P. D. Track. Bus(. Drp. Groi. Uni '. Culif. )3. Isnlns milk. The sections were st;iined

) 33 (1926) wi(h hcmatvxylin and cvsin and examined Ncogenc Sin Andre:is (nuit iyitem, as C, A. Hall. Jr.. U.S. <7ruf. Srrcv..<fisc. Field suggcstccl hy Johnson and Worn<<:rk (34). Sr<cd.,<fup .LII'L'9 ((974). under tlic light microscope. Only thc 21 , Srirnc'r 198. )29( ()975). skin appc;ircd abnnrnial, displaying. fvcal S. A. QRAHA>ct 23 F. A, Silver. J. R. Cue<ay. A. K. Ca>per. in Frplns csfios< Drparlsnrn(, 11'c stern G (,gir Gui Ir s <I Ivnrshr n Cora< Rarer.. ;iciltc clef ill;ltltis, gcllc.'I",ll Ulldcfclcvclop Pains Rrycs Rrgsi>n. Crrir)i>micr. J. Il. I.ipps;ind Region. Chevron U. <.e'L. Inc"a, F,. h(. h)oores. Fdc. (Geological Sa>eic<)i Savca-ment. and I'olliclc atrophv. FL<r(hcrmvrc, men<o. Calif,. 19 I), vo(. I. pp. I Ii<. thc str itum gfanulosum w'is signific;intly San Fs'csssciscu. Cc<1%rssics S)4I /9

~

W. R. Uickincon. D. S. Cowan, R. A. S<<h>>cick-

<<Y. I(.. DICKIHso~ cc<.Anr. Ass<>'. Pc's. ( r i. Bn<S. So. 3 c(l91 k thickened and the number of hair sh;if(s 15 V. h(a<<hews. I(t. i)ii,f. 60. 2128 (1916). marl'cdly reduced. All other organs ap-DCp<<fin< ms Of GC'OIOJLV. SICSS<fs)rcl 16 T. H. Hi)scn and h(. )I. Link. in I'ir<c<ieriir Univcfsily, Sf<<<<ford. California S)4305 Svuipusiun<. D. W. Lvcaver. G. )In<no>lay. *. pearccf nor<nal. though undersized. and Ti(><a>n, Eds. (So ie<y of Economic Pa<<<on<o)-

ogas<s and htincca)aig<c<s. Tulsa. )9151. p. 367.

no cvidcnce of infection, allergy. or in-References and!Co<es '>7 J. Suppe. Crul. S<>ai Acn. Bull. Sl, 3253 (I'9<0). complete digestion of milk was ob-28 R. W. Kic<)cr. Z. F.. pe<<<<man, D. C. Ro>>. D. sc<'veil.

I. A. K. Cooper. U.S. Crul. Su<v. Oprn Filr Rr p. Go<< fcicd, Ssanfurd Uma. Pabl. Grot. Sci. S. 339 I 901 ((973). p. 65. ((973). Histological observations ivere also

2. G. E. 'Wchec. Geol. Soc. Am. Ahssr. Programs 19 For csamp(e. scc S. A. Graham. Iv'ra<<mr Svrn-

9. 524 (1977). posiuni.*. E. Fri<vche. H. Tcc Bes<. Jr.. W. LV. made of mammary glands ot'n)los d;ims

3. H. G. Gc cne. LV. H. Lee. D. S. 8(cculioC. E. Wocn:<cd< Eds. <So<<ia<y of Economic Pal<<un-

~

whose pups were'close to death. In gen-E. Bmhb. U.S. GrnL Sun..'<fisc. Field Scud. co)ogii<s and ~1(nccatogis<s. Tu)sa. 1976). p.

hfnp <IF;<I8 11973) 125. eral, thcsc glands appeared less active

4. H. C. LVagncr. U.S. Grol. Srrni Open Filr Rrp. 30 Sec ihc du<<cd linc in Fig. 3. and smaller than (hose of normal 8/6 (1974). 31 P. J. Coney. Grus. Sor. Am. Sprr. Pup.. in S: S. *. Ciiaham. diss<<<<a<ion. S<anfocd Univccsi<y cecce mice. Moreover. we observed that Is<<iso (1976),'p. 5)0. 32 , Iodificd from chc cucves of Diekinconrc al. 124)

6. and W. R. Dickincon. Calif Div..ifinrs and Hclven and Link <26) in ac<<ocd.ance wi<)i a dams frequently yield less milk.

Gros. Si>rr. Rrp., in pccss. htiocenc Plio cne boundary near 5 million ye.icv Tal'en together. these symptoms are

7. E. A. Silver. Ga ul. Snc'. A in. Ah<sr. Progranis 9, ago. (roc a de<ail<<d div<<ussion scc Graham <5<.

500 (1917). 33 T. A<wa<cr and P. 81o<nar. Ss<<nlurd Univ.,Pub(. similar to those described by l<Iutch and

8. J. C. Cro>>eil. Gros. Soc. A n. Sprr. Pnp. ll Grus, Sri. 13. 136 (1973). Hurley (3) in rat pups nursed on dami re.

(196 ). p. 61. I, D. Johnson an 3 LV. <Ho<mack. Grolngy 2. I I

9. for ecamp(e. sec T. H: Ni(ven and T. R. Simon(. ((914). ceiving a postgestational zinc-free dict.

Jr.,J. Rcs. U.S. Grnl. $ <<n. l. 439 <)913). 35 Our ccveaceh was supponed in part by the Earth (0. C. ht. LVcm>>ocih. Ssunfi>icl Univ. Pabs. Geol. Science Sec<ion. National Science Founda<ion Thi>> dict leads to a so percent decrease Srf. I (. (30 ()968). (gian< UES 1=01728). in the zinc content of the milk by day IS 1(. A. J. Galloway, Calif. Div..<finrs GroL Bull.

202 ((977). 23 htay 1977; revised 22 Augusi 1977 of lactation, with only minimal ctfects on the other constituents. As a result. nurs-ing pups a'e severely depleted of plasma zinc. 1 Lvo-thirds of such animals die a<Hi all exhibit retarded grow(h an'd severe Zinc Deficiency in i<<furine IXIilkUndcrIics dermatitis. Nloreovcr. total milk produc-Expression of the LeIIIal (7<1'ilI'IIII)iver((t:((ion tion was reduced hy 50 pcrccnt in thc zinc-dcficicnt dams.

Abstmct. Tlsr inahilisy c>f nursing pops Io sorvivr an sssiII'f nss'cc I<os<so-i'gosss for Bcc;<L<se of the similarity of symptoms Ihe rc'ccr rivr'nuslali<<n. Icth il milk (Im).is ccsrrrlalrd i<<ills a rrclocfian in -issc levels of between thc dietary-induced zinc dcfi-boll< ss<ilI'ncl pop carcass. rlcln<inislrasiou of -ini's pnps ssssrsing on Imlm.cl<<nss cicncy and the lrflusl <<sill'yndrome, we rrdssccs Iln'lisrrvc'cl snorsalily <<ncl ssusrbsclilv. II is saggc'sfrcl lhnl Im <<l(crs -inc compared thc concentrations of zinc in lransporl freon nsafc rsusl l>lci<icl scs sssilI; <<ncl slscss ii.r ssssclynusy proviclc'srfssl infarnsa- c the milk of Inihn and normal mice. As lion for unclrrssanding slsc'are'susnass disease, cscrridcrn<afisis rnlcropashic'<<. shown in Table I, the zinc content of thc mill'l'utant mice is reduced 34 per-A rcccssivc mutation. designated le- pups pcriiit at AII i(ages of lactation (2). cent from that of normal B/6 mi<<c. This (lail nsill'lns). Lv:<8 diicovcrcd a<nong a<Ye, h;<vc evnfircncd tlmt ncvvborns fv>>- dill'crcncc is scen thrvugliout lactation niigc of thc CS"sIIL'6J (l)I6) striin (I). tcrccl on lnslns dan<8 'it mid-lact;itinn or and is rc(lcctcd in thc whole body zinc Pups nuried on i<<ilia d:iin>> exhibit stunt- I;i(c hie(:<(ion;irc ai s<<vc<'c'.IV <itl'a.'cled iis COnC<<ntratiunS Of S-clay-VI<I SOCkling ani-cLI groi'vill,;<elite <le<'ill;lli'Ils, alopcci;1 ~ (I<use All<'i<<LI(fL'<1<1 (lie beg<An<A<: of I;<c(il mals. Ilowcver, Lvc fvunil nv such deti-and Llc:ith prior to Lvcanin. Since normal lion, In;<clclition, Lvc have foun<I;1 Llif- cicncy in either the phiinia ol'lactating BI6 pupi (I.nsl.ns) dic rvhcn nuricd on fcfcACC ili husccp1<l'ail<tv tv thc c(lects vf Is<ills< LI,'lillsi Llf ln tlic c;ifc,'<sacs ot:<<lilt(

In<los inilk, (lie clcfcct rciial<<i in(hc milk. lnslsn <<<ilk cvith rcip<<ct tv thc <)'.c Is<siss< fcn<1<lcs. Sill<.'C ><chil( is<siss< Ic:A1<<lci I lvlcoic<', linln< pi<ps dcvclc'>p tlol'<ll;illy >i(owl<of<i pl<ps;<lc.'f<'cvcfillsly OI'i<pi.

exhibit norm;il conccntr;i(iong OI'ot;il if fiiitCr-nuriC<l Vn;i AO<in:il Clam. (.>C- co<An<i(teil to if<<1<th:1('Icf 3 d;<yi on In<los hvdy zinc. it:ippc:<rs (hat the mut:iticiii nctic 'in:ilyici inalic;ite tliat lns ii loc:i(cd A<ilk. cvcii wh<<ii siihscquvntly tfani- involves re<inc<<LI trini(ort o('zinc from Vll L'hi'La<llviO<11<< (<lid ill l(si ),6 \:el<(i (L<<ccl I<<:i iio<<>>:il .I'cni. ()hler piipi, on pi'<in<<: I<1 <liilk. I hc It.'6 d:in<8 niaint:ii<1;I nlol'I'ini lio>>1(lic;igooti hs) loci<i. tli<<otlici li;iiul, Ii;iviiigniiric<l oii in<i <n;il 2<ii<< co<ieciitfatlon iu thc <<iilk tliat ii tcn I llc cllccts La( lssslsss I<Ill(i clll 1<a)who<ii niill ('r, u iccv d.iys, I'<irqucntly h<<rv i VC:< tliilcs h<1',tie<'tlilil thilt isl Ill<< plilii:li<

SCII!h<CIL YUI.. IV'S, IJ JA'St<A)tv )><78 0<)3(> g<<)ss7<LS) l)J uu<(s<>a<.5<L'0 (:opy right 0 197>8 AAAS 1st G-3

~ y

~,

4 ~

Roprinlcd from

'6 Docombor 1975, Volumo 190, pp. 1 l 294 San Simeon-Hosgri Fault Syhten), Coastal California: The San Simeon fault terminates the Arroyo dcl Oso fault, which cuts through Economic and Environmental Implications the lower part of thc 12-m terrace (l. 4).

Thc Pl<<istocenc terrace deposits within the region arc 130,000 >30,000 and 140.000 Abstract. There has been 80 l'ilomerrrs or ntore of right slip along the late I7unIernary + 20,000 years otd (5); therefore thc Ar-San Simeon-llosgri faulI sysrem of caasral California during" the last 5 Io 13 million royo del Oso fault is younger than approx-years. Parr of an oil-rich basin is Probablyogser by this fnulI system, and Iht'sysrcm may imately 130,000 years and, at least in part, be a potential ha:ard Io nearby slrucrures. thc San Simeon fault must be s(ill younger.

An epicenter (date unrceordcd) is located Comparison of stratigraphic sections ex- other unnamed canyons between Arroyo on the Arroyo dcl Oso fault and thc mag-posed on opposite sides of thc late Quater- dc los Chinos and Arroyo dc la Cruz (4). nitude of the earthquake is reported to nary San Simeon-llosgri fault system at Each canyon is marked by right lateral de- have been bctwcen 4.0 and 4.4 (6). Holden Point Sal and near San Simeon (Fig. 1) viation of 150 to 450 m: however. the fault (7) reports earthquakes of 26 October or strongly suggests large-scale lateral dis- does not juxtapose markedly dilTercnt rock 26 November 1852 and I February 1853 at placement. Thc nature and agc ol'trikc- sequences or types (Fig. 2) as docs the San San Simeon, where "houses were injured.n slip displacement along the fault system Simeon fault. However, the authenticity ol'hese early has important economic and environmen-tal implications, for it suggests the possible location of an ofTshorc extension of the oil-

'.~co producing Santa Maria basin and indicates that thc system poses u potential hazard to Cooo Soo MofloI cngincered facilities. o+

Thc San Simeon fault in coastal first named in 1974 (I), can be central'alifornia, ROSSOO Pt traced on land for a distance of approxi- oo V ROCOOI TZ mately 19 km-that is,'rom Ragged Point Pl &44oo Bloncoo I>>B4II~ ~

oo 54oooo to San Simeon Point (Fig. 2). ln the area Soo SnoOOII PI Polo Rootoo offshore from Ragged Point, Hoskins and 0eo COolno o GriAiths (2) show a 65-km northwestward oILov extension of thc San Simeon fault. Silver ,p oop (3) reports a fault with as much as 5 km of Pl f XoIo OI ~ oQ Ch dip separation in the olTshore basin south of Point Sur (that is. 80 km north of San TI Mono l OOv Simeon), whi<<h may bc thc northern exten- Cl Bog r sion of thc San Simeon fault. The San Y, Simeon fault may also extend farther south from San Simeon Point to near Point Estcro (Fig. I) in thc utTshore, as olla Vr Pl Soo LIoo postulated by others (l). Such a suggestion C) XnOIO ov Bronco Orv oo is supported by the fact that the coastline is hot oCg straight and rises abruptly from the sea. t ca Near San Simeon Point the trace of thc ;O San Sim<<on fault is concealed by late oo/

Pleistoecnc or Holocene slightly cemented 0 lO oIIloo I OI dune sand d<<posits. lt faults the 122-m Plcistoeenc terrace approximately 5 km northeast of Point Pi<<tlras Slaneas, but inputs Ponoono Pl docs not eut the 12-m terra<<<<near either Srcaker 1'oint or Ragged 1'oint.

The Arroyo Laguna fault (Fig. 2) is be- Lonooc lieved to be a relatively >ounger and morc Pl AIOOOOO recently active strand ol'he San Simeon Moo LOCOInoI fault zone. This fault is m:irk<<J by a pro-noun<<ed lin<<ar valley north of San Sim<<on Point (4), hy a 75-m fault s<<arp, and by Pt Concooloo>>>>

faulting of the 122-m Pleistocene t<<rracc. 1 Bio The fault crosses s<<v<<ral west- or south-I'ig. I. Location ul'ihc Sun Silo<<un I lutgri fault system. I)use mup ic frnui Jennings I I I) un J several west.draining canyons, including Arro>o ut her sources (I.Z. 4. u. IO. 13). in J it~ tc hypuhyxs ll plugs of the blur la Itu<<k - Islay I lillturn.

llondu. Arroyo dc lus Chinos. and three plex (I, IO, I7).

~ ss earthquake reports has been qucsti fault suggest tllat lt could hc sclsnllcall~ Thc rocks in thc I'oint Sal area have (8). active (I, IO, l2). Arpuntcnts supportin~ ccn d<<scrih<<d Ity IVoodring and aml refuting th<<possiltility of strike-slip lcttc (/4) and. morc rc<<<<ntly, tile opltiniitc llram-'as Thc San Simeon fault tcrminatcs thc O<<cani<<IVcst lluasna-Suey fault system along thc llosgri Iault have h<<cn d<<scribed hy I lopson <<r al. (I5). 'novcmcnt (Fig. I). The IVcst lluasna fault may tcr- been caret'ully r<<viewed (I); how<<vcr, new Thc old<<st rocks in that ar<<a arc those of

.ntinatc thc )idna fault (9). which in turn data present<<d herc strongly suggest that the Jurassic (~ l60 million y<<ars) ophiolit<<,

displa<<cs I'Icistoc<<nc anti late I'I<<istoccnc thc San Sitncon and }losgri faults arc part which consists of a lower part of s<<rp<<ntin-deposits (9). Thus, although mov<<ment be- of thc same syst<<m, right slip accounting itc. layer<<d ultramalic ro<<ks. and gabbro:

gan carlicr, probably bctvvccn thc late for thc distribution ol'urassic to Plio<<<<nc and an upp<<r part of diorit<<. quartz diorite, Mioccn<<and late Plio<<cnc, th<<San Sim- rocks. a dike and sill complex, and submarine pil-eon Iault must be Plcistoccnc or younger. Recent geologic mapping near San Sim- low lavas. Greenish-gray tulTa<<<<ous radio-and strands or associ tt<<d faults may bc eon (4) and thc area b<<twccn Santa Maria larian chert, overlain by Jurassic shale and even younger. and Snn Simeon (9. I3) (I'igts. I and 2) has sandstone. r<<sts on thc ophiolitc complex Thc Hosgri fault (l0), also called thc shown that remarkable similarities exist (I5). A similar sequ<<n<<c of rocks occurs East Boumlary fault or fault zone (I), ex- bctw<<en rocks west ol'he San Sim<<on north ol'S;m Simeon (I'ig. 2) between the tends southeastward from near Point fault zone, nc:tr San Simeon,.and cast of Arroyo dcl Oso and San Sim<<on Iaults, Piedras Blancas to near Point Sal, but thc I losgri fault near Point Sal (Fig. I). Ju- but thc lower part of thc complex prcscnt south of Point Sal thc continuation is not rassic ophioliti:, ovcrhtin successively by near Point Sal is appar<<ntly ahs<<nt, as arc clear (II). Seismic reliection records (I, tulTaccous radiolarian <<h<<rt and Jurassic thc submarine lavas. in thc San Simeon l0) show that there has been dip separa- shale: Oligoccnc nonmarine conglom<<rate, area.

tion, with thc west side moving down rcla- associated tutf, and distinctive landslide A Jurassic ophiolitc cast of'Ivlorro Bay tivc to thc cast side. Di}Tercntial movcmcnt deposits: and later Tertiary cherty shale (13. 16). cast of the San Simeon fault, and

'has oc<<urrcd intermittently along thc Hos- composition and histories ar<<oIT- in relatively close proximity to San Sim-ol'imilar gri fault from late Miocene to Holocene sct (Fig. 3). The horizontal slip component eon, is overlain by rcd radiolarian chert, time (I). Earthquake cpicenters along the may bc SO km or more. not thc distinctive greenish-gray tu(Taccous chert west ol'the San Simeon fault.

Thc Franciscan shale (Fig. 2) in the San XPLA N A TION Simeon area consists of'dark greenish-gray E

and brosvn weathering clay shale. The unit

~rs S essee Iosse I CQ is lithologically similar to thc l.londa For-L mation ol'ibblec (IT) south of Point Sal,

~ts TII'e', but it is not recognized in the Santa Maria stooge I.'lie'e "", Q s eeosee et ssspe OseteROO area; it is presumed to lie vvithin the SueS~ Tos', 5 fault block northeast of the San Simeon Peee Sol res OW sOo Os ee

~ ss fault.

Jurassic shale in the San Simeon area is vota ~ eo<sssosws lithologically similar to the Knoxville For-LosOO tuu mation (14) in the Santa Maria area and the Espada Formation of Dibbl<<e (/7) far-Losoo ther south. In both the Point Sal and San voodoo>>so too Simeon areas thc Jurassic shale contains PI SO>>O eRI

~ CIsesl es beds of conglomerate consisting of wcll-

~ss rounded, smooth, small. black chert peb-01 ~ Oe>>R bles.

solCOISso Cesssesee Stratigraphically above the Jurassic dodo ophiolitc-chert-shale sequ<<ncc in both the San Simeon and Point Sal areas is the Lospe Formation (Fi>>. 2), a nonmarine StsotI\Issl rock unit consisting chielly of reddish con-Rseeeles Ito glomerat<<and coarse-grained sandstone Ceesoet and tuIT overlain by grc<<nish sandstone and tulT (l4). In the Point Sal area the Lospc Formation (/4. I5) of Oligoccnc agc

+e O~ overlaps Jurassic shale and r<<sts on thc e

"o Sate .'

eo ophiolitc complex. In thc San Simeon area Ueo Lee ~ Iw

'avl.t'eeee similar stratigraphic relationships are

/esses complicat<<d by faulting (Fig. 2). Thc Oeosett Ot C a ROO. loads eeeoesese greenish saridstone is not well developed Soo Seeeoss Poese near San Simeon. In both the Point Sal ISI IS and San Sitn<<on areas thc <<onglomerate is Fig. 2. Prc.Quaternary gcotocic mup shnwinc distribution und stratigraphic relations of the Jurassic unsorted <<nd poorly stratified. Clasts ophiulitc, chert, ural sbutc scqucnw.: thc Oligocene l.o>>pc I'ormatiorn und ltluntcrcy Shale near San range in size from a fcw inches to several Simeon, California t4). This mup should bc compared with geologic maps of thc Point Sut-t.ious feet in diatnctcr and consist of rocks fromcud urea (/4, IS), where thc Luspc Formation ovcrlics the Jurassic ophiolitc uud shale. The ru<<ks in thc Sun Simcun }toint urea would have been ut least l2 knt otfshorc from Point Sul prior to movc- the ophiolitc <<ompl<<x and l<<sscr amounts mcnt along thc Sun Simeon-} losgri fault system. of Jurassic chert and shale. Novvhcrc in the H-2

Son Simeon Point Lospc I'ormation west of thc San Sin<<<on Point St)l Lion d Rot)<<et< Point fault (Fig. 2) arc th<<rc clasts ol'da<<itc < lot tet fclsitc from thc 22-million- to 26-millio<I- <Coetotd roeooteoh< year-old Morro Rock-Islay flill complex <<4llleeti rteeeoiah Tm+ (9, 13. 18), the dacitc ol'Ro<<ky Butte(T1 in V C deoOOSt Fig. 3. Pfe.Quaternary com-Fig. I), or thc Camhria I'clsitc (9. le')). Da- posite stratigraphic sections of roche 5 $< <O eOIOO

                                                                                                                                                                               'ho citc and f<<!sit<<clasts are not pr<<sent in thc rocks in the Point Sal-Lions                 oo~t<                              Loiot 4 hot oh
                                                                                                                                                       ~         ehJIVI de n Losp<<Formation in thc I'oint Sal r<<gion. llead area, Santa Barbara og~uo o os                                                                               J,o o.eie.,s' LQ o0 feohr IIIOO toil I        $ C),lc   J<< 6 )C J<'Ce flowcvcr, clasts of these rocks ar<<pr<<sent               County (14. 15). and the San Simeon Point-Ragged Point                    Jsh                      Jttoiiet  Ilott                      Jsti in the Lospe and Oligocene and lower a<ca. San Lui>>

Miocene rocks only a fcw kilometers Obispo County JotaSIK ihtel ~++ Jere C2 of San Simeon (9) and near Cambria. Thus, the inference is made that Lospc east (4).

                                                                                            ~     ~a~c>>t C0 dot aid I O                                                   dat ohd I u

~ strata west of thc S:m Simeon fault zone ducat Ohd Oosaeo I Othettdt r d<oeitt ahd ulttaehaha eOCII werc not in the Cambria area at thc ti<ne of Oiieoeho tel'NII their deposition. Clasts ol'dacitc and Cam-bria Fclsite arc present only in Pleistocene and younger deposits ivest of the San Sim-eon fault (4). dred square kilometers that have been If thc conclusion is correct. then th<<rc There are volcanic ash or tuff deposits mapped cast of the San Simeon fault and are at least three signilicant corollaries. within thc Lospe Formation at both thc northwest ol'anta Mafia (9, 13) thick I) Thc rate ol'motion b<<tween the Pa<<if-Point Sal and San Siineon localities. At black chert beds are not present. ic and North American plates. between 4.5 Point Sal the tulT occurs near the base of A small outcrop probably of Pliocene and IO million years ago. averaged 4.5 cm/ thc conglomerate and near the middle of agc has been mapped near San Simeon year accordinc to Ativater and %(ulnar thc Lospe Formation (14); north ol'an (Fig. 2) within the San Simeon fault zone. (20). Therefore, 450 km of displac<<ment Simeon it occurs above conglomcratc. Thc outcrop contains marine fossil>>: Den- would have taken place within the last IO South of Point Sal, near Lions Head. a drastcr spic bryozoa. Den<alias< spic Solen million y<<ars. This cal<<ulated amount ex-landslide occurs within the Lospc Forma- sp.. and Nuculana 1 Saccella) tapi<ria (Dull. ceeds right slip m<<asurcd along thc San tion bcloiv a prominent white tutT b<.d (14). f897). The fossils do not date the rocks Andreas fault by 150 km (21) during the South of Breaker Point (Fig. 2) a large more precisely than early Pliocene to last IO to l2 million years. Sonic of th<<rel-Oligocene hndslidc or alluvial fan also lies Holocene. The litholocy. hoivever. is sim- ative motion. 80 'km in 5 million to 13 mil-immediately beloiv tuff and other volcanic ilar to that of the Graciosa Coarsc- lion years, may have b<<cn taken up or;ib-rocks ivithin the Lospc 'Formation. flere Grained Member of the Cureaga Sand- sorbcd in the Salinia block or-as suc-clasts in the Lospc landslide are more vari- stone in thc Santa lvlaria area (14). gcsted here olTshore along thc San Sim-able in size and lithology than those in thc On the whole, strong stratigraphic and eon-Hosgri fault system. Lospe landslide south ol'oint Sal: how- lithologic similarities exist between two 2) The Santa Maria basin contains sev-cvcr, at both localities the clasts arc pre- packages of five or six lithologic units ex- eral producing oil fields (/9). A thickness dominantly scrpcntinite, cabbro. diorite, posed in the San Simeon and Point Sal of 300 m to 4 km of Cenozoic sedimentary and basaltic rocks. Thc occurrence of dis- areas. Thc diameters of thcsc relatively rocks is present offshore I'rom the San tinctive landslides or landslide. like depos- unique lithologic packagt.s arc estimated Simeon area (1-3) and would bc part of the its immediately below a tull'ed in the at not morc than 20 km each (4, 9. 13-15, Santa Ih1aria basin that has been displ Iced same form'ation at two widely separated 19). Rock sequences within a radius of 20 northward along the San Sim<<on-Ilosgri localities on opposite sides of thc San Sim- to IOO km to the east of San Simeon are fault system. Instead of simple w<<stward eon-Hoscri fault system strongly argues unlike those west ol'the San Simeon I'cult. projection ol'that part of the Santa Maria for their preslip contiguity. Comparison of the stratigraphic and basin, ivhich is currently produ<<inc <<om-In addition to thc r<<markabl<<sim- lithologic histories of the areas near Point mcrcial quantities ol'hydrocarbons. Un 80-ihritics between rock types, structural Sal and San Sim<<on (Fig. I), ar<<as that lic km northwest projection might bc morc styles. and stratigraphic relationships of on opposite sides of the San Simeon-Hos- valid. thc dio rite and dike and sill complex within gri fault system, indicates stronc cvidcncc 3) Thc late Quaternary San Sim<<on-thc ophiolitc and to thc presence of thc for right slip of 80 or morc kilomctcrs Hosgri fault system could bc a pot<<niial Lospc Formation near Point Sal and San along thc fault system since thc late Mio- hiiz.ird to any <<ngin<<cr<<d stru<<tur<< lo<<:i<cd Simeon, ther<< i>> an extraordinary resem- ccnc or cafly Plio<<<<f<c. It is iissunlcd that along thc coast I'rom San Simt.'l)n soUtli tt) blance b<<tiveen th<< lithologics of thc s<<paration is equal to or nearly <<qual to the vi<<inity of Purisima Point (I'ig. I). middle or upper part of thc Monterey thc horizontal slip compon<<nt. Th>> un- C. A. H*t.<. JR. Shale at these tivo areas. In both r<< ions <<ertainti<<s of d<<termining th<<niinimum Drpartrr<cr<t of Cieoir)gy. and east and west of the San Simeon I'iiult horizontal slip compon<<nt ar<<equal to the University of Calijirrnirr. there is thin-h<<ddcd cherty sliatc -a char- unccrtainti<<s. in onc dir<<<<tion. ol'h<< I.os rlngel<s t)N)24 acteristic of thc iblontcfcy Slialc. I lowcvcr, maxinium size ol'hc ar<<a of thc strati- ttcfcitncch and.'hutch west of thc San Simeon fault. approxi- graphic packag<<s. Thus. tli<< liorizontal slip t. Earth Ssicnic A$ioci:Itch <Palo A<to. <'Ii<i<'.h -(ic-mately km northivcst ot'an Sim<<on co<nponcnt is <<ailculatcd to hc 80 k<n or olugy of Ihc $ In<harn ( o,iii it ul<'c\ Iiui< thc <lii-

                                                                                                                     <itinlltg ii<iiililteinil'Ilini'n<.'Ii nl.lrrln Iii ( .IIII i<Ill.l, P( int (I'ig. 2). 0.3- to I-m-<hi 'k I I.
                                                                                                                                                                                    ~

morc (tliat is. Uior<< than IOO kin h<<tween III< $ ficcta I rile <clice Iii Inc I'I'it<it}'iIn Iic 'I IIII<I

                                                                                                                         <I                                               <        IS
          <<h<<rt intcrh<<ild<<d ivith diatonia<<coUs 'I'oint Sal and San Sin<<<on I'oint, minus ol'l:Ick of<he San t,uth Riinfc anil tii<cto tia$ .- re<hit< Ior Paci<i<<(eah anti I'<I~<tie('omp.in$ iii ciIahli.h ihi             ~

siltsto<ic <Ifc <<Iso I)resent. SI)U<h of I'$)int thc cstimat<<d maxiiuuin 20-LIII dia<n<<t<<r <cnuai Sir hciintis acnini <ha< iouhi a<fr<< t)iahl.i Sal, n<<ar I.ions llcail, id<<ntical lithologics of thc area ol'h<<str;itigraphi<<p;Ickiigcs at (.al$ )'till fdili'<intr t oucr t'I.ill< I'IN I. Z. tt (i. <tuiLuih anil J. It. <iri<<iihq e<ett. C<iioi. l'rr. occur (14). I II)wcvcf. In tl<$.'sever;II hi<n S:in Siin<<on;ind I',oint Sal). (Irol. htrett. <S. 3< $ t te)11) H-3

E. A. Silver. (l974) p.6 I Sa~uin Grrrl. Srrr. Short Crnrrsr C. A. Ii;rll Jr.. Geologic map of thc Iricdtas l4. tV, P. Nrrrrrdt(ng and Surv. I'mf. Pup. 222 IS. C. *. Ilupvmr. C. J. I:r

                                                                                               ~

(~ Itwmlctte. U 9. Grul. o, L'. A. I'es<<rgno. Jr.. J. Elan<<as-San Simeon region. Califutma. in ptcpr ~ M. Matttnwn. -I'tcliminary rc/Nrrt and gerrirreic ration. uide to thc Jur;rvsic ophiolitc near Point .'(al. II. II. Vceb and J. W. Valentine. Grul, Sur'. rlnt. 'outhctn California <<uast." Grul. Sar.:Iw. Car-Bull, 78. 547 ( l9/rg). dillrrun Srrt. Guldrb. Firld 7rip Plu. (March  ! 6 CaN/. Drp. It'atrr Krruur. Bull. I id 2 (1964). I 975). 7 E. S. Iloldcn. Srrrithson. Jlisr. Cullrrt. /087 l6. B, hl. Page. Grul. Sar. Anr. Bull. gl. 957 ( I972). (I 897). (7. T. W. Dibhlcc Jr.. Calif. Div..tfinrs Bull. I!0 P. Squibb. personal communication. hlr. Squibh is (I950). pata ps+ident uf thc San Luis Obispo County i(is. Ig, W. Cr. Ernst and C. A. Ilail Jr.. Grul. Sor. Anr. totica(Society. Bull. 8<. 523 (1974). C. A. I lail Jr.. Grul. Srrc. vlnr. Bull. 7)L 559 ( l 967): l9, Pacrfic Sectipn. American Asso<<iation of Petro-CoNf. Div.,tllnrs Grrrl.,tfup Shrrt (l973); U..S; leum Gcologivts, Currrlatinn Sc anion across Santa Grol. Surv. 3/irr. FirldSturl..t /up.tl F.! I I ( I')73): .')/aria Burin I: ( l 959k US. Urrrl. Surv..tffrra Firld Strrd. Jlap t/F.!Ou 20. T. Atrratcr and P. hlolnar. Stanford Univ. Pub/. (1974): D. L. Tutncr. Grrrl. Sr>c; Anr. Sprr. Pup. IJ ( l973). p. I 36. l24 (l970). p. 9I: D. L. Turner. R. C. Sutdam. C. 2I. O. F. Ilulfman. Geol. So>>. rtnr. Bull. 83. 29(3 A. Ilail. Grol. Sur. Am. rtbrtr. Curdillrrun Srrt. 2. ( I 972). I !5 (1970). 22. Public>>ation approved by the director. U.S. Geolog-IO II. C. tVagner. US. Grol. Surv. Oprn Filr Rrp. 74- ical Survey. I thank W. G. Iitnst. G. Octtcl. E. 2!2 (1974). Pampeyan. and II. Wagner for therr crrnstru<<tive C. W. Jennings. Col% Div. 3/inrs Grul. Prrlirn. comments. J. Gucnther and V. Jones drafted thc Rrp. IJ ( I 973). figures. Research supported bv thc U.S. Gcologi ~ l2. W. Gawthtop. U.S. Graf. Surv. Oprn Filr Krp. 7$ - cal Survey. the (qu<<lear RcguLnury Commission. IJs (I975I and th>> University of California Rcscar<<h Com-San Luiv Obispo region, 'Z. 13 C. A. Ilail Jr.. "GcrrIoki<<map of thc Cayucos-Grol. Surv.. rtfisr. mittee, 29 August l975: rcviscd l4 October l 975 FirtdS/ud..tlap. in press. Copyriyht831/J78 bp the Ame)scan Association for the Advancement of Science H-4

J. i iL In press, to be ublished in "San Gregorio-Hosgri Fault Z , California," edited by E.A,. Silver o W. R. Hewmark, Calif. Div. of Mines cx Geology, Soecial Ressort 137. ORXGIN AND DEVELOPMENT OF THE LO fPOC-SANTA lARIA PULL-APART BASXN AND ITS RELATION TO TElE SAN SIMEON-HOSGRX STRIKE-SLIP FAULT, WESTERN CALXFORNXA

                                .Clarence A. Elall, Jr.

Department of Earth and Space Sciences University of California

                          ~

Los Angeles, California 90024 ABSTRACT for the distribution of C ~ A model is proposed to account Cretaceous and Eocene . sedimentary rocks, and distinctive Tertiary igneous, sedimentary, and volcani clastic rocks'that lie within the Western Transverse Ranges and the Santa Maria-Lompoc region, Santa Barbara County, California. Comparisons of lithologies and stratigraphic sections tend to support the hypothesis that the Tertiary Santd Maria-Lompoc basin is a pull-apart structure that began to form about 14 m.y. ago. Following deposition of the late Tertiary sediments, the western part of the basin was displaced, since the Pliocene, nearly 80 to 95 km to the northwest along the San Simeon-Hosgri fault'one.. INTRODUCTION A speculative model is proposed to account for the distribution of Tertiary igneous, sedimentary, and volcaniclastic rocks that lie within the Santa Maria-Lompoc region, Santa Barbara County, California. Geologic mapping, analyses of core holes .and well data (Hall, 1977), and preliminary field investigations southeast of Santa Maria, California suggest the presence of the Santa Maria River fault (Fig. 1) and that the Santa Maria-River-Foxen Canyon-Little Pine fault zone. (Fig. 1) may extend more than 100 km to the southeast. Work on thi fault zone has brought to light some provoca-tive geologic relationships which provide support for several structural models

for the development of Tertiary marine basins along the coast of California and relatively recent movement on a major fault system in the region. In addition, this work suggest's the presence of the inferred Lompoc-Solvang fault, which in large measure appears to represent the northwestern structural margin of the Transverse Ranges. STRATIGRAPHY Immediately northeast of the'anta Maria River fault (Hall, 1977; and Fig. 1), i.e., within 3 'to 4 km of the fault, the following Mesozoic and Tertiary rock units are present: (1) Franciscan melange (thickness unknown), (2) Unnamed Cretaceous rocks (more than 457. m), (3) Sespe-Lospe formations (152 m), (4) Vaqueros-Rincon formations (304 m),'5) Obispo Formation (335-.609 m), (6) Point Sal or Lower Monterey Formation (304 m), and (7) Monterey Formation (1066 m) (Table 1). The Sespe-Lospe formations are not known to be present within 3 to 4 im southwest of the Santa Maria River fault. Southwest of the Santa Maria R'ver fault, i.e., within a distance of 9.7 km of the fault, or in the case of the Sespe-Lospe, more than 4 km from the fault, the following rock units are present: (1) Franciscan melange (thickness unknown), (2) Sespe-Lospe formations (609 m), (3) Point Sal Formation (228 m), (4) Monterey Formation (629 m), (5) Sisquoc Formation (498 m), (6) Foxen Mudstone (88 m), .(7) Careaga Sandstone (43 m) (Woodring and Bramlette, 1950; and Fig. 2). Although the stratigraphy northeast and southwest of the Santa Maria River fault is markedly different, i.e., Cretaceous rocks, Vaqueros Sandstone, and iHncon Shale, and in part Sespe-Lospe are absent in the Santa Maria Valley area, the most significant difference is the absence of between 335 m and 610 m of volcanic rocks, including volcanic ash (Obispo Formation) within a distance of 35 to 40 km southwest of the fault, but the presence of the Tranquillon

volcaniclastic rocks, of the same age as the Obispo Foxmation, on the southwest margin of the basin more than 35 km to the south (Fig. 1). TERTIARY BASIN HISTORY At least three models can be proposed to account for the absence of rock units with distinctive lithologies, namely, the Vaqueros, Rincon, il and Obispo formations southwest of the Santa Maria River fault: (1) strike-slip movement of tens of kilometers along the fault bringing into juxtaposition markedly dif-ferent stratigraphic sections; (2) the area between the Santa Ynez Mountains and the Santa Maria River was a topographic high during the time when the Vaqueros and Rincon ormations were being deposited elsewhere in the region, and the Obispo-Tranquillon volcan'c rocks have been eroded from this region; or (3) the development oz a'ull-apart basin (the" formation of pull-apart basins is dis-cussed by Crowell, 1974) zollowing the deposition of the Vaqueros, Rincon, and Obispo-Tranquillon zormat'ons. The first hypothesis, namely large post-Monterey Formation or Obispo-Tranquillon volcanic rock strike-slip along the Santa Maria River fault, is difzicult to test. If right-slip along the fault did occur,

                                                            't the Obispo volcanic rocks formerly near the intersection of the Santa Maria River and Santa Maria   Mesa   faults (Fig. 1) would have been moved northwestward and 'now would be  buried beneath the Pismo sand dunes ox        lie below San Luis Bay in the Pacific Ocean'(Jennings,      1959;  Hall and Corbato, 1967;     Hall; 1973)-

The second hypothesis, that is, prior to the deposition of the Monterey shales the area between the Santa Ynez Mountains and the Santa Maria River fault was a topographic high, or the Vaqueros, Rincon and Obispo formations were deposited and subsequently eroded away, can ezplain the distribution of the Tertiary rocks. However, the absence of Cretaceous rocks in this area, but their presence bounding t'e area (Fig. 1) and the presence .of Eocene rocks north

                                                                                                   ~ ~

4 i and south of the Little Pine fault,'near the Lorna Alta fault '(Fig. 1), but their absence in the subsurface in the vicinity of Santa Ynez, approximately 15 km to the west of the Lorna Alta fault, and elsewhere in the basin between the Santa Haria River-Foxen Canyon fault (Fig. 1), is difficult to explain by this hypo-thesis, unless one assumes that the Cretaceous or Eocene rocks were also eroded I completely off of a Franciscan topographic high. Also, subsurface data do not , provide evidence of uneroded remnants of these units. Furthermore, if the wedge-shaped Santa Haria basin was a high during or following, for example, the time of deposition of the Vaqueros and. Rincon in or surrounding the region and the deposition of the Obispo volcanic ash in a marine environment within the basin, it would require an unusual history for the basin. The events would have been: (a) the deposition of the non-marine Sespe-Lospe formations, (b) the deposition of the shallow-water marine Vaqueros Sandstone followed by the deep-water deposited ~~ con Shale either surrounding the basin or within the basin, (c) the deposition of the Obispo tuff within a marine, basin, (3) the 'eep-water basin would have been uplifted,'ith the Vaqueros, Rincon, and Obispo eroded away, and (3) the" the area would have been down-dropped almost simul-taneously w'th the erosion of the Obispo Formation so that the deep-water Point Sal or Lower Monterey and Monterey Formations could be deposited in a deepening basin. Note that the base of the Monterey Formation is between 10,000 and 15,000 feet (3048 to 4572 m),below sea level (Fig. 1). Thus a wedge-shaped high would

              'I have to   persist from Oligocene to Miocene while the area surrounding'he high would be subsiding, and then the high-standing land mass would have to subside rapidly in theHiocene       and Pliocene     to allow deep-water Point Sal, Monterey        and Pliocene sediments to cover the supposed high-standing land mass.

Comparisons of lithologies and stratigraphic sections (Table 1) tend to support the third model for the development of a.Santa Maria-Lompoc pull-apart

basin, although detailed stratigraphic and lithologic studies are yet to be made. In the western Santa Ynez Mountains the stratigraphic section is unlike that north of Santa Ynez Valley (Lompoc, Buellton, Santa Ynez,, Fig. 1),.but it . agrees relatively closely with the stratigraphic section north of the Santa Maria River-Little Pine fault system nearly 45 km to. the north (near Santa Maria, Fig. 1, Table 1). The stratigraphic section in the western Santa Ynez Mountains (east of Point Arguello, Fig. 1) includes: (1) Franciscan melange and Honda Formation (457 m), (2) Cretaceous rocks (2743 m), (3) Oligocene and Eocene rocks (1981 m), (4) Sespe-Lospe formation (91 m), (5) Vaqueros-Rincon units (213 m), (6) Tranquillon Volcanics (365 m), and (7) Monterey Formation (914 m). Tne Tranquillon Volcanics are the same age as the Obispo Formation (Tranquillon Volcanics: 17 + 1.2 (basalt), 16.8 + .5 (tuff), 16.1 i ..6 (tuff) m.y.; Obispo Formation: 15.3 + .9, 16.3 + .5, 15.4 + .5, 15.3 + .5, 16.5 + .8 m.y.; Turner, 1970). This sequence of rocks does not correspond exactly with tha on the north s"de of the basin, namely north of the Santa Maria River fault, and a reconstruction of the Tertiary geologic history of the region prior to pulling apart of the basin is required to understand why exact correlations cannot be made. A generalized possible Tertiary history of the development of the Santa Maria-Lompoc basin could be as follows. Figure 2a shows a generalized paleo-geologic map after the deposition of the Gaviota Formation of Oligocene age and older rock units (Cretaceous, K; Eocene, E). Before deposition of the non-marine Sespe Formation there could have been strike-slip along the inferred fault, as shown in Figure 2b (diamonds). Later, oblique rifting along this fault (post Obispo, post Fig. 2d time) would account for the development of the . Santa Maria-Lompoc basin. The inferred fault (diamonds) is called the Lompoc-Solvang fault (Fig. 1). Its inferred presence is supported by the fact that

north of its approximate location the stratigraphy (known from exploratory oil wells) is markedly different from that south of the inferred fault. Figure 2c depicts a generali.zed paleogeologic map before the deposition of the Monterey Formation. Sespe-Alegria formations (in part Lospe Formation), Vaqueros Sand-stone, Rincon Shale, and Obispo-Tranquillon volcanic rocks unconformably over-lie the Franciscan rocks (F), Cretaceous rocks (K), Eocene rocks (E), and Oligocene (Gaviota Formation) rocks (0).(F, K, E, and 0 shown as dotted and buried contacts)- The fault (diamond) was either buried or was continuously or sporadically active during the deposition of the Tertiary rocks shown in Figure 2c.

                                                               '\

Subsequently, a series of pull-apart basins may have developed along the present coastal part of central California, one such basin being the Santa Maria-Lompoc 5hz basin. The Santa Maria-Lompoc basin was probably later transected bySan zone Simeon-Hosgri faultv(Eall, 1975a). After deposi.tion of the Obispo-Tranquillon volcanic rocks, the formation of the Santa Maria-Lompoc basin (Fig. 2d) began . with the development along the right-slip transform Lompoc-Solvang-Santa Maria River-Foxen Canyon-Little Pine fault system, or there was renewed movement along this already extant fault system, 'possibly during the Luisian A e (14 m.y.b.p.). The margins of the basin were formed by the.Lompoc-Solvang fault (diamonds) (or pull-apart shoulder) and the Santa Maria River-Little Pine fault (triangles) (or . pull-apart shoulder). Right-slip along the fault probably accompanied dip-slip and the late Miocene and Pliocene seas flooded the deepening basin; note that near Los Alamos the base of the Monterey Formation is nearly 4,572 m (15,000 feet) below sea level (Fig. 1), that the maximum subsurface thickness of the Monterey Formation is probably more than 1,524 m (5,000 feet) thi.ck, and the maximum out-crop thickness at the margins of the basin is approximately 655 m.(2150 feet). It is suggested that the Santa Maria River and Lompoc-'Solvang faults are part of the same transform-right lateral fault system and before the late Miocene pull-

apart, to produce*the Santa Haria-Lompoc basin, were probably a single fault or fault zone. The formation of the late Tertiary pull-apart basin, with motion t vectors of extension parallel to the strike-slip faults, began following the deposition of the Obispo (Tranquillon) Formation, probably during. the middle Miocene (14 m.y.b.p.). Halls along the fault margins may have begun to sag and pull apart as early 'as the early Oligocene, or even earlier if there was more than I one episode of rifting. The Franciscan rocks are weak, easily folded, faulted, and stretched or became even more tectonically brecciated. What occurred to the deeper crustal layers is unknown, but there was not massive extrusion. During t¹ opening of the basin only minor volcanic flows or intrusions (e.g., those. near Point Sal) occurred contemporaneously, with the pull-apart and'the stretch-ing of the F"anc scan. Rotational movement (Fig. 2e) or bending accompanied formation of the. pull-apart basin. This movement resulted in a change of trend of the Lompoc-Solvang fault (Fig. 2d) from northwest to east-west (Fig. 2e). The rotation or bending ~~ould account for the distribution fo the Cretaceous (K), Eocene (E), and Oligoce"e (0) rocks south of the inferred Lompoc-Solvang fault and may have played a role in or during the general development of the Transverse Ranges. Th amount of counter-clockwise rotation is reduced if the 'Lompoc-Solvang fault initially had a more westerly trend. The'maximum pull-apart is between 40 and. 50 kilometers. Because of probable strike-slip along the Lompoc-Solvang-Santa Maria River-Little Pine faults, the Cretaceous and Eocene rocks, Gaviota Formation, Vaqueros Sandstone, Rincon Shale, and Obispo-Tranquillon volcanic

                                                                   'I rocks near Point Arguello probably were             in closer juxtaposition,.initially with rocks of the     same   lithology     and ages   at the latitude of    Camuesa  fault (Fig. 1) or near   Zaca Lake. (Jennings,         1959) .than with rocks near the Santa Maria River fault. That   is,   the rocks"south of Lompoc and Solvang, in the Transverse Ranges, have moved along a       right-slip transform       Lompoc-Solvang-Santa'Haria      River-Little

8 Pine fault, the basin opened along this fault, rotation or bending occurred, and the Lompoc-Solvang fault and rocks south of the fault were brought into their present position. Left-slip occur'red at a later time along a Santa Ynez-Pezzoni fault system (partially shown in Fig. 1). Following the deposition of the 'late Tertiary sediments (Sisquoc,'oxen, Caxeaga formations), within the deepened basin, a part of it was zone moved more than 80 km to the north along the San Simeon-Hosgri fault (Hall, 1975a). It is unlikely that. the slip is less than 80 km. Evidence for this unlikelihood is provided by the fact that the package of rocks, in the Santa Maria region (i.fe., Jurassic ophiolite., chert, and shale, Lospe Formation, Monterey Formation, and zone 'liocene rocks), which were moved north along the San Simeon-Hosgri fault has a distribution limited to the Santa Maria basin. At its widest the basin is about 50 kilometers (30 miles). However, it will be noted that the known dis-tribution of the Jurassic ophiolite, chert, shale, Lospe Formation and associated younger rocks tha- crop out near Point Sal are known from the subsurface in an area of less than 19 km (12 miles). The distance between Point Sal and the San Simeon area (Fig. 3) is mo e than 100 km (62 miles), the diameter of the unique package of rocks in the Santa Maria area is less than 20 km, thus the offset would be at least 80 km, and more likely 95 km. The releasing half bend, depicted at the southeast end of the pull-apart basin in Figure 2d, would have had a mirror image at the northwest end, but this has been truncated by the'an Simeon-Hosgri fault and is now 100 km to the north at San Simeon (Fig. 3). The Pliocene Careaga Sandstone at San Simeon suggests that the 80 to 95 km of right-slip along the San Simeon-Hosgri fault occurred during the last 5 m.y. The earliest'strike-slip movement along the San Simeon-Hosgri fault would probably be 9 to 13 m.y. 'learly all movement took place along the fault If following the formation of the pull-apart structure.

~ p ~ ~ Some

                                ~                                           ~

investigators have suggested that the offshore exploratory well, Standard-Humble ffl (Fig. 3), contains a section of rocks that is most like that onshore at or near the same latitude (Santa 'Feria Valley). The off-shore well encountered the following section: top of the Sisquoc at 3402 ft (thickness 635 m or 2082 ft); top Monterey at 5484 ft (thickness 358 m or 1176 ft); top of volcanicash (probably Obispo-Tranquillon volcanics) at 6660 ft (thickness 122 m, or 400 ft); top of "volcanic rocks" (probably Lospe, personal communication David Howell, 1977) at 7060 ft (bottom of well at 7797 ft). Onshore, at or near the same latitude, well data (Woodring and Bramlette, 1950, cross section A-A') provide information to show that the Monterey Fo~~~~tion lies either on the Lospe or directly on Franciscan rocks; whereas the well probably contains volcanic ash,'of the Obispo or Tranquillon volcanic rocks. The section in the offshore well might best be correlated on land with rocks either south of the Lompoc-Solvang fault (i.e., near Point Arguel" o; see Dibblee, 1950, geologic map) or possibly witn the Standard Oil "Sh~-.-ers":"-1 south of Purisima Point(section 4 T.7S., R.35W.),

                                                          /herc.

more than 32 km (20 miles) south of thewell on the opposite-side of the the S~gv~ro San Simeon-Hosgri fault zone. The partial log of well shown in Figure 1 is probably incorrect 'I and the units encountered were probably Monterey overlying Obispo-Tranquillon volcanics, which in turn overlies the Lospe Formation. The well was drilled in 1928 and 1929. Thus, the offshore well could easily support but does not detract from the model of a pull-apart basin and offset along the San Simeon-Hosgri fault measured in tens of kilometers. Continuous or renewed late Tertiary or Quaternary movement must have occurred along the Santa >faria River fault. Evidence for this suggestion

is provided by the geology in the Twitchell Dam quadrangle 01all, 1977) and the geomorphology and late Tertiary and Quaternary geology along*the Foxen Canyon fault (Fig. 1). In the Twi.tchell Dam quadrangle the Rest Huasna fault faults Quaternary deposits and is in turn truncated by, or is the same age as, the Santa Maria River fault. OTHER NEARBY REGIONAL BASINS The Morro Bay basin to the north of Santa Maria basin (50 km north of Santa Haria) shows similar relationships to the development of the Santa Maria basin. Although the correlation of rocks at the margins of the Horro Bay Tertiary oasin is not as clear as those at the, margins of the Santa Maria-Lompoc basin, the Horro Bay basin might also represent a pull-apart structure. The basin may have begun to open during the early Oligocene and the dacite-felsite rocks of that age, forming Horro Rock and 12 to 13 other major int~sive masses in the'area (including the Cambria Felsite), may reflect a period of volcanism and intrusion at depth during basin opening. Such a. interpretation would have to account for the fact that the rifted intrusive rocks were dacitic and not basaltic rocks. Equally as speculative is the suggestion that the Horro Rock-Islay Hill complex (Ernst and Hall, 1974) was rotated 10 to 15 degrees to the west after emplacement, and that the Cambria Felsite in Cambria and at Rocky Butte'Hall, 1973, 1974, 1975b; Hall and Corbato, 1967; Hall and Prior, 1975)

were aligned

                        ~

with the lforro Rock-Islay Hill complex

                                                             ~at the time of    emplacement during the Oligocene. An  alternative explanation for the Horro        Bay  basin is k

that it is an uplifted, tipped fault wedge basin (see Crowell, 1974) bounded by the Pismo and Huasna inclined subsidence basins. Such a suggestion does not preclude pre-mid or late Miocene counterclockwise rotation. If the'Horro Bay basin is an uplifted tipped basin, it must have subsided during late liiocene or Pliocene time because remnants of rocks of these ages are present within the regions bounded by the Edna-Los Osos Valley and West Huasna fault systems. These faults form the margins of the hlorro Bay tipped fault wedge basin. Sb~MARY Based on the geology, stratigraphy, distribution of sedimentary and vol-canic rocks, and lithologic similarities of widely separated rock types, there is evidence to support tne hypothe'sis that the Santa?4ria-Lompoc basin is a pull-apart structure. The fault-bounded basin is wedge-shaped with the maximum pull-apart being nearly 50 km. The basin may have undergone recurrent periods of r'ing, perhaps during the deposition of the Rincon Shale, the most recent of which took place approximately 14 m.y.'b.p- The present location and orienta-tion of the Cretaceous to middle Miocene rocks in the Western Transverse Ranges are due to right slip along the Lompoc-Solvang-Santa ?faria River-Little Pine right lateral transform, subsequent counter-clocLmise rotation or bending of the region, and late Tertiary and 'Quaternary left slip along the Santa Ynez fault. T Other basins in the region, e.g. Pismo and Huasna, are possibly tipped sub-sidence basins (Crowell, 1974) and the Morro Bay basin is a tipped fault wedge basin (Crowell, 1974). All structural basins were probably formed between large strike-slip faults during late middle or late Hiocene and were in part later affected by movement along such faults as the San Simeon-Hosgri fault aone

12 and Rinconda,Fault (Dibblee, 1976). There has apparently been at. least 80 or Qoaa 95 km of right slip along the ~L~~i~>~-~~>~<< ~~Itsince the Pliocene (during the last 5 m.y.) and following the formation of the Santa Maria-Lompoc pull-apart basin. ACKNOWLEDGi1ENTS I wish to thank J. C. Crowell, W. G. Ernst, W. R. Dickinson, and Eli Silver for their helpful comments and discussions of the concepts expressed in this paper.

13

                .  ~

REFERENCES Crowell, J. C., 1974, Origin of late Cenozoi'c basins in southern California, in Tectonics and Sedimentation, edited by W. R. Dickinson: Soc. Econ. Paleontologists and Mineralogists Spec. Paper no. 22, pp. 190-204. Dibblee, T. W., Jr., 1950, Geology of southwestern Santa Barbara'ounty, California: Calif. Div. Mines Bull. 150, pp. 1-84, maps ~ Dibblee, T. W., Jr. 1976, The Rinconada and related faults in the Southern California Coast Ranges, California, and their tec-tonic significance: U. S. Geological Survey Professional Paper 981, 55 p. Ernst, W. G., and Hall, C. A., 1974, Geology and petrology of the k Cambria Felsite, a new Oligocene formation, west-central Calif-ornia Coas" Ranges: Geol. Soc. America Bull., v. 85, pp. 523-532. Hall, C. A., Jr., 1975a, San Simeon-Hosgri fault system coastal Cali-fornia: Economic and environmental implications: Science, v. 190, pp. 1291-1294. Hall, C. A., Jr. 1975b, Geologic tfap of the San Simeon-Piedras Blancas region, San Luis Obispo County, California: U. S. Geological Survey Misc. Field Studies Map MF 784, scale 1:24,000. Hall, C. A., Jr., 1977, Geologic Map of the Tw>>4~ii ><~ >>" P~">~ ~k >~= ~"" " gd TePuSqaef Puadringlc>> Santa Barbara County, California: U. S. Geological Survey Misc. Field Studies Map, scale of 1:24,000 (in press).

                'I References    continued Hall,  C. A., Jr. and Corbato,    C. E., 1967, Stratigraphy'nd structure of Mesozoic    and Cenozoic  rocks, Nipomo Quadrangle, Southern Coast Ranges,   California: Geol. Soc. America  Bull., v. 78, p. 559-582.

Hall, C. A., Jr. and Prior, S. W., 1975, Geologic Map of the Cayucos-San Luis Obispo region, San Luis Obispo County, California: U. S. Geological Survey Misc. Field Studies Map kfF 686, scale 1:24,000 Jennings, C. V., 1959, Geologic Map of California, Olaf P. Jenkins Edition, Santa ~faria Sheet. I Jennings, C. H. and Strand., R. G., 1969, Geologic Map of California, Olaf P. Jenkins Edition, Los Angeles Sheet. Turner, D. L., 1970, Potassium-argon dating of Pacific Coast Miocene foraminiferal stages: Geol. Soc. America Spec. Paper 124, pp. 91-129. Voodring, H. P., and Bramlette, M. N., 1950, Geology and paleontology of the Santa Maria district, California: U. S. Geological Survey Prof. Paper 222, 142 pp., maps.

Western Santa Santa Maria- Cuyama-Santa Maria-A e of rock units Ynez Mountains Lom oc basin Sis uoc Rivers area Pliocene Careaga Sandstone Pliocene Poxen Hudstone Miocene-Fliocene -Sisquoc Fm. Sisquoc I'in. Miocene Monterey Pm. Monterey I'm. Monterey Fm. Miocene L. Mont. I'm. Pt. Sal Pm. Pt. Sal Pm. Miocene Tranquillon Obispo Fm. Volcanics Oligocene-Miocene . Rincon Shale Rincon Shale Oligocene Vaqueros Ss. Vaqueros Ss. Oligocene Sespe/Alegria Sespe-Lospe Sespe Pm. Pormations Formations Oligocene Gaviota Pm. Eocene Eocene rocks Cretaceous . Cretaceous rocks Cretaceous rocks Jurassic Honda Fm. 'Knoxville" Fm. Jurassic shale Cretaceous-Jurassic Franciscan rocks Pranciscan rocks Franciscan rocks or Jurassic or ophiolite Table 1 Generalized pre-Pleistocene stratigraphic sections from the margins of the Lompoc Santa Maria basin, western Santa Ynez. Mountains (Dibblee, 1950), Santa Maria and Lompoc basins (Woodring and Bramlette, 1950), and the area north of the Santa Maria River (Hall, 1977), Santa Barbara County, California.

                     "~                                                                            L C

16 I FIGURE CAPTIONS I I' FIGURE l. Generalized paleogeologic map (pre-Monterey Formation and generalized structure contour map. (base of ifonterey Formation), San Luis Obispo and Santa Barbara Counties, California. Generalized distribution of selected stratigraphic units is from Jennings (1959), Hall (1977),.re-

              .donnaissance    . geologic mapping       in the     Sisquoc and Lompoc areas,       and from core hole data supplied by the California Division of Oil and Gas, from well logs Santa Haria District Office. Incomplete well data are shown: i~lon-terey Formation,      Tm;   Point Sal Formation, Tps; "Temblor" Formation,,

Tt; Rincon Shale, Tr; Vaqueros Sandstone, Tv; Lospe Formation, Tl; Franciscan rocks, KJf; Jurassic shale, Jsh; Jurassic ophiolite, Jo. A. Sylvester (Univ. Calif., Santa Barbara) reports (personal communi-cation, 1977) the presence of a fault in the vicinity of Santa Ynez

            . and Solvang    with   a  northwest trend.           I believe  that this fault is 4

a continuation oz the Pezzoni fault and passes near Los Alamos; -the exact location, however, is unknown;

                                                                'I FIGURES  2a-2e.      Hypo the tical   paleogeologic maps.

Figure 2a. following or during the deposition U Hypothetical paleogeologic map of the Gaviota Formation of Oligocene age. Coastal part of California. Figure 2b. r Hypothetical paleogeologic map, following strike-slip along the Lompoc-Solvang-Little Pine fault and before the deposition of the 7 Sespe-Lospe formations. Coastal part of California in the vicinity of what is now northwestern Santa Barbara County. The initial trend and amount of strike-slip is not known.

Figure 2c. Hypothetical paleogeologic map following deposition of the Obispo-Tranquillon volcanic rocks. Following deposition of the Ga'viota Formation and strike-slip on the Lompoc-Solvang fault, the Sespe (and the marine equivalent Alegria) (coarse swirled dots), Vaqueros (fine random dots), Rincon and Obispo-Tranquillon rocks (fine mixed dots) were successively (northeast-southwest trend) and unconformably deposited upon the underlying Franciscan (F) (vertically ruled), Cretaceous (K) (horizontally ruled), Eocene (E) (no pattern), and some Oligocene (0) (diagonally ruled) rocks. Figure 2d. Hypothetical paleogeologic map showing geology of northwestern Santa Barbara County approximately 14 m.y.b.p. Basin pull-apart began to develop along the Lompoc-Solvang-Little Pine fault con-te-poraneously with the birth of the Santa Maria River-Foxen Canyon-Little Pine fault zone. Vaqueros, Rincon, and volcanic rocks are at the margins of the opening basin, but are removed, except for remnants left on the stretched and tectonically mixed Franciscan t

       ; rocks, from the center of the basin.            Cretaceous,   Eocene, and Oligo-cene rocks along    with the overlying       Sespe,   Vaqueros, Rincon and Obispo-Tranquillon rocks are southwest of the Lompoc-Solvang-zone Little Pine fault     (diamonds); Franciscan and remnants of the Sespe rocks lie between     the two    faults,  and Cretaceous,     Sespe,  Vaqueros, Rincon, and Obispo rocks       lie  northeast of the Santa hfaria River-Foxen   Canyon-Little Pine fault zone           (triangles). Strike-slip probably accompanied the development          of the pull-apart basin.

                                                                                     ~ '   ~  ~

18 Figure 2e. Generalized pre-late Miocene 'paleogeologic map. The proposed model suggests the counterclockwise rotation of the Lompoc-Solvang-Little Pine fault, rotation that has occurred some time since the late middle pliocene. The inferred Lompoc-Solvang fault in the proposed model is the northern boundary of Transverse Ranges in the western part of Santa Barbara County. FIGURE 3.. Location of the San Simeon-Hosgri fault z'one, Santa Maria River, Lompoc-Solvang, and other faults., Spots (Ti ~ Tertiary intrusive) indicate sites of Oligocene hypabyssal volcanic rocks, including the iforro Rock;Islay Hill volcanic rocks and similar rocks in the north near Rocky Butte. Location of Standard, Oil Co. of California-Humble Oil Co. "Oceano 81" is shown west of San Simeon-Hosgri fault system.

GENERALIZED PALEOGEOLOGIC MAP 'tPItE MOilTEREY I'ORMATIONl AND GENERAI.IZED STRUCTURE CONTOUR MAP (13ASE OF MONTEREY FORMATIONl SAN LUIS OBISPO-SAN'I'A 13AR13ARA COUNTIES, CAI.IFOI~WIA On/ EXPI ANATION Oara~ '-": I;Wa:I Haaaaa faall Oll QGUAoALupE Cretaceous rocks f=".. ] Vaqueros Sandstone- Franciscan melange-

              'I       4 Oooo ll P GET TERAVIA 4     X<~          P;)       LB4/(   l I-'-.:M Rincon Shoto .
                                                                                                                                             .'espe-Lospe I

Formotion Jt s ophiolile complex Serpenlinile Jo 3 i>> a II Eoo Limit of Monterey

                                          'o        QORCUTT            .                     0     X~~ip                                                                                  Limit of Lospe
            /io Formotion
                  ~
                               ,p/~~ 4 /                               o CASMALIA I-                                               'i            iX             ~~           ~                                    In<<- Structure
                                                                                                                        ~                                                     
                                                                                                                                                        .:-:-                                        contour line
                                              'EE X       'e, 0

Cp ,.4 K= < i 'a~Neo T~ ~ EE fpu// Fault PIIrisimo Poinl

                          ~ ~       ~                                                                                                                                         o Lompoc-Solvang o   >                       faults 6~                                                                    Q LOS ALAMOS                                 ~(                                      ~ Santa     Mario River fault o

Ia

• KJt Tm s rn ( 4nl V~ 4 Exploratory oil well o u//

o~ BOE

                                                                                                                                                       +~'

Haaaa Iaa ~

                                                                                             +    L, ~~          ~OBUELLTOU              OOOUTO   Tl,'EE+         BBITBBE forll E                                                                                                                                                                 pro/jr 4

Rjnt ~EE nx E Arguelio ~ ao 4 T

                                                                                                                                                                              $ onto        )n   -~              f
                                                                                                                                                                                                               ~<u//

0C~ -"-+ 4 Q~(OIIO -- ~ /GAVIOTA PASS 0 5 50 foulg miles Oy

                                                                                                       /                                                  0            5       t0        15 km.
                                                                    'a Poiflt Coneepifen                                                Pacific Ocean

                                                                                        =CRI TACEQUS'OCENE FR ANCISCA ROCKS        1
                                                                                                                                                                                 'll OLIGOCENE                                                                                                          EOCENE lGAVIOTAl OLIGOCENE x fGAVIOTAl 8/8/1 zr g fl lit                  e     ~

e '-'":: OBISPO-'.."': " . ",ir-" lt 'rer

                                                                   !ii          ~,     '     e K                                         I
  . TR.4iQLILLO<<,,
                                                                                                 ~

rt

                                                                                .:;,"    .': 'OBISPO                              .                                                    fr[!tile
                                              't    "~llj jt f

'.-'TRAhQUILLOtr .

l!~jm~ e I SES PF

                                                                                                                                                                                               ~ ~

tt e jhT re e

                                                                                                                                                                               }               t~

e rr ej ec~ te

rr tr

                                                                                                   '::.',                   ..'.: ';, .":::e."!",,:;.'-',li, vAQUERQsgll e

r'j li te SE S Pi fj Cef ji iGi c ':,".e:,t'.::~..:.;![i rf tt t

                        ', i'..',.-,*",.<<,,,;.'e',.";! "Y.;:-,.":,"::.;

t~ OaIS II

                                                        -     Cf.

J!,l,

                                                                     )

t t l<!.~ RZ'.-CO'~ t i gll,lijff!e.ll!i~ l '! l,l ljf,' j!-;-SFRPEj i~"- Rr~ro~",.'-',-" OBISPO-TH A NQUILL'Oi

                                                                                                                      ;... VAQUEROS I-20

I

           ~     ~

36o Cape Son Martin '.

                                       ~      ~
                                         ~      ~~

ee ~

                        ~ ~           ~     ~      ~
                                             ~       ~
                                               ~       ~~
                          ~~                     ~

Rogged Pt. l

                              ~e ~
                              ~ ~ ~~
                               ~ ~
                                ~ ~

Pocky Tj(dOC te) pt. Piedros Blancos San Simeon Son Simeon Pt. Poso Robics Dc

                                                                    '. +    Cambrio Oil       OG
                    ~ eeI Morro Boy (0

.(q ~

e

                           ~ C~  ~
                            ~

p Pt. Buch Vp~ Pt.~ Son Luis C0 ~

                                                                                                       ~

ee Arroyo p PG

                                                                                                ~
                                                                                                 ~
                                                                                                  ~ pee' ~ ~ e~
                                                                                                           ~ ee ee ~                  ~~                      6 ronde                          0
                                                                                                    ~                     ee CD                          ~   W
                                                                                                     ~ ~~ ~ ~
                                                                                                              ~
                                                                                                                  ~                           Sp0              IL
                                                                                                      ~      ~
                                                                                                                    ~

0 0Gg

                                                                                                                                                             +oOq.

35o Stondard-.Humble . Oceano Nl + '-.

                                                                                                              'e 0                                            Santo              4@~

e Morio 04/

. ~Pt. Sal 0 lQ miles e Heod 0 10 kilometers

                                                                                                                     ~    ~

Purisimo Pt. Santo Morio-e ~ ~ ~

                                                                                                                              ~ ~~ ~
                                                                                                                               ~
                                                                                                                                ~
                                                                                                                                     ~
                                                                                                                                      ~

Lompoc Basin Pb Ar uello

                                                                                                                                  ~
                                                                                                                                   ~ ~~ ~ e ~ e
                                                                                                                                    ~ ~ ~
                                                                                                                                                       ~7                ~~

Lompoc Map

                                                                                                                                                 ~e Location                                                                                                                                   ee        e~

ee

                                                                                                                                                      ~          e~

eeee

                                                                                                                                                        ~          ee
                                                                                                                                                           ~e
                                                                                                                                                              ~e Pt. Conception:,                ~ e 2lo

~' II

       ~    ~

ATTAC11MENT J I

~
  ~

MARINE GEOLOGY AND TECTONIC HISTORY OF THE CENTRAL CALXFORNIA CONTINENTAL MARGIN Eli A. Silver 2 Santa Cruz, California David S. McCulloch 3 Menlo Park, Cali fornia Joseph R. Curray 4 La Jolla, California ABSTRACT The geology of the central California continental margin shows a history of early Tertiary subduction of the Farallon plate k and followed by a Miocene and younger period of high angle faulting and basin formation corresponding to transform movement between the Pacific and North American plates. Seismic reflection profiles show irregular structural surfaces on the older sedi-mentary rocks, which are overlain-by mildly warped younger strata. shelf basins, including the Santa Maria, Sur, Outer Santa

                                                                                     'arge Cruz, Bodega,      and Pt. Arena basins, are bounded by down-to-basin faults. The structural style of most'f these basins is similar, although the Pt. Arena, Outer Santa Cruz, Santa Maria and Sur basins probably rest on Franciscan basement and the Bodega          lies on   granitic  basement.

Drilling data suggest. a nearly synchronous origin for these basins in 'middle Miocene time (Hoskins and Griffiths, 1971) . Analysis of pi..esently available data for the history of finite plate movements since the middle Cenozoic suggests a westward shift in the direction

of movement of the Pacific plate relative to the North American plate in this region about 10 million years ago (m.y.a.). Such a change in plate motion could have provided a sufficient extensional component of movement to result in basin formation, possibly along the older structural grain of the margin. Some of the Quaternary faulting is high angle reverse in sense, indicating a compressional component acting over approximately the last million years. lt is possible that the instantaneous movement between the Pacific and North American plates has been changing continually during the past 30 m.y. The distribution of granitic rocks of the Salinian block on the continental margin constra'ins measurements of offset along the San Andreas and San Gregorio faults. The San Andreas system of faults shows at least 550 km and a maximum of 600 km offset, based on the northern extent of granitic basement under-lying Farallon ridge. The San Gregorio fault has an estimated offset of 100 + 15 km, based on offset of the southern end of Farallon ridge. These observations support the idea of slivering within the Salinian block (Johnson and Normark,.'1974). However, early Tertiary paleogeographic reconstructions by Nilsen and Clarke (1975) require some Salinian offset by early Paleocene, in contrast to the model of Johnson and Nomark. We favor approxi-mately 100 km of offset during latest Cretaceous to Paleocene time and 450 to 500 km offset after 22 m.y.a. Granitic boulders dredged from Santa Lucia Bank, far west of the Salinian block, raise the question of either the presence of granitic fault slices west of J-2

     ~   ~

I ~ 1 the Salinian block or exten ive transport of these boulders from Salinian source areas.

Manuscript Received Accepted

2. University of California, Santa Cruz, California 95064

3. U. S. Geological Survey, Menlo Park, CA 94025

4. -

Scripps Xnstitution of Oceanography, La Jolla, CA 92093 We thank W. R. Normark and H. C. Wagner for careful reviews and suggestions. D. G. Moore, R. von Huene and H. G. Green'e generously allowed, use of unpublished reflection profiles, and the National Ocean Survey generously allowed use of unpublished gravity and magnetic data. We are grateful to T; C. Worsley for paleonto-logic analysis, to L. Silver, E. C. Beutner and L. Lee fox petrologic examination of some of the rocks collected, and to C. McHendrie and Robert Brune for a great deal of effort in providing computer output of much of the data. We are grateful for discussions with and ideas from,C. G. Chase, T. Atwater, S. A. Graham, W. R. Dickinson, W. Gawthrop, C. H. Hall, D. Hamilton, J. Crouch, E. C. Bcutner, J. C. Crowell, T. Nilsen, and to a great people, too numerous to mention or to properly recall, J'any who contributed to thi+ work in very significant ways. Our lack of citation here is not through lack of gratitude or indebtedness. We finally thank the captains, crews and scientific parties of many expeditions to the rolling seas off central Califor'nia for their cooperation and support.

INTRODUCTION The continental margin off Central California, between the Mendocino and Murray fracture zones, has undergone a complex tectonic development during Cenozoic time. Atwater (1970) has interpreted the magnetic anomaly pattern in the northeast Pacific to imply subduction of the Farallon plate (McI(enzie and Morgan, 1969) beneath the margin in the early Tertiary. Approximately 30 m.y.a. subduction began to cease along Central California and strike slip faulting subsequently began along the margin. I These tectonic processes probably played a major role in develop-ing the structure of the margin. The present study describes that structure and evaluates hypotheses for the Cenozoic tectonic,. evolution of the continental margin. Geophysical study of the margin has included single channel seismic reflection profiling, utilizing high and low energy sound sources, on approximately nine expeditions of the Scripps Institu-tion of Oceanography'nd of the U. S. Geological Survey since 1964 (Fig. 1). Additional detailed studies are available for Monterey . Bay (Greene, 1970), at Point Arena (unpublished Pacific Gas and Electric Company report) and between Point Arguello and Point Sur (McCulloch and others, 1977; Buchanan-Banks and others, 1978). Gravity and magnetic data were obtained between San Francisco and Point Arguello and magnetic data north to Cape Mendocino. We were fortunate to have access to an extensive gravity, magnetic and bathymetric survey done in 1970 by the National Ocean Survey.

Sea. floor rocks were obtained by dredging (Fig. 1) on Antipode and Seven-Tow expeditions of the Scripps Xnstitution, on several U.S.G.S. expeditions of the R/V Kelez and R/V Bartlett and from previous workers (Hanna, 1952; Uchupi and Emery, 1963; Martin and Emery, 1967) . Hoskins and Griffiths (1971) hereafter ~ abbreviated as (H-G) published structural interpretations of shelf basins based on Shell Oil Company seismic profiles, dart cores, and well data. The data were not available to us, but we have used their published maps and cross sections for age control whenever possible. For convenience of'resentation of the geophysical results and structural interpretation we divide the Central California continental margin into three regions: 1) Point Arguello to Monterey (34 to 36.5'N); 2) Monterey to Pt. Reyes (36.5 to 38'N);

3) Pt. Reyes to Cape Mendocino (38 to 40.5'N).

GEOPHYSICAL RESULTS Point Arugello to Monterey The dominant structural features of this part of the conti-nental margin'are the Santa Lucia bank and the Santa Maria and Sur basins (Fig. 2). The bank is a broad high bounded on the Gast by the Santa Lucia bank fault (Figs. 2 and -3) and on the west by the top of the continental slope (see profiles 16-28, Fig. 4). The Santa Maria basin offshore lies between the Hosgri and Santa Lucia bank faults (Fig. 2). The Sur basin is continuous

~ li ~ ~ h with the Santa Maria, is bounded by coastal 'faults on the east (Fig. 3), and sediment thins westward against the northern part of Santa Lucia bank (Fig. 5,'2-L10).. The basins and bank make up the Arguello Plateau (Uchupi and Emery, 1963). The structural development of the region was discerned from the geo-physical data, but the timing of tectonic events relies on data from the geology of the onshore Santa Maria basin, offshore drilling by oil companies (H-G), and dredging. The Sur basin (Figs. 2, 3) is crossed by profiles L2-L10 (Fig. 5,) and has greatest sediment thickness in profile L6. The ediment thickens eastward, with more than. three kilometers of sediment very near the coast. The shelf is narrow here, and is probably bounded on the east by a fault. The fault is suggested by the vertical offset in Franciscan rock that probably underlie the Sur basin offshore, and are exposed along the coastline, an offset of at least four kilometers. The fault is also sugge ted by a steep gravity gradient (Fig. 6) . The near absence of deformation in these basin strata, and the ease of acoustic penetration suggests that the layered section on line L6 is largely of late Cenozoic age. H-G (1971) interpret the base of the layered section to be lower Miocene. An uncon-formity occurs within the section in line L2'(Fig. 5) but its age is not known. The Santa Maria basin is developed on lines L12 to L20, and in many profiles sediment thickness is greatest at either edge of the basin (see lines L16, L18, L22, L24, L26), as sediment wedges thicken toward and terminate against the faults that

At least two unconformities are seen in lines N bound the basin. L14 to L28, especially well displayed in lines L16 and L20 (Fig. 4). The lower unconformity probably separates Miocene and younger rocks from pre-Miocene rocks. The upper unconformity may be late Miocene or Pliocene. An unconformity separating early Tertiary from late Cenozoic (undated) rocks is beautifully displayed on lines L20, L22 and L24. The Santa Lucia bank fault forms the western boundary of the basin for about 150 km. The fault has its greatest physiographic expression in line L20 (Fig. 4) where the 'sea floor is offset about 150 m. To the south the fault, nearly intersects a west trending fault that bounds the north side of the channel islands platform (Fig. 3) . However, the relation betvreen these faults is not clear. The east side of the basin is bounded by the Hosgri offset fault'Nagner, 1974), which can be recognized as a major*basement on the inner parts of lines L16 to L26. Shallow water depths and ringing multiple reflections in some profiles act. to obscure the structure. The Hosgri fault is probably seismically active. An earthquake of magnitude 7.3 occurred in the vicinity of southern Santa Maria basin in 1927, and Byerly (1930) reports that a tsunami occurred along the coast of southern California following the earthquake. Recent relocation studies (Gawthrop, 1977) place the 1927 epicenter at the southern end of the Hosgri fault. The Hosgri fault trends northward toward the San Simeon fault on land and is probably continuous with it. Hall. (1976) presents evidence for right lateral offset of 80 km to 100 km by matching 1

geologic sections at San Simeon west of the fault and Pt. Sal, 80 km south and on the east side of the IIosgri fault. The section is Jurassic through Pliocene and rests on Jurassic ophiolite (Hopson and others, 1973). The exact location and behavior of the Hosgri fault between San Simeon and Point Sur is uncertain, but the fault is probably continuous and may continue north to or be en-echelon with the San Gregorio fault, described below. Basement rocks appear to directly underlie upper Cenozoic deposits in the central part of the Santa Maria basin. Profiles L16 and L18 show an arched basement reflector which correspond with a gravity high and magnetic anomalies of up to 200 nT (Fig. 7). A crustal model fitted to gravity data on line L18 is satisfied by a high density (2.85 gm/cc in this model) block in the central part of the basin (Fig. 8). Shallow basement beneath the basin is indicated by paired magnetic anomalies that are elongated parallel to the basin but confined between the Hosgri and Santa Lucia bank faults (Fig. 7) . The western anomaly is positive (> 100 nT) and the eastern is negative (> -100 nT). The negative magnetic anomaly coincides with the high density block and may b'e caused by basaltic x'ocks of the Franciscan assemblage perhaps part of the Pt. Sal ophio-lite described by Hopson and others (1973). It now appears critical to drill the section over this reflector to see whether it. is similar ox different. from the sections matched by Hall across the Hosgri-San Simeon fault as a test of whether those sections are truly of fset 80 km or have continui ty offshore. \

 ~ 4 ~

I ~

                                                                    ~~

Just east of the Hosgri fault is a series of NW-trending faults that strike into the Hosgri at an angle but do not cut, the large fault. Some of these small faults possibly cut. Holocene sediments (Wagner, 1974), suggesting that both fault trends may be active. The age of the Santa Maria basin is repor ted to be late middle Miocene on the basis of drilling by Shell Oil Company (H-G) . This age dates the relative uplift of Santa Lucia bank on the western margin of the basin. Woodring and Bramlette (1950) 'eport. that marine deposition in the present onshore part of the basin begain in the middle Miocene with the Pt. Sal formation. Marine conditions continued there through Pliocene time and major deforma-tion occurred in the Pleistocene. Local compressional deformation is seen in Santa Maria basin offshore. Figure 9 (profile LDM in Fig. 1) shows a large fold of sedimentary rock buttressed against a basement. block on its east side. The structure may have resulted from local shear between basement rocks. Santa Lucia bank forms a smooth topographic surface but has a complex internal structure. The block faulted style of the bank led H-G to postulate rigid granitic basement at depth. Seismic profiles (Fig. 4, L20 to L28), however, show a complexly deformed internal structure within the bank, suggesting an earlier phase of deformation that was neither rigid nor blocklike. Thus the bank has undergone at least two distinctly different styles of de formation.

The older folding deformation of the bank is truncated by an erosional unconformity, and in some lines (Pig. 4, L20 and L24) the block faulting po t-dates the unconformity. If, as discussed below, granitic rocks are present beneath the bank, they are more likely pxesent as small fault slides than as a continuous, rigid mass. Our profiles do not show a continuous acoustic basement beneath the bank. Three dredge hauls, D4, D5'nd D7, were taken on the bank. Dredge haul (D5) was taken on a faulted outcrop on the east side of Santa Lucia bank, crossed by profile L26 (Fig. 4). This latter dredge recovered well rounded boulders and cobbles indica-tive of significant transport prior to deposition, and also some rock fragments, assumed to be local bedrock. 'he most abundant transported boulders were meta-conglomerate, meta-sandstoneg argillite, and mafic volcanic rocks. In-place rocks included pholad-bored granitic sandstone and calcarenite, chert, and one piece of actinolite schist. The schist was very angular and

        'I easily broken and probably could not have survived appieciable transportation. David Moore (pexsonal commun., 1971) dredged glaucophane schist very neax this location. Dredge 4, located on line L16 (Figs. 1 and 4), recovered several rounded cobbles of quartz monzonite and quartz diorite. The most common rock type recovered was granitic sandstone, with lesser amounts of pholad-bored phosphorite, some siltstone, and mafic volcanic rock. The sandstone, siltstone, and phosphorite were most probably in place.

The granitic cobbles, were transported an unknown distance. In dredge D7, located on profile L28 (Figs. 1 and 4), soft granitic

sandstone was the dominant rock type recovered. The size of the granitic sandstone indicate that it was in and'ngularity place. individual grains are angular to subangular, implying rapid deposition with little reworking. Quartz and feldspar commonly show undulatory extinction, and the micas are deformed,. suggesting that the rock has undergone a significant shearing or flattening deformation. The sandstone is similar to that found within the Franciscan assemblage, which also is quartz rich, angular to subangular, and internally sheared (Bailey and others, 1964) . The granitic cobbles and sandstone could have had either a local (favored by H-G) or a distant source. Local source bodies could be either intrusions or fault slivers.' Distant. sources could be from the Salinian block (generally considered to be an offset slice of Sierra Nevada granitic-metamorphic basement, bounded by .the San Andreas and Sur-Nacimiento faults) . At the base of the continental slope, all profiles show a basin with 2 km or more of sediment fill. Profiles 16; 20, 22 and 28 show a basement, reflector passing below the lower part of the continental slope. Xn line L20, basin strata overlap continental slope debris.. The same relations occur in line L28, but here several hundred meters of strata above the basement reflector pass under the slope debris. ln line L22 the structure is partly obscured by a small fault block at the base of the slope. These observations suggest that no tectonic dislocation has occurred along the lower part of the continental slope during deposition of the upper two thirds of the basin sediment.

~ ~ An inactive, northwest-trending fracture zone offsets mag-netic anomalies, questioningly identified as anomalies 7 and 8, approximately 30 m.y. old by Atwater (1970) . The fracture zone is marked by a ridge that provides further evidence for the "stability of the lower slope region '(Figs. 3; 4, lines L18, L20, L22, and L24; Fig. 7) . The ridge extends onto the lower part of the continental slope in line L24, and dredging at this location yielded dominantly fine-grained olivine basalt and manganese nodules. These. rocks (D6, Figs. 1 and 4) are quite unlike all others taken on this margin and are clearly representative of a seamount or volcanic ridge. The dredge samples indicate that the fracture zone ridge extends to the continental slope. No appreciable lateral offset has occurred between the vol-canic ridge on the slope and the offshore fracture ridge if this correlation is meaningful. The age of the ridge can be no older than the sea floor on either side (about 25 to 30 m.y.). 1f the ridge formed close to the time of sea floor development, the most probable case, then little or no lateral offset has occurred along the Santa Lucia escarpment since the Pacific and American plates came into contact in the middle Tertiary (Atwater, 1970; McKenzie and Morgan, 1969) . Monterey to Pt. Reyes The dominant structural feature of the Monterey Bay area is the San Gregorio fault (H-G, 1971; Greene and others, 1973) which can be followed northward and offshore from Ano Nuevo Point to intersect the San Andreas fault system off San Francisco,

giving a measured length of 150 km from south of Monterey to San Francisco. The San Gregorio fault probably separates granitic basement rocks on the east in Monterey Bay from non-granitic rocks to the west (Martin and Emery, 1967; Greene and others, 1973) . East of the fault is a series of northwest-trending. faults that do not cross the San Gregorio fadult. Earthquake studies show that both these NN trending faults and the San Gregorio fault are seismically active and first motion studies show that both are undergoing right slip (Greene and others, 1973). This pattern is strikingly similar to that developed east of the Hosgri fault (Wagner, 1974; Gawthrop, 1977). Furthermore, the San Gregorio fault may be the northward continuation of the Hosgri-San Simeon fault zone described above. Xf this suggested continuity is proved correct, the aggregate length of the San Gregorio-Hosgri fault zone approaches 400 km. The San Gregorio appears to offset granitic basement terranes at least 90 km (Silver, 1974) and Miocene and older rocks as much as 90 to 115 km (Graham, 1976; Graham and Dickinson, 1977) . The of fset of the San Gregorio fault is, within the limits I suggested of error, equal to the suggested offset of the Hosgri fault, greatly increasing the probability that. they represent a single, continuous fault zone. Two ridges and two basins lie west, and northwest of Santa Cruz. 'he Farallon ridge is composed of quartz diorite at the Farallon islands and appears to intersect the coast north of Ano Nuevo Point. The ridge can be traced continuously in seismic profiles as far north as Point Arena (Fig. 2), and shows clearly

15 as a high on the gravity map (Fig. 6). The free-air anomaly reaches 50 mgal north of tho Farallon islands and drops to nearly zero southwest of Half Moon Bay. This gravity low along the'idge may mark an old erosional or tectonic notch. A pronounced positive magnetic anomaly is mapped over the southern part of the ridge ( ig. 7). The northward extension of this magnetic

             ~

high along the Farallon ridge is less intense and cannot be contoured becau e the available profiles are dominated by relatively strong, and as yet uncorrected effects of diurnal variation. The magnetic high can be recognized from profile to profile, however. The gravity anomaly is most pronounced west of San Francisco and Pt. Reyes where the magnetic anomaly is least developed. The ridge as structurally defined does not represent simply the surface expression of granitic basement. For example, line N23 (Fig. 10) shows granitic rock between two faults on the upper continental slope. The rest of the ridge in this profile is underlain by uplifted sediments of Miocene and younger age,'nd Upper Cretaceous sedimentary rocks, which probably appear as acoustic basement in our reflection profiles, crop out north of Ano Nuevo where the ridge appears to intorsect the coast. East of this ridge the Bodega basin locally contains more than 2 km of late Cenozoic sediment. The east margin of the basin is formed by high angle reverse faults, from the Pt. Reyes fault on the north to a narrow fault zone off Half Moon Bay. Profiles K44 and K66 (Fig. 11) show a buried unconformity, below which sediments aro faulted and more tightly folded than the post uncon-formity strata. Comparing our profiles with the H-G drilling ages,

the unconformity is middle Miocene. An H-G cross section southwest from Bodega Head shows thin 'lower to middle Miocene strata over the central part of the basin with westward thickeni ng. This structure indicates that the central part of Bodega basin stood high in the lower and middle Miocene. Uplift of the western margin (the Farallon ridge) and subsidence of the basin. commenced in about the late middle Miocene. The Santa Cruz high lies off Santa Cruz and southwest of the Farallon ridge, and between the two ridges lies Outer Santa Cruz basin (Fig. 2). Both the Santa Cruz high and outer basin plunge northwest (lines Sl-3, Fig. 12). To the north the high diminishes and the western margin of the basin is formed by Pioneer and Guide seamounts. A dredge haul and core (AD21 and ACD ll} recovered mafic volcanic rock from the Santa Cruz high. Outer Santa Cruz basin attains a thickness of at least 3 km. The lower layers on the west side of the basin are gently up-turned against the Santa Cruz high in line S2 (Fig. 12), but the A upper 1 km of section abuts the ridge with no sign of distortion. Probably no vertical movement of the ridge has occurred in Quaternary or late Pliocene time, based on estimated sediment ages in seismic profiles, but earlier uplift is indicated. The eastern margin of,the basin appears fault controlled (see lines K68, K93, and S1-4) but faulting affects only the deeper layers and probably has not been active since late Miocene time. This structure con-trasts with the basin edge faults bounding Bodega, Santa Maria and Sur basins, which show Pleistocene and in some cases Holocene

                                                                  'ctivity.

Dredging on the continental slope west of Farallon ridge has yielded rock and sediment of. Miocene and younger age (Hanna, 1952; Uchupi and Emery, 1963; Curray and Silver, 1971; Silver and McCulloch, 1973, unpublished data) ..Reflection profiles (Kl, K44, Fig. 11) show Miocene and younger strata passing smoothly across the continental slope out onto the abyssal plain. The sediments are cut by submarine canyons, valleys and slumps, but show little or no sign of tectonic activity. In some profiles (Kl, K44, K66), coherent reflections below the younger, regularly bedded sediment blanket may denote a folded sedimentary sequence representing a tectonic environment quite different from the present one. Some of these deep, irregular reflections are asso-ciated with volcanic rocks (K93, Sl, S3), as interpreted from marine magnetic anomalies. Atwater (1970) suggested that in early Ter tiary time the Central Cali fornia area was a region o f crustal subduction. We suggest that the folded sedimentary sequence seen on the continental slope in lines Kl, K44, K66, W19, and lines 'L-18 to L28 was deformed by subduction and sediment. offscraping in the early Tertiary episode. Subduction appears to have ceased before Miocene time because Miocene and younger strata are not deformed. Pt. Reyes to Cape Mendocino Horth of Pt. Reyes the Bodega basin is bounded on the west by the Farallon ridge, which is faulted in this region, and on the east by the Pt. Reyes fault. The Pt. Reyes fault appears as a sharp flexure in the seismic profiles (see line W23, Fig. 10)

and H-G map it as an east-dipping reverse fault. The Bodega basin in this area resembles the Santa Maria basin offshore in that both are bounde'd by down-to-basin faults. As with the Santa Maria basin, the Bodega and Outer Santa Cruz basins originated in late middle Miocene time (H-G) . Bo<<ga basin narrows northward as the Farallon ridge approaches the coast. Three acoustic units can be distinguished, within Bodega basin which are separated by basin-edge unconformities (profile W23, Fig. 10). The lowermost unit is most. deformed and is probably upper Miocene, based on sections by H-G. The reflectors within this unit are parallel, demonstrating that uplift of the 'basin margins or relative subsidence of the basin began in latest Miocene or early Pliocene. The overlying Plio-Pleistocene beds are less deformed and the uppermost layer shows no evidence of tilting against the ridge. Approximately two kilometers of Pliocene vertical relative uplift are indicated for the Farallon ridge ~ Granitic rocks crop out as far north as Bodega Head within the Salinian block. No granitic basement is reported north of Bodega west of the San Andreas fault, but the extent of the Farallon ridge may indicate such basement as far north as Point Arena. The ridge appears as a block-like uplift in profiles Kl and K3 (Fig. 11), and in W19 through W26 (Fig. 10) . Faults bound one or both sides of the ridge in these profiles and strata of the west side of Bodega basin are uplifted. In lines W18, W17 and N16, an unconformity truncates both the ridge and the basin strata, and Pleistocene deposits prograde across it. The

 ~    ~

~ ~ block structure of the ridge is not evident in these profiles and the upper surface of the ridge is not a hard reflector, as it is farther south. Thus, the ridge structure extends as far north as Point Arena, but gran'itic basement is followed with confidence only to approximately 38'30'N, or 50 km south of Point Arena. It remains uncertain, therefore, whether granitic rocks continue at depth under the ridge to Point Arena or ar' T absent north of 38'30'N and sedimentary rocks make up the body of the ridge. Evidence suggestive of offshore granitic basement north of Bodega was presented by Wentworth (1968) in the Gualala area where he identified coarse clastic Cretaceous sediments derived from the southwest. Such rocks under the northern part of the Farallon ridge could provide such a source. The sea floor off Point Arena is exceptionally complex. The

     ,Farallon ridge ends offshore of the point, but its northern terminus is not well defined. The San Andreas fault bends to a more northerly trend north of Point Arena, and northwest of the point'is a series of complex northwest trending folds and faults (Fig. 3) in late Cenozoic strata. These str'ata are part of the Point Arena basin of H-G.

On the west side of the basin a broad, low structural ridge, the Oconostota ridge increases in width northward. The ridge is I seen underlying a broad, low terrace near the base of the con-tinental slope (Fig. 10).'ine WX (Fig. 13) follows the ridge crest and shows the irrcgular complex structure of the ridge underlying the fairly uniform layering of late Cenozoic strata above.

The, basement rock of Oconostota ridge crops out on the north flank of Noyo Canyon (Pig. 10, line W8) and a dredge haul at this location yielded abundant graywacke. The rock is weakly foliated to highly sheared in thin section and shows chlorite alteration of the groundma s. It is poorly 'fossiliferous but contains "a few non-diagnostic Mid-Eocene to Oligocene nanno-fossils" (T. R. Worsely, written commun., 1973) . Site 173 of leg 18 of the Deep Sea Drilling Project (DSDP) was drilled on the western flank of the ridge. The hole 'pene-trated a complete section of marine strata from Pleistocene through lower Miocene or upper Oligocene(?) and terminated in andesite (culm, von Huene and others, 1973). The reflection profiles show that these Miocene and younger strata pass smoothly across the base of the continental slope and drilling indicates that depositional conditions were quiet in this area back to the early Miocene. Recovery of deformed early Tertiary sedimentary rock and of andesite from Oconostota ridge demonstrates some of'the lithologic complexity of the ridge. In line W18 (Fig. 10) the west flank of Oconostota ridge near the base of the slope abuts the acoustic'-basement reflector beneath the sediments west of the ridge and suggests that the contact between pre-Miocene continental slope material and the oceanic crust was tectonic. These observations imply that the Oconostota ridge was formed under tectonic conditions 'that have not been active since the early Miocene. J-20

The Point Arena basin as described by H-G, is bounded by the San Androas fault on the east, Point Arena to the south, the Mendocino fault to the north, but is ill def ined on its wc tern margin. >le consider the Oconostota ridge to form the western margin. The structure of this basin changes markedly from south'he north. profile N13 (Fig. 10) off Point Arena hows a section of de Qrmed deposits of probable Miocene age covering much of the;... rgin. This material is overlain uncon-formably in the hei f a d upper slope area by prograding latest Cenozoic deposits. U.-,der the shelf the unconformity dips uniformly eastward to location - where it appears to terminate against, a fault with significa."." vertical offset-Zn line Nll fol=-= Miocene rocks are truncated by an uncon formity which is in -- . folded. Beneath the shelf edge is,a basin

             'I (Fig. 10, line Nll,         'o      20 km) with thick deposits above the mity H-G r:=-= =aults with. several kilometers of vertical offs<< on either sid=- -= this basin. The basin is seen on profiles N9 th'rough N12.      The -=~logy east of the basin is complex and ob <<red by multiple --=lections on the seismic records.                 The uppor unconformity       p'=     =ave widespread extent throughout the eastern <<ge        of the   '==- ==~ and crops out or subcrops     at depths between one and two         .'c=  ..eter   below sea level. Xf this inconformit resul<<d from erosio-. =-; wave action, up             to two kilometers of su~ ~<<nce of the ea~==-> margin of point ~rena basin may be subsidence inferred for guatern=- .- "ime.
          ~"ottom ref lee---s are approximately parallel to the eea a"<<f Oconos-- = ridge and minor faulting (line N8, Fig.           10)

occurs. Profiles farther north, Wl through W7, show minor '. deformation of late Cenozoic deposits but older rocks are intern-ally deformed (line NX, Fig. 13) . The surface of the older rocks is irregular, and unlike the younger sediment, show no obvious relation to erosional channeling. A number of relatively tight folds and associated faults I trend northwest from Point Arena and die out approximately 50 km to the north, where the continental slope becomes more gentle.' major part of the deformation in this area, including the large shelf-edge basin, the folded unconformity, and faults of large vertical offset, are most, likely controlled- by tectonic processes, although some deformation may be related to downslope movement of sediment under the influence of gravity. The San Andreas Fault Zone The San Andreas fault changes orientation north of Point Arena to a'ore northerly-trend and can be traced onshore just south of Point Delgada (Curray and Mason, 1967). South of Shelter Cove six profiles (4 not shown in Fig. 1) cross the San Andreas, which offsets the sea floor with the west side up, producing a shoreward facing scarp. Another fault, two miles east has no sea floor offset. The maximum observed vertical offset on the San Andreas fault scarp off-shore is 8 m, and the relief decreases southward. The general displacement history of the San Andreas is right lateral slip, and such movement would have produced east-side-up offset since the sea floor slopes southward along the strike of the fault. Therefore the observed west-side-up topographic offset must be due to vertical movement. J-22

23

     'North of Point Delgada the location and character of the San Andreas   is  unknown.'  Nason   (1968) mapped  a number of shear   zones on, land between Point Delgada and Cape Mendocino but he could          find  no evidence   for recent   movement on the zone" near    Point Delgata. Un-fortunately, the clear geomorphic evidence for 1906 faulting at Pt.

Delgada cannot be traced across this area (Lawson, 1908). This lack of evidence may be the result of obliteration of such evidence by extensive landsliding and mass soil movement that occur in this area; or perhaps, the San Andreas does not extend onshore north of Point r Delgada as a well-defined fault. Xn this regard, Beutner and Hansen (1975) carefully examined the structure of the large inland shear zones and determined a left..lateral sense of shearing, associated with late Tertiary subduction. They also found, however, that NN-trending structures just along the coastline showed evidence for right lateral shear. Detailed reflection surveys that we have made offshore between Point Delgada and Cape Mendocino (not shown in Fig. 1) have no dis-covered definite evidence of faulting offshore between Cape Mendocino and Point Delgado. Numerous acoustic 'irregularities on the nearshore profiles may represent faulting, but the deeper structure is obscured by multiple reflections. None of these irregularities can be traced between profiles. Zf the San Andreas fault is expressed by a single trace north of Point Delgada it may run along the beach. Seeber and others (1970) show a very complex pattern of micxoseismic activity in this region. The northward bend of the San Androas presents an interesting geometrical puzzle. A fault-fault-trench triple junction like the J-23

24 I~ Mendocino is unstable unless one fault is on a straight line with the trench (subduction zone) (Fig. 14). The Mendocino should be unstable because the San Andreas fault and the subduction zone are not aligned. However, north of Point Arena the San Andreas bends northward and then, at Point Delgada, northwestward. This bending raises a serious problem in that the northerly trend, between Point Arena and Point Delgada, should be associated with extension across the. fault, as indicated in Figure 14d. . Possibly subsidence of the continental margin in this area, as seen by deep unconformities, a gentle continental slope, and a narrow shelf is a manifestation of extension. However, instead of changing the geometry of the triple junction to acquire a new stability configuration (as in 14c), the plate boundaries. appear to 1 be adjusting to maintain stability of the older geo'metry. TECTONXC DEVELOPMENT OF THE CONTINENTAL MARGIN The s true tural development of the continental margin o f Central California provides important: constraints for any . scenario of the tectonic evolution of the western United States. The structure of the lower part of the continental slope in this region shows well layered Miocene and younger'trata smoothly covering an irregular, hummocky "basement" that is at least in part, composed of deformed Paleogene sedimentary and volcanic rocks. This structural superposition is interpreted to indicate Paleogene deformation, probably related to subduction of the Farallon plate (Atwater, 1970), followed by Miocene to Holocene

i~ ~ ~ g rC tectonic quiescence along the lower part of the continental slope, Evidence for Miocene and younger quiescence is provided by the presence of a volcanic ridge along an early Pliocene transform fault (Fig. 3) that extends undeformed from the oceanic crust onto the continental slope west of Santa Lucia bank. Because the ridge shows no off et at its junction with the slope, no significant Miocene or younger shear can have occurred on the lower part of the slope if this correlation is correct. In contrast, abundant evidence is seen for extensive faulting, both horizontal and vertical, along the central and inner parts of the continental margin. An important structural feature for deciphering tectonic movements in this region is the Faxallon ridge. The granitic intrusives along the offshore ridge indicate that it is the probable offshore extension of the Salinian block, the sliver of granitic and metamorphic basement lying between the San Andreas and Sur-Nacimiento fault zones (Page, 1970). The Salinian block is generally interpreted as a slice of Sierran-type basement that has been displaced northwestward'long the San Andreas fault system (Efamilton, 1969; Page, 1970; Crowell, 19G2) although alternative hypotheses have been suggested (kIsu, 1971). If the first hypothesis is correct, then the northern extent of granitic basement rocks records the total horizontal offset along the San Andreas fault system. From the northernmost extent of recognizable granitic basement west of the fault to its northernmost extent east of the fault, the minimum slip appears to be 550 km, and from the northern extent of Farallon ridge

26 k morphology the maximum slip is 600 km (Pig. 2a) (Silver and others, 1971) . A total of fset, of 550 to 600 km along the San Andreas faul t was first suggested by Nentworth (1968) and his evidence was further substantiated by Ross (1972), based on identifying offset source terranes for conglomerates within the Gualala basin. How and when this offset occurred is only partly resolved. Right slip displacement of 300 km post 22 m.y.a. has been docu-mented on the central part. of the San Andreas fault between San Francisco and the Transverse Ranges (Huffman, 1972; Matthews, 1976) and Nilsen and Clarke (1975) documented no offset, on that segment from 45 to 22 m.y.a. Xt is important. to distinguish over what segments the offsets apply, because the available information can be explained in several ways. One is a two-stage, single fault model (Suppe, 1970) giving about 300 km of late Cretaceous to early Tertiary offset on the San Andreas fault, followed by a second, Miocene and younger offset, of another 300 km on the fault.

   . A second  model   is  a single stage-multifault history in which greater offsets can occur on the northernmost segment of the San Andreas than farther south due to slip on other, subparallel faults west of the San Andreas.

The recent studies of the San Gregorio-Hosgri fault zone indicating 100 + 15 km of right.-lateral offset .support the multi-fault model, although the offset mapped to date is insufficient to prove a single stage history. Graham (1976) mapped a maximum of 35 km right slip on the Rinconada fault bringing the maximum

documented Miocene.and younger offset on the San Andreas fault ~sstem to approximately 450 km. Activity on the San Gregorio fault may'play a major role in partitioning strain buildup in the Central California region. Studies of lateral offset of fences, roads, railroads and other linear markers after the San Francisco earthquake of 1906 showed common evidence for offsets of 5 m (16 ft) or more north of San Francisco, but only 2 1/2 to 3 m (8 to 10 ft) south of San Francisco (Lawson, 1908) . One explanation of this difference is a lesser strain buildup on the San Andreas to the south because of slip on the San Gregorio fault. The Hayward-Calaveras fault zones may also relieve strain buildup on the San Andreas system, but it is not clear why slip on this fault zone should selectively partition the strain differently north and south of San Francisco (see Fig. 3). The remaining 100 (+) km of basement offset may be explained by Miocene and younger undiscovered slip along other faults cutting the Salinian block. Their discovery would prove .the Johnson-Normark hypothesis. Alternatively, approximately 100 km of late Cretaceous to early Paleocene offset may have occurred on the San Andreas fault, as suggested by Silver and others (1971) to explain the development of the Gualala basin in latest Cretaceous time. They proposed a rhombochasm opening of an elongate basin to explain the basalt floored basin filled with. very thick, coarse elastic sediments (Nentworth, 1968). An early Tertiary San Andreas fault is also favored by Nilsen and Clarke (1975) to explain early Tertiary paleogeography and basin development in

28 ~ W ~ Central California. Development of the Basins The results of drilling in the basins which suggest a nearly synchronous origin of the central California basins in middle to late middle Miocene time (roughly 10 to 14 m.y.a.), place tight constraints on hypotheses for the origin of the basins. For example, an origin related to a southward migrating triple V junction must be eliminated. here because the timing of this migra-tion was over a period 8 to 10 m.y; long from about 29 to 20 m.y.a. in this region. The age data give no indication of an age progression in the origin of these basins and the timing (10-14 m.y. 'vs. 29 to 20 m.y.) is between 6 and'20 m.'y. too late for this model. This paper does not deal with the development of the southern California Borderland basins, but most of them apparently developed in about the middle Miocene (10 to 15 m.y.a.) (Blake and others, 1978) . According to Atwater, (1970) the migrating triple junction was in the vicinity of the Borderland in middle. Miocene time as well. Thus the southern California Borderland, while much more impressive in basin development than central California, does not offer the opportunity to distinguish between a migrating triple junction vs a mechanism involving near synchronous development of California offshore basins.

    ~To  investigate the possibility of    a change  in plate motions being responsible for the near synchronous development of the basins we reconstructed the history of Pacific-. America motion in much the same way as   Atwater and hiolnar (1973), and then computed average J-28

~, ~ movement vectors at 36'N, 121N, and 33 N, 119M for the intervals 0-4.5, 4.5-10, 10-21, 21-29, and 29-3S m.y. The results are shown in Table 1. Rotations were done in a reference frame fixed to North America and in a restorative sense for the global circuit Pacific-Antarctic-Indian-African-North American plates. Data sources are given in Table l. The thoro largest sources of error are in the central Indian Ocean (Ind-Afr) and the central Atlantic Ocean (Afr-NAm) because these rotations require 'the greatest amount of data interpolation of sea floor magnetic anomalies. Tectonic hind- . casting of this sort. can be improved upon only by more detail in those regions. In addition to the accelerated rate of movement in the late Cenozoic is the significant change of azimuth, especially after 21 m.y.a., 'or subsequent to the change along this continental margin from subduction to transform motion. At 36N, the azimuth is 339'or 21-10 m.y., 328'ox 4.5-10 m.y., and 321~ for 0-4.5 m.y.

                                  'I 4

These successively more westerly-directed movements of the Pacific relative to the North American plate may have produced extensional strain along the continental margin, perhaps culminating in the - middle Miocene, about 10-14 m.y.a. The extensional, strain was manifested in the formation of the basins along the Central California margin, and perhaps those of the southern California borderland as well. Since the vectors are computed from finite rotation poles they represent an average value for the time period, but not necessarily the actual direction at any specific time. If it were possible to J-29

                                                                      \ 'q  i ~

30 compute rotation poles for small time intervals we might discover that the pole of rotation between the Pacific and North American plates has been changing continually during the last 30 m.y. Such small but continual changes in direction and rate of plate move-ments may result in the development of a,complex structural geometry in the area of the plate boundary, as observed along Central California continental margin, and in fact, along the

            /

entire western margin of the United States. CONCLUSIONS Marine geological and geophysical observations support the general model of Atwater (1970) of early Tertiary subduction

                                     \

followed by Neogene translational shear along the Central California continental margin. Early Tertiary rocks form irregular structural I, surfaces and show relative1y intense deformation. Neogene strata are well layered, mildly warped and cut by high angle faults. Large shelf basins formed along the margin in late middle Miocene time, probably from a component of extensional strain during plate translational movements. Plate tectonic analysis using finite rotations around a global circuit: Pac-Ant-Ind-Afr-NAM, shows a change in average Pac-NAM movement during about middle Miocene to a more extensional sense of shear. This change could be responsible for the synchronous opening of the basins. This analysis shows a change in pole of relative movement for each 8 interval, and suggests that instantaneous movement between the Pacific and North American plates may have changed continually over the past 30 m.y. 1

31 Study of the continental margin provides constraints on thc-offset history of the San Andreas fault system. The northward extent of gr'anitic basement of the Salinian block, as traced by the Farallon ridge, limits basement offset to between 550 and 600 km. Of this figure, 300 km occurred on the San Andreas fault in Neogene time between San Francisco and the Transverse ridges and up to 150 km on the San Gregorio-Hosgri fault and the Rinconada fault south of San Francisco. These values add to the San Andreas offset north of San Francisco. Early Tertiary paleogeographic and provenance studies by Nilsen and Clarke (1975), as well as the difference between measured fault slip and basement offset are best explained if some offset on faults within the Salinian block occurred during latest Cretaceous to Paleocene time. Thus a two-stage, multifault model for Salinian offset is preferred,. with about 100 km slip in latest Cretaceous to Paleocene and about 450 km post-22 m.y.

    ,Granitic boulders dredged from Santa Lucia bank have two possible origins. Xf the boulders were locally derived,.granitic fault slivers must occur west of the Salinian block and the simple offset model presently accepted by many California geologists must be revised. Alternatively, the boulders may have been transported 100 km or more from source areas in the Salinian block.

                                                                               'C ~ '
                        ~   .
                                            'I Table 1.         Pacific-North America Finite Motions*

36~N, 121 O' 33'N, 119 W Time Interval Rate Hate m.y. Azimuth (1) (cm/yr) Azimuth (1) (cm/yr ) (2) 4. 5-0 321 5.6 319 5.6 (3) 10-4. 5 328 4.5 326 4.6 (4) 21. 2-10 339 3.2 335 3.1 (4) 29. 2-21. 2 32'1 3.8 319 3.9 (4) 38-29. 2 320 1.7 318 1.8

• Summation of the circuit: Pacific-Antarctic-Xndian-African-North American plates.

(1) Degrees positive clockwise from. north. (2) All rotations from Minster and others (1974) . All others

          'II (3) Pac-Ant from, Molnar and           others (1975)   .                from Minster and others (1974) .

(4) Pac-Ant: Molnar and others (1975) . Ant-Xnd: Weissel and oQ>ers (1972) . Xnd-Afr: McKenzie and,Sclater (1971) . A fr-NAm:, Pi tman and Talwani (19 72) .

I

~ ~

32 REFERENCES CITED Atwater, T. M., 1970, Implications of plate tectonics for the Cenozoic tectonic evolution of western North America: Geol. Soc. America Bull., v. 81, p. 3513-3536. Atwater, T. M. and Molnar, P., 1973, Relative motion of the Pacific and North American plates deduced from sea floor spreading in the Atlantic, Indian and South Pacific oceans: Kovach, R. L. and Nur, A., eds., Stanford University Publica-tions in Geol. Sciences, v. 13, p. 136-148. Bailey, E. H., Irwin, W. P., and Jones, D. L., 1964, Franciscan and related rocks, and their significance in the geology of western California: Calif. Div. of Mines and Geology Bull. 183, 177 p. Beutner, E. C. and Hansen, E., 1975, Structural evidence of plate interactions from continental rocks, Cape Mendocino to Shelter Cove, Cali fornia (abs. ): Geol. Soc. Amer. Abs. with Programs,

v. 7, no. 7, p. 997.

Blake, M. C., Jr., Campbell, R. H., Dibblee, T. W., Jr., Howell, D. G., Nilsen, T. H., Normark, W. R., Vedder, J. G., and Silver, E. A., 1978, Neogene basin formation and hydrocarbon accumulation in relation to the plate tectonic evolution of the San Andreas fault system, California: Am. Assoc. Petroleum Geol. Bull. (in pxess) . Buchanan-Banks, J. M., Pampeyan, E. H., Wagner, H. C., and McCulloch, D. S., 1978, Preliminary map showing recency of faulting in coastal south-central California: ,U. S. Geol. Survey Misc. Field Studies Map MF-910, 3 maps at 1:250,000.

Byerly, P., 1930, The California earthquake of November 4, 1927: Seismol. Soc. America Bull., v. 20, p. S3-66. Crowell, J. C., 1962, Displacement along th'e San Andreas fault; Cali fornia: Geol. Soc. America Spec. Paper 71, 61 p. Curray, J. R. and Nason, R. D., 1967, The San Andreas fault north of Point Arena, California: Geol. Soc. America Bull., v. 78,

p. 413-418.

Curray, J. R., and Silver, E. A., 1971, Structure of the continental margin and distribution of basement rock types of central California (abs.): Geol. Soc. Amer. Abs. with Programs, v. 3, no. 2, p. 106-107. Gawthrop, W. H., 1977, Seismicity of central coastal California (abs): Geol. Soc. America Abs. with Programs, v. 9, no. 4,

p. 422.

Graham, S. A., 1976,. Tertiary sedimentary tectonics of the central Salinian block of California: Ph.D. thesis, Stanford Univ., 510 p. Graham, S. A. and Dickinson, W. R., 1978, Evidence for 115 km of right slip on the San Gregorio-Hosgri fault trend: Science,

v. 199, p. 179-181.

Greene, H. G., 1970, Geology of southern Monterey Bay and its relationship to the ground water basin and salt water intrusion: U. S. Geol. Survey open file report, 50 p. Greene, H. G., Lee, W. H. K.', NcCulloch, 'D. S. and Brabb, E. E., II 1973, Faults and earthquakes in the h1onteroy Bay region, California: hiisc. Field Studies llap NP-518. J-34

~ ~ Hamilton, N., 1969, Mesozoic California and the underflow of Pacific mantle: Geol. Soc. America Bull., v. 80, p. 2409-2430. FFall, C. A., Jr., 1975, San Simeon-EJosgri fault system, coastal California: economic and environmental implications: Science,

       -v. 190, p. 1291-1294.

Hanna, G. D., 1952, Geology of the continental slope off central California: Calif. Acad. Sci. Proc., Fourth Ser., v. 27,

p. 325-358.

Hopson, C. A., Frano, C. J., Pessagno, E., and Mattinson, J. M., 1973, Late Jurassic ophiolite at Point Sal, Santa Barbara County, California (abs): Geol. Soc. America Abs. with Programs, v. 5, no. 1, p. 58. Hoskins, E. G. and Griffiths, J. R., 1971, FFydrocarbon potential of northern and central California off hore: Am. Assoc. Petroleum Geol. Mem. 15, v. 1, p. 212-'228. Hsu, K. J., 1971, Franci can melanges as .a model for eugeo-synclinal sedimentation- and underthrusting tectonics: Jour. Geophys. Res., v. 76, p. 1162-1170. Huffman, 0. F., 1972, Lateral displacement of upper Miocene rocks and the Neogene history of offset along the San Andreas fault in central California: Geol. Soc. America Bull., v. 83,

p. 2913-2946.

John on, J. D., and Normark, N. R., 1974, Neogene tectonic evolu-tion of the Salinian block, west-central California: Geology,

v. 2, p. 11-14.

Kulm, L. D., von Huene, R., and others, 1973, Initial Reports of the Deep Sea Drilling Project, v. 18, 1077 p. J-35

                                                                      ~ ~

Lawson, A. C., 1908, The California earthquake of April 18, 1906: Report o f the S tate Earthquake Investigation Commission,

v. 1, 451 p.

Martin, B. D. and Emery, K. O. ( 1967, Geology of Monterey Canyon, Cali fornia: Am. Assoc. Petroleum Geologists Bull., v 51( p 2281 2304 ~ Matthews, V., XXX, 1976, Correlation of Pinnacles and Neenach volcanic formations and their bearing on the San Andreas fault problem: Am. Assoc. Petroleum Geologists Bull., v. 60,

p. 2128-2141.'

McCulloch, D. S., Clarke, S. H., Jr., Field, M. E., Scott, E. N., and Utter, P. M., 1977, A summary report on the regional geology, petroleum potential, and environmental geology of the southern proposed lease sale 53, central and northern California outer continental shelf: U. S. Geological Survey Open File Rept. 77-593, 56 p. McKenzie, D. P. and Morgan, N. J., 1969, The evolution of triple junctions: Nature, v. 224, p. 125-133. McKenzie, D. P. and Sclater, J. G., 1971, The evolution of the Xndian Ocean since the late Cretaceous: Geophys. Jour. Roy. Astro. Soc., v. 25( p 437 528. Minster, J. B., Jordan, T. H., Molnar, P., and Haines, E., 1974, Numerical modeling of instantaneous plate tectonics: Geophys. Jour. Roy. Astro. Soc., v. 36, p. 541-576. J-36

Molnar, P., Atwater, T. M., Mammerickx, J., and Smith, S. M. I

                                                       'I 1975, Magnotic anomalies,       bathymetry, 'and the tectonic evolu-tion of the     South  Pacific since the late Cretaceous:                    Geophys.

Jour. Roy. Astro. Soc., v. 40, p. 383-420. Nason, R. D., 1968, Geology of Cape Mendocino, Dickinson, N. R. and Grantz, A., eds., Stanford University Publications in Geol. Sciences, v. 11, p. 231-34. Nilson, T. H. and Clarke, S. H., Jr., 1975, Sedimentation and tectonics in the early Tertiary continental borderland of central California: U.S. Geol. Survey Prof. Paper 925, 64 p. Page, B. M., 1970, Sur-Nacimiento fault zone in California: Continental margin tectonics: Geol. Soc. America Bull., v. 81I

p. 667-690.

Pitman, N. C. and Talwani, M., 1972, Sea-floor spreading in the North Atlantic: Geol. Soc. America Bull., v. 83, p. 619-646. Ross, D. C., 1972, Petrographic and chemical reconnaissance study of some granitic and gneissic rocks near the San Andreas-fault from Bodega Head to Cajon Pass, California: U. S. Geol. Survey Prof. Paper 698, 92 p. Seeber, L., Barazangi, M., and Nowroozi, A. A., 1970, seismicity and tectonics of coastal northern Micro-'arthquake California: Seismol. Soc. America Bull., v. 60, p. 1669-1699. Silver, E. A., 1974, Structural interpretation from free-air

                                                          /

gravity on the California continental margin, 35'o 40'N (abs): Geol. Soc. America Abs. with Programs, v. 6, no. 3, p. 253. J-37

Silver, E. A., Curray, J. R., and Cooper, A. K., 1971, Tectonic development of the continental margin off central California:

  . in Lipps, J. and Moores, E. M., eds., Geologic guide to the northern Coast Ranges-Point Reyes region, California: Guide-book, Geol. Soc. Sacramento Ann. Field Trip, p. 1-10.

I Suppe, J., 1970, Offset of Late Mesozoic basement terranes by the I San Andreas fault sys tern: Geol. Soc. America Bull., v. 81,

p. 3253-3258.

Uchupi, E. and Emery, K. O., 1963, The continental slope between San Francisco, Californi'a, and Cedros Xs., Mexico: Deep-Sea Res., v. 10, p. 397-447. Nagner, H. C., 1974, Marine geology between Cape San Martin and Pt. Sal, south-central California offshore: U. S. Geol. Survey Open File Report 74-252, 17 p. Neissel, J. K. and Hayes, D. E., 1972, Magnetic anomalies in the Southeast Xndian Ocean: Antarctic Oceanology XX: The Australian-New Zealand sector, Hayes, D. E., ed., American Geophysical Union, Nashington, D.C., p. 165-196. Nentworth, C. M., 1968, Upper Cretaceous and lower Tertiary strata near Gualala, California, and inferred large right slip on the San Andreas fault: in Dickinson, N. R. and Grantz, A., eds., Proc. Conf. Geol. Problems of the San Andreas fault system: Stanford Univ. Publications in Geol. Sciences, v. 11, p. 130-143.'oodring, N. P. and Bramlette i M N i 1950, Geology and paleontology of the Santa Maria district, California: U. S. Geol. Survey Prof. Paper 222, 185 p. J-38

FIGURE CAPTIONS Figure l. Track of geophysical cruises and geologic sample loca-tions on the central California continental margin. Heavy lines are seismic profiles illustratedin this paper. Identification of seismic profiles by cruise: W = Thomas Wa hington K = Kelez S = Bartlett 1972, leg 1

        .L =   Bartlett  1972, leg  2 LDM =  Davis  profile Identification of     samples by   cruise:

D = Kelez Dredge F = Kelez Dart Cores ADC = Melville (Antipode) Dart Core AD = Melville (Antipode) Dredge 7DS = Thomas Washington DartCore (7 Tow) B = Bartlett Dredge Figure 2. Map of structural features on the central California continental margin. Location of ridges, basins and major faults. CM: Cape Mendocino; PA: Point Arena; PR: Point Reyes; SF: San Francisco; M: Monterey; SS: San Simeon; PS: Point Sal; PC: Point. Conception. Figure 3. Map of faults and folds on the continental margin. Figure 4. Line drawing interpretation of Bartlett seismic reflection profiles L16 to L20 across the Santa Maria basin. J-39

Figure 5. Line drawing interpretation of Bartlett seismic reflec-tion profiles L2 to L14 across the Sur and Santa Maria basin. Figure 6. Free-air gravity map of the continental margin, from 35'o 40'North. Contoured from National Ocean Suryey unpublished data. Contour interval 10 mgal. Figure 7. Residual magnetic map of the continental margin and oceanic crust to the west. Map is combined National Ocean Survey data and Bartlett data. Figure 8. Crustal model satisfying observed gravity for profile L18. 2.65 means 2.65 gm/cc. No scale exaggeration. East is on the right. Figure 9. Reflection profile taken by D. G. Moore across the I Santa Maria basin showing local folding of strata against a "buttress" of acoustic basement. Labeled LDM on Figure 1. Figure 10. Line drawing interpretation of Thomas Washington profiles W6, 8, ll, 12, 13, 16, 18, 19, and 23. From Expedition 7-Tow, leg 9B. Figure 11. Line drawing interpretation of reflection profiles Kl, 3, 44, 66, 68, and 93, from the R/V Kelez. Figure 12. Line drawing interpretation of 'reflection profiles Sl-S4, from leg 1 of R/V Bartlett in 1972. Profiles cross outer Santa Cruz basin and Santa Cruz high. Figure 13. Line drawing interpretation of profile NX, taken along'he axis of Oconostota Ridge. J-40

~ ~ ~ Figure 14. Geometry of hypothetical stable and unstable fault-fault-trench triple junctions, predicted new condition of stability and generalized observed geometry. a) Stable fault-fault-trench triple junction. b) Generalized unstable form of Mendocino triple junction. c) Predicted new position of stability = Ridge-Ridge-Ridge

             .triple junction (this solution is from Clement Chas'e, Univ. of Minnesota,    oral    ,commun.,  1976).

d) General observed geometry of Mendocino triple junction, illustrating bending of San Andreas fault at its northern end, rather than triple junction evolution, to maintain gross geometric stability.

K sr ar SS~ Iti~ P a

                  ~a                                                                                                f 0                                            ~h, a, ae a0        +o a              0 a
                                                                 ~

4'I Oz

                                                                                               ,/
                                                                                               'J ap    SS
          /

g /Vlx A

                                                               ~

V o~+ 0, a

                                                                                                                                '1 Oc.

LI So

                                                  ~  0 y a         a   a.                  I ea ee V              CEOKKTSICAL TRACK IOO 0                       >SS 0    OREOCC OR    DART CCRC K<LOU ET E RS         IW KILCKCTERS                                   CONTOUR INTERVAL SOOIICTCRS SS          sr as.                  Sr                                                  SSilt V

l23~ Granitic ridge 40' 22~ 39~ l 2'8'7 20'6'5~ l Franciscan ridge 34~

                                                                                                                                                    ~ +

Basin ptl,tt'0 Fault . CALASERA9 B'AV

                                                             ~,'qu;Anp  ~t-QA l25~

Pr. Arrno 80$ cn iC

                                                 $ AV " '- "
                                                                   ~      "AN GRINGO:       J, R:0 FAV '.FA SVR .,;,;-. ~         hp9GRI FAV 7                                 I 200
                                                                                                     ~z~~zr/A... -~:;;:       ';.*.~ ZZ~
                                                                                                                                                       ~ ~ ~ ~ ~ ~

BASE 4 ~ ~ OF CONTINENTAL '.."-""" LOPE

                                                                                                                                          ~ ~ ~ ~ ~

l 2P tppKitomoters 40+ 39~ 38~ l25~ 37~ l24>> 36~ 35 l2 3'4~ l22~

It 5 ~ 50 ST+ SV 55>> TAULT, NACNUNCS OH OONNTHAOWM STOC fAULT TONIC

                                                                       -C-     AHTICLIAC 01 SASS@TNT 1ICCC STNCLINC   01 ~ ATIN ATIS X  XX   VOLCAN>C 1IOCC fAULT AHO C LA"<<AS                    5 All NAVSAAO TAULT l                                                                                                                 AINCO<AOA TAU'T 4

CCyo AII &oem

                         +f Aifat OASNI                       fAULT     ~  0        f                                                            TAULT  ~

pie SAAI ANOACAS P

                                     ~I
                                                             ~
                                                                                     ~ P~

O OCO+OSTOTA ALCOO

                                                           ~ N f4'              ,c.'--  ~

lll15( SA>>N

                          '5 INLN SLOrC                                          CAVC
                                                                                                                  +

UOA ~ ~ <11 CON ,~ SAIITA TOUT Igg S SASC 55 It5'5 0 X ILOIICT 5 15 IOO 55 ITS 55 Ri Itt

t40 120 80 40 20 Km 0

                                                                                 ~ 0 Santo Lucia Sonto   ferro  Basrn Bank                                                    Sec    L16 C
                                                ./. KP
                 /              rr                         20      Km     0 6                                           0 a

CZ lal

                                                                            <<c L18 k .~~~/r 20      Krn     0 0

s<<L20 rr ~r+ i/ +r F~- / wr 20 Krn 0 0

         ~r r
       /q                          ~ci$:" 'r     "=--.    =;-'==--.=-~~.Q/       i      ~     Sec Fcurt 20      Km       0 gr Q Sec   L24 r/          05 M VQ~~               s<<L26 20    Km    0 0 2
                                                                              <<c     L28 07 Santa Bank Fault V,Kp 10K

                                                                                    ~ ~

40 20,Km 0 0 Sec Km 0

                   ~ r/       Cr ~

2 0 p. r/ Sec L4 r 20 Km 0 0 I Sur Basin Sec L6 ig f/ r,rr 20 Km 0 0 sc Lg cS'r r 20 Km 0 p gr Sec L.10 2 ri 20 Km 0 0 c' 20 Km 0 s cocc 8 K

                                   . s  c   Mo. pc~   jP.

0 2 rrSrr V.E.~ 10K

~ o J-46

c c )pc I25' 1r 4c 123'22c 4ac O O 0 30c 38c Bodega Head I 0 0 r Pt. Reyes 38'7 San Francis 38'-'

                                               "    C 'c
                                                              >  Pt. Ano Nuevo
        ~

121'7c 125c 70 oo ~

                                                                 ~    .p(( ..
                                                                       "".. Monterey Point Sur rc~~c~     '-+yy 38c 0             50 KM Interval 10 mpal FREE-AIR GRAVITY                                                      ~Ecrcrc Bay 4@~

35'24 c 123c 122c 35'21'-47

4 pe 12S 123 t

                                               ~                 122'200                                          400 I ~ ~

MAGNETIC ANOMALY (') I MEANS IOO nT (gommos) CONTOUR INTERVAL:100 nT Q INACTIVE TRARSFOIIM FAULT

       'I m,MQ I    0 FT ARCNA BASK OF CONTINEtlTAL SLOPE
                                                                        . UNCONTOURED tlAGNKTIC HIGH MAJOR FAULTS V
                                           ~ ODCCA g, g 3t)0
                                       ~+               5AN FRANCISCO               0 N)LOMCTCN5
                                                                 .5AN)A CRV?

370 MCNTCRCT ~ 01

                                                                    ~ AT 36'.Cg                  0                            II
                                                        /

NONTCIICT I I I Co 0 0

                       +0 0

36'5' C3 CVCNON

                  /                                                    Q
                                                                                     )

(.) J 0

                                                                   /                                               350
                                                                                                    ~ T, 5AC I

I'. ANCVCLL 0 .I -. 34'250 0 Yn 124 1230 J-,48

F R EE-AIR GRAYITY 0- 0 Q~m~ 4 m gal -IOO-CALC. Santa Lucia Bank 2.2 2.2 50 I 0 I 0 0 I.03 KM 2. 85 2.6 5 IO 20 3.2 7 3.0 3.23

500

                           )000 6 Vertjoai Exaggeration: X IO

, ~ ~ ~ ~ ~ I E 0 s~ W6

                                                                          ~SW 0

sgf , ~l. sec WB Cger.' A022 .~- '.J.<'nl

                                             ~ e 0

0

                                           ~*';~OJj~                     .          V/11 s
                        ~J J

J J r Knl 0 0

                                                 ~==;.-0 Km            0 0

r sec W16 r/g~r

                      .r+Zi" 0

C J s W18 0 sec W19 Sodege Oosel Km 2 0 Forooon sec W23 J

                                            .J).j V F.ecsx 2

o 2

4 X0+3A r V.

                                                                                                                                        '5uovo 51015 1 0 ivO t vOH r7
 ~,          I 01            OC
                           ~ 5uo41 o!555 tuivut'10l5 OC        or r

CO

                                                                                          ~

4e

                                                        ~

01 OF

                                                                                                            ~r 55vov> o oo5                                           jv'9M 101vut   Alp
       ~s
          ,!,:.~j~"=..':-~.

01 OC OC OF 00 F'SC O5v001 O;075 ,r lO'I votuCH 51>)l 1 <c IJ 05 Or 00 00 d~r'. r rK

                                                                                                                        >r yr
                                                                                                                  $ r 5                             Or       rrv tv~   ukDQ o5opoQ SP 01       OZ          CC ~           Or          00           00         01 CO            05

e 80 = 40 20 Km 0. 0 Sec 5$ Pioneer Seamount 4+ r'0 4 fe Forollon Ridge 20 Km 0

           ~~~~~/r  ~~4                    Outcr Sonta Cruz
                                                                             ~f  MY; 0

Sec $Q 20 Km 0 0 Santa Cruz High

                                          ,i Guide Seamount l
                                                                                                   'Km
                                                                                                     \ d
                                                                                            ~        ~   ~
                                      ~Pl V.Ep 6X rP

e. '~ r--.-

                ~A

KILOMETERS 80 70 60 50 40 20 IO 0 IO 2000 3 CL-O O 1JJ 300 40

                       ~                             0 Stability Considerations of              a  FFT Triple Junction

0) Stable FFT 8} Unst'able FFT America , America )GA I

Gorda Gorda Pl PG G l Pacific Velocity Pacific I Triangle Al I lGW C) New Stability Condition D} Mendocino FFT after (D) RRR Triple Junction America PG Gorda P America PA yl A Pacific 'Pacific PA means Paci f ic- Anterica P l a te Boundar y plotted on velocity'riangle J-55

N

             ~   ~
         ~     '   ~ ~      ~

I ~

                                                               ~                                                         ~

App chica'".ion of Itnear s'Latts'Ltcal mociels of ear&quake magnitucxe

      ~
      ~
       ~  4
             ~
             ~

versus fault. Iengt>t tn esct!TlaLtng rnaxImu~~ e;,pec'cable earthquaI:es

           ~
     ~

0

   ~     ir
       ~ ~

r Robert >x Marl r

   ~   Nr r                                                                                                                                                 '.S. Geological Surve
     '\

r~ ~ Menl, Park, California

       ~r
    ~,'l                                                                                                                                                                           940"';

C ~

   ~; 1 r

C'OD ABSTRACT lOOO Correlation or linear rcgrcssion estimates of earthquai;c magnitude from data on liistorical magnitude and length of sur-

                      'ace rupture should bc based upon the correct regression. I'or example, thc regression of magnitude on thc logarithm of thc length of surface nipturc L can be used to estimate magnitude, but thc recession of log L on magnitude cannot. Rc~ccssiott cstimatcs arc most proliable values, and estimates of tnaximum values require consideration of onewided confidence limits.

INTRODUCHION In estimating maximum expectable carthquakcs, it is common ce practice to assume a paximum length of surface rupture (typically onc-half the fault length) and use "lines of best fit" to cstimatc CJ

    ~~

maximuin magnitude front graphs comparing historical carth- C'> quakc magnitudes and lcrgtlis of associated surface ruptiircs. This note discusses thc intcrprctatinn and use of linear regression or I ~ ~ correlation models for niaking statistical inferences from data r. io ~ r r~ events. Fnr cxamplc, DnniDa and Duchanan (1970) re- on'istorical

                                                                                                                                        >J ported length of surface rupture L and Richter magnitude hf for those earthquakes for svhieh these data v:erc available and prc-                                           iO e8 scntcd "best fit" equations of thc form lng L a+ bhf, that is,                                           e>  p thc linear regressinns of log L nn magnitude (Fig. 1. linc AA').

ct Othei authors (fnr exani pie, Tocher, 195S; lido, 1965) liavc calcu-lated rcgrcssinns of ma<!iiiludc nn log L (Fig. 1, lines DD'nd CC'). I will argue that all these rel!ressinn lines have bccn used ilt-corrcctly to cstiinate niaxinium earthquake magnitudes from maximum ruplurclenglhs a.'nng foul!s. That is, th" v:rorg regres- r a As ~ Ds 0 ec 4 sion linc (lng L on inagnitudc) has been used to cstimatc niagnitudc t:ARTHQV/AE use>r'>TUBE from niaximum rupture )englli, or regression estimates have been interpretetl as maximuin ralher then ninct likely mal!niluilcs (fnr 1'igurc l. I.engih nf nt>se>ved sn>bee inpiuie in ictstiin> In esiih. quake n>a::nilude. l.ine *A is s iegiession line nf lng l. on >n.>dniin>.c. cxaniplc, Greene anil nlhers, 1973; 5'entwnrth and nlhers, 1973; Lines till, CC', and till'ic >cpa ssi>>n tines ur iuagniiude un t>>gr J.. l.in KYesson and nthers, 1974. 1975). AA'nd I)t)'ic based un ihe s>>nc data. GCOLOGY, v. 6, p. dG4-4GG, AUGUST, t'ai K-1

.r I tW A CORRELATION MODEL It is possible to use thc statistical model to estimate thc mag-nitude, as a function of length, that could bc cxpccted to be cx-Many models can be used to draw statistical inferences from cccdcd in a given proportion (1 - cc} of surface-rupture occurrences. thc data on magnitude and lcng(h of rupture. A transformation to using a onc-sided confidence limit (IVonnacott and IVonnacott, log I. is used bccausc it tends to nornulizc thc data and to cn- 1972, p. 280): hancc thc linear relationship. For thc purpose of this discussion, a (log L - fcfrr,(L) = il f(L) + l t la~7.)'I-+ corrchtion model is postulated in which it is assumed that n cx, s I + magnitude versus log L data points arc ranclocnly drawn from the 5 (log Ll - logZ)~ l~t population of carthquakcs 1vith associated surface rupture and that such a population has a bivariatc norcnal distribution (Fig. 2). where M(L}is the rcgrcssion value, r,.o, is thc critical value of thc As indicated b low. these assumptions arc morc rcstrictivc than l distribution cvith (n - 2} degrees of frccdom, s is thc standard necessary. As shown in Figurc 2, thc rcgrcssion linc ol'on X, or error of thc rcgrcssion, Ll is thc rupture Icnl<h of thc ith carth-Y ~ a + 1}X, passes through thc most probable value of Y for quakc occurrence in the sample of n earthquakes, and log L is thc each X and is thc appropriate linc to cstimatc Y given X. The mean of log L. That is, thc curve i'Vx(L) is thc locus of points such other regression linc, thc rcgrcssion of X on Y, passes through thc that for a particular L. I - cc is thc probability that the magni-most probable value of X for each Y and will not provide an tude will cxcced hQ. Note that the regression linc M(L) is equiva-unbiased estimate of Y given X. Thus. thc line of Bonilla and lent to M,.,(L}. Buchanan (1970} in Figurc 1 is not the correct regression line for As an cxamplc, Bonnilla and Buchanan (1970) reported data estimating earthquake magnitude from fault length. Itather, thc on strike.slip faults (n ~ 20) and calculated the rcgrcssioa linc appropriate regression of magnitude on log L, calculated using (L in mctrcs} their strike-slip fault data, is liuc DD'Fig. 1). It is similar to thc 'og L ~ 1.915+ 0.389M, r ~ 0.70, s ~ Q.S2. equivalent regression lines of thc other authors. The regression of M on log L }acids M ~ 1.235 + 1.2 13 log L. r ~ 0.70, s ~ 0.93. These lines arc plotted in Figurc 3, along with tho data points. ESTIV)ATION OF MAXIMUM Also plotted arc the curves hf>.>> and M, >> lor thc regression of EARTHQUAYMMAGNITUDES M on log L..A magnitude value from the rcgrcssion linc 'f(L) can Thc regression lines of rnagnitudc on log L can bc used to bc rcfcrred to as the most likely m..gnitude for a given rupture estimate thc most likely rnagnitudc for a given maximum rupture. length, and a value from hfJL) as a maximum cxpcctablc carth-It must bc stressed that such an estimate is riot a maximum mag- quakc magnitude at cxcccd*nce probability' cc. nitude, but rather thc magnitude that could bc expected to be Thc line EE'n Figurc 3 cocmects the points that form the exceeded in 50% of thc earthquakes associated with that rupture right.side cnvelopc of the data. This field lies cntircly to the left length. of Mo>>, and on thc basis of thc model. there are potential cvcnts larger than EE'hat have probabilities in excess of 5%. Thc prcccding numerical results are somewhat model dcpcnd-cnt, in that they dcpcnd on the population distribution and sscnple selection, but thc genera) hnplications have wide application. Estimates of most likely earthquake magnitudes for a given value of an "indcpcndent variable" (such as rupture length or fault displacement) must be based on thc correct rcgrcssion, and esti-mates of "maximum magnitude" rcquirc consideration of the distribution about thc regression linc and thc application of onc-sidcd confidence limits. These results can also bc derived from a less restrictive linear tcgrcssion model in which log L is treated as an independent vari-able and M is assumed to bc normally distributed about thc rcgrcssion li>>e (Af on log L) with variance indcpcndcnt of L (Hays, 1973, chap. IS). ll'he data warrant, thcsc models could be ex-panded to include additional "independent variables" such as x= ccrc gg tectonic setting ancl hypoc.cntral depth. A statistical approach is also nccdcd to csticnatc thc maximunt surlacc rupture (at some 0 Px cxcccdance probability) for a given total fault length. Flcclcc 2,'Yhc tcvo ccyccs)loll thws ic) 0 t)lvaliatc llocmat pop))tattoo, c contoc) cz indicate c teal pc))t at)ility density, ~t)))tificd frocu 4'vc)c)acutt xcecdance pcobability is the probability that somcthi))t., in this and 4ocmacoct t t97)). case mat.nitudc, v ctt t)c cxcccdcd. GP.OLOGY K-2

Don)()a, hl. G., and Buchanan, J. I'l., 1970. Interim rcport on tvorld svidc historic surface faulting: U.S. Geol. Survey Open File l(ep(., 32 p. Grccnc, SV. H., I.ec, W.l). IL, hlcColloclh IL S., and Brabb, )L I 1973. I'aults and earthquakes in thc htontcrey Day region, California: U.S. Geol. Survey text tn accompany map MF 518, 14 p.

                                                                                  )lays, W. L., ) 973, Statis(ics for thc social scicncesr Ncsv York,)lolt.

Rinehart, and Winctnn, 954 p. lida, Numizi, 196S, I'.arthquakc magni(ude, earthquake fault and source dirncnsions: Nagnya Univ. Jour. Forth Sci., v. )3, p. I I 5~)32. Tochcr, Don, 1958, Lsar(l>qua),"e energy and ground breakage( Seismol. Soc. America Bull., v. 48. p. 147-) 53. Q Wcsson, R. L., I'agc, R. A., Boore, D. hl., and Yerkcs, R. I'., 1974, Isx. I )30 pcctable carthquakcs in thc Van No(roan Reservoirs area: U.S. Geol. Survey Circ. 69)-B, 9 p. Wcsson, R. L., )le)Icy, E. J., La joie, K. R., and Wcnttvorth, C. M., 1975, Faults and future earthquakes, fn Irorcherdt. R. D., cd., Studies for seismic zonation of thc San Francisco flay region: U.S. Geol. Survey Prof. Paper 9C I-A, p. AS-A30. Wenhvorth, C. h'l., Beni))a, M. G., and Buch nan, J. hl., 1973, Seismic h~ environment of thc Burro Flats site, Ventura County. California( hs U.S Geol. Survry Open.File Rcpt.. 35 p. Wonnacott, Thorn..s H., and Wonnacott, Ronald J., 19'12, introductory statistics for business and economics: Ncsv York, Wiley, 622 p. R rg J(CIÃQAYLEDGMEHTS Rcvicwcd by D. R. Dasvdy, D. G. Ilcrd, R. A. Page. and D. hl. o Perl:ins. ls hlANUSCRIPT RECEIVED APRIL 27, 1977 v 4 MANUSCRIPT ACCEPTED MAY 3, 1977

                                      ~4 I

A 3 q 85 C 66 07 8 KARTHQVAN\ s(AH(TVDE Figurc 3. Length of obscrvcd surface rupturcvcrsus earthquake magnitude for thc strike slip fault da(a of llunith and Ltuchanan (1970). Linc AA's thc regression linc ol'ng 1. on macnitude aml could be used lo estimate thc ntost likely tuplurc length associated svith a given magni. tudc earthquake. I.inc IIps's the r ctu essiun line of magnitude on log I and c'ouid bc used to cstunate thc must likely earthquake tnagnitude associated with a riven lrngth of surface (upture. On thc basis oi'hc correlation rnnA I, half thc car thqua'kcs associated with a given length uf sur(acc rup(ure rouhl bc eapcctcii (u lsc larger than IIIJ . The marnitudcs 'given by linc Dl)'ou)J bc eapec(cd tn exceed 95%, of the a(agni(udes fur earthquakes assucia(ed with a given I; ngth of surface (up(urc. Thc linc EE's the ri).ht.sh(c envelope of observed data. K-3

                                                                        ~ WHlle IN vs a                                                               AUGUSi

ATTACHMENT L UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY REGRESSION ANALYSIS OF EARTHQUAKE MAGNITUDE AND SURFACE FAULT LENGTH USING THE 1970 DATA OF BONILLA AND BUCHANAN By R. K. Mark and M. G. Bonilla Prepared in cooperation with U, S. Nuclear Regulatory Commission. OPEN FILE REPORT 77-614 This report is preliminary and has not been edited or reviewed for conformity with Geological Survey standards and nomenclature. Menl o Park, Ca 1 i for ni a 1977

REGRESSIOH ANALYSIS OF EARTH(UAKE MAGNITUDE AHD SURFACE FAULT LENGTH, USING THE 1970 DATA OF BONILLA AND BUCHANAN By R. K. Hark and t1. G. Bonilla Introduction. The report of Bonilla and Buchanan (1970) includes re-gressions of fault length on earthquake magnitude that can be used to estimate most probable length of surface rupture given earthquake magni-tude. Those regressions, however, have sometimes been incorrectly used to estimate magnitude from fault length, as pointed out by Hark (1977). Using the data of Bonilla and'Buchanan, this report gives regressions of earthquake magnitude on length of surface rupture that can be correctly used to estimate most probable magnitude if the length of surface rupture is given. It also gives the regressions of length of rupture on magnitude that can be used to estimate most probable length of rupture given earth-quake magnitude. In table 1 and figures 1-5 the numbering and lettering system used to designate fault geography and fault types is the same as in Bonilla and Buchanan (1970). Numbers 1-49 include surface ruptures that occurred in North America and numbers 50-140 include ruptures outside of North America. The fault types are indicated by letters as follows: A, normal-slip faults; 8, reverse-slip faults; C, normal oblique-slip faults; 0, reverse oblique-slip faults; and E, strike-slip faults. Use of the re ression lines. The regression of log length on magnitude L-2

                    ~                                 ~

(Log L=a+bM) can be us<<d to estimate the most probable rupture length given magnitude, and the regression of magnitude on log length (M=a+b Log L) can be used to estimate the most probable magnitude given rupture length. The estimation of 'maximum magnitudes'or a given rupture length requires the use of one-sided confidence limits (Hark, 1977) . References cited Bonilla, H. G., and Buchanan, J. M., 1970, Interim report on world wide historic surface faulting: U.S. Geol. Survey open-file rept., 32 p ~ Mark, R. K., 1977, Application of linear statistical models of earthquake magnitude versus fault length in estimating maximum expectable Y. Sq p + ~ + + 6 b~ A UQ 0 s l. earthquakes: Geology,'A +a-p~. L-3

Table 1 Regression analysis of magnitude - surfac'e rupture length data from Bonilla and Buchanan (1970). f Log(L) =a+b~H N=a+b*Log(L) set n r~ a b s a b 1-49 20 0.3?2 10. 64. -0. 91 0. 35 0.51'.23 1.08 0.90 50-140 33 0.217 8. 57. -1.49 0.40 0.55 6.56 0.54 0.64 1-140 53 0.257 17.62 -0.96 0.34 0.53 6.03 0.76 0.80 14 0.175 2.55 -0.69 0.28 0.45 6.19 0.63 0.68 7 0.003 0.01 not significant 7 0.459 4.24 -2.81 0.61 0.38 6.08 0.75 0.42 5 0.006 0.02 not significant -E 20 0.484. 16.87 -1.08 0.39 0.52 4.96 1.24 0.93 A+C 21 0.279 7.37 -1.46 0.40 0.45 6.13 0.70 0.59 B+D 12 0.033 0.34 not significant C+D+E 32 0.367 17.42 -1.24 0.40 0.55 5.62 0. 93 0 84 12 0.'230 2.99 -2.79 0.59 0.57 6.62 0.39 0.47 B+E 27 0.299 10.65 -0. 71 0. 32 0.56 5.71 0.94 0.97 A+C+E 41 0.380 23.94 -1.20 0.39 0.49 5.56 0.99 0:79 B~D+E 32 0.251 10.07 -0.81 0.32 0.60 5.98 0.78 0.93 Notes "n" is the number of cases.

   "t  "  is the fraction of the variance explained by the regression.        It ranges   from 0 (no   linear relationship) to 1 (perfect linear relationship).
   "f" is   a  measure   of statistical significance of the regression    and is equal to r~/
  .((1-8 )(n-2)).
   "L" is in kilometers.
   "s" is the standard error of the estimate. s~ is equal to the residual sum of square errors about the regression line divided by the degrees of freedom (i.e., n-.2).

L-4

SICKO, 800

   '00 600 50Q 400 500 20Q 0

SORLDV/!DE DATA K ELJ IOO 0 90 hC 80 70 I-D 6o

u. 50 0 40 so D

I-20 O

b. IO 0 9 8

7 R ld 6 5 O h 0 O X + O tp

                 /0                   EO I/

O 0 0 5 t 9 EARTH'QUAKF MAGNITUOE F ip.l L-5

IOOO 800 eOO 700 600 500 400 300 200 M NORTH AMERICAN DATA LIJ I-IOO 0 90 80 hC 70 60 50 40 <<K QJ 30 IL I-LL. 20 K Lal O Io LL. 9 O 8 I- 7 Z 6 LLJ

                V~

Oa O o~ O 4Q 6 7' 9 EARTKQUAKE MAGNITUDE Fig.2 L-6

~  '(

9oo ~ 800 700 600 500 400 500 200 V) NORMAL-SLli~ FAULT DATA CL Lal le loo 0 90 80 70 I-Go 50 40 Z K so I-tL 20 u-, 0 lo 9 8 7 R 6 Cn 5 O 0

                                           +

Cb X 0 0' 5 6 EARTHQUAKE MAGNITUDE L-7 /)

IOOO eno 800 700 600 500 400 500 200 Vl ORBAL OBLI Q UE-SLt P FAULT DATA fL ld I-ion 0 90 80 70 I~ 60 U 50 R 40 lL so D I-0 20 O K D lo 0 9 I- 8 LU 5 O h O

                                            +

0 D CO II 5 6 EARTHQUAKE MAGNITUDE L-8

   .aoo 000 700 600 500 400 300 200 CO           STPiI ViE- SLIP    FAULT DATA LLI I-IOO O      90 bC 80 70 60 LL. 50 cf     40 0

LLJ 30 I-tL D 20 LLj CD tO LL lo O x I- 8 E9 7 z LLJ 6 5 Ch O o'.

          /j                   0) 5         6 EARTHQUAKE MAGNITUDE

I~

  ~    g '
                ~                                     BIOGRAPHICAL SKETCH                                      ATTACHMENT M (PROVIDE     FOLLOWING INFORh)ATION FOR ALL PROFESSION~RSONNEL ENGAG~      TIIE PROJECT, BEGINNING WITH THE PRINCIPAL ~TIGATOR.)

I NAME James N. Brune BIRTHDATE (MO., DAY, YR.) November 23, 1934 PLACE OF B(RTH PRESENT NATIONALITY (CITY, STATE, COUNTRY) (ALIENS INDICATE KINO OF VISA AND EXPIRATION DATE) Modesto, California U.S.A. U.S. Citizen EDUCATION (BEGIN WITH BACCALAUREATE TRAINING AND INCLUDE POSTDOCTORAL) DEGREE YEAR CONFERRED INSTITUTION AND LOCATION B.Sc. 1956 University of Nevada, Reno, Nevada Ph.D. 1961 Columbia University, New York City HONORS AND AWARDS See Attached MAJOR RESEARCH INTEREST Earthquake Source Mechanism Tectonics Earth Structure RESEARCH AND/OR PROFESSIONAL EXPERIENCE (STARTING WITH PRESENT POSITION, LIST PROFESSIONAL BACKGROUND AND Eh'IPLOYMENT) Professor oI Geophysics-University of California, San'Diego, 1969-Associate Director, Institute of Geophysics and Planetary Physics, University of California, San Diego, 1973 1976.. Chairman, Geological Research Division, Scripps Institution of Oceanography, University of California, San Diego, 1974 - 1976. Associate Professor of Geophysics-California Institute of Technology, 1965 - 1969. Adjunct Associate Professor of Geology-Columbia University, 1964. Geophysicist, U. S. Coast and Geodetic Survey, 1964. Research Scientist, Columbia University, 1958 - 1963. Research, Chevron Oil Company, 1957. 'xploration Exploration Geophysics, Chevron Oil Company, 1956.

UCSD-0071 James N. Brune .HONORS Higgins Fellowship, Columbia University, 1956 University Fellowship in Geophysics, Columbia University, 1957-58 i)ax Fleischr~~an Scholarship, University of Nevada, 1954-55 Jones-Hoover Scholarship, University of Nevada, one year J. B. HacIlwane Award of American Geophysical Union, 1962 Fellow of the American Geophysical Union, 1967 Grove Karl Gilbert Award in Seismic Geology, 1967 Seismol'ogical Society of America: Board of Directors, 1967-present, Yice-President, 1969, President, 1971 Meri>ber of New York Acaderi>y of Sciences, 1970 Arthur L. Day Award, 1972 G.. K. Gilbert Award, Carnegie Institution of Washington, 1967 Llstlngs in vho s vho in the vest, kne2ican Zen of science M-2

BIBLIOGRAPHY James N. Brune

l. (With J. Oliver) The Seismic Noise of the Earth's Surface, Bull. Seism.

Soc. Amez., 49: 4, 349-353 (1959). 2 ~ (With J. E. Nafe and J. E. Oliver) A Simplified Method for the Analysis and Synthesis of Dispersed Have Trains, Jour. Geophys. Res., 65: 1, 287-304 (1960). 3~ (With J. E. Nafe) Observations of Phase Velocity for Rayleigh Waves in the Period Range 100 to 400 Seconds, Bull. Seism. Soc. Amer., 50: 3, 427-439 (1960). 4~ Radiation Pattern of Rayleigh Waves from the Southeast Alaska Earthquake of 10 July 1958, Domin. Observ., 24, 20, A Symposium on Earthquake Mechanism, 1-11 (1961).

5. (With M. Ewing and J. Kuo) Group and Phase Velocities for Rayleigh Waves of Period Greater than 380 Seconds, Science, 133: 757 (1961).

6. (With J. E. Nafe and L. E. Alsop) The Polar Phase Shift of Surface Waves on a Sphere, BuZZ. Seism. Soc. Amer., 51: 247-257 (1961).

7. (With H. Benioff and M. Ewing) Long-period Surface Waves from the Chilean Earthquake of May 22, 1960, Recorded on Linear Strain Seismographs, Jouz.. Geophys. Res., 66: 9, 2895-2910 (1961).

8. Attenuation of Dispersed Wave Trains, BuZZ. Seism. Soc. Amer., 52:1, 109-112 (1962).

9. (With J. T. Kuo and M. Major) Rayleigh Wave Dispersion in the Pacific Ocean for the Period Range 20 to 140 Seconds, Bull. Seism. Soc. Amez'., 52:

27 333-357 (1962).

10. Correction of Initial Phase Measurements for 'the Southeast Alaska Earthquake of July 10, 1958, and for Certain Nuclear Explosions, Jouz. Geophys. Res.,

67: 9, 3643-3644 (1962).

11. (With M. Ewing and J. Kuo) Surface Wave Studies of the Pacific Crust and Mantle, Geog. Monograph, 6, Crust of the Pacific Basin, (1962).

12. (With J. Dorman) Seismic Waves and Earth Structure in the Canadian Shield, Bull. Seism. Soc. Amez., 53: 1, 167-209 (1963).

13. (With A. Espinosa and J. Oliver) Relative Excitation of Surface Haves by Earthquakes and Underground Explosions in the California-Nevada Region, Jour. Geophys. Bes., 68: ll, 3501-3513 (1963).

14. Use of Surface Have Rejection Filters to Record Mantle Haves of Low Order, "~-

Earthquake iVotes, 34: 73 (September December 1963). (Abstract) M-3

                                                                                 ~
                                                                                   ~

N. Brune Bibliog hy (With P. E/. Pomeroy) Surface Wave Radiation Patter'ns for Underground Nuclear Explosions and Small Magnitude Earthquakes, Jour. Geophys. Res., 68: 17, 5005-5028 (1963). Travel Times, Body Waves, and'Normal Modes of the Earth, Bull. Seism. Soc. Amer., 54: 6, 2099-2128 (1964). (With R. Chander) Radiation Pattern of Mantle Rayleigh Waves and the Source Mechanism of the Hindu Kush Earthquake of July 6, 1962, Bull. Seism. Soc. Amer., 55: 5, 805-819 (1965). (With L. E. Alsop) Observations of Free Oscillations Excited by a Deep Earthquake, Jour. Geophys. Res., 70: 24, 6165-6174 (1965). The Sa Phase from the Hindu Kush Earthquake of July 6, 1962, Pure and Applied Physics, 62: 3, 81-95 (1965). P and S Wave Travel Times and Spheroidal Normal Modes of a Homogeneous Sphere, Jour. Geophys. Res., 71: 12, 2959-2965 (1966). (With J. Oliver, A. Ryall and D. Slemmons) Micro-earthquake Activity Recorded by Portable Seismographs of High Sensitivity, Bull. Geol. Soc. of Amer., 56: 4, 899-924 (1966). (With R. C. Liebermann, C. Y. King and P. W. Pomeroy) Excitation of Surface Waves by 'the Underground Nuclear Explosion Long Shot, Jour. Geophys. Res., 71: 18, 4333-4339 (1966). F (With C. R. Allen) A Micro-earthquake Survey of the San Andreas Fault System in Southern California., Bull,. Seism. Soc. Amer., 57: 2, 277-296 (1967). (With C. R. Allen) A Low-stress-drop, Low-magnitude Earthquake with Surface Faulting: The Imperial, California, Earthquake of March 4, 1966, Bull. Seism. Soc. Amer., 57: 3, 501-514 (1967). (With M. Wyss) The Alaska Earthquake of 28 March 1964: A Complex Hultiple Rupture, Bull. Seism. Soc. Amer., 57: 5, 1017-1023 (1967). (With C: Y. King) Excitation of Mantle Rayleigh Waves of Period 100 Seconds as a Function of Magnitude, BulZ. Seism. Soc. Amer., 57: 6, 1355-1365 (1967). She FauR'Slips, Engineering and Science Magazine, California Institute of Technology, 31: 2, 36-38 (1967). Seismic Moment, Seismicity, and Rate of Slip along Major Fault Zones, Jour. Geophys. Res., 73: 2, 777-784 (1968). M-4

~      E   ~

ii James N. Brune - Bibliography

28. Source Dimensions of Earthquakes and Underground Explosions of Magnitude Near 4.0, Earthquake Notes, p.'22, (Abstract), June, 1969.

29. (Mith C. R. Allen, A. Grantz, M. M. Clark, R. V. Sharp, T, G. Theodore, E. M. Wolf and H. Myss), The Borrego Hountain, California, Earthquake of April 9, 1968: A Preliminary Report, Bull. Seism. Soc. Amer., 58: 3, 1183-1186 (1968).

30. (With H. Myss), Seismic Homent, Stress and Source Dimensions for Earthquakes in the California-Nevada Region, Jour. Geophys. Res., 73: 14, 4681-4694 (1968).

31. Regional Variations in the Structure of the Upper Mantle and the Propagation of the Sa Phase, Continental Margins and island Arcs, Upper Mantle Comiittee Symposium, Ottaua, Canada, -'965, GSC Paper 66-15, (1969).

32. Surface Maves and Crustal Structure, Geophysical rVonograph, 13: 230-242 (1969).

33 (With G. R. Engen), Excitation of Mantle Love Waves and Definition of Yiantle Wave Magnitude, Bull. Seism. Soc. Amer., 59: 2, 923-933 (1969). 33a. Seismicity, Rate of Slip, Stress and Heat Flow along the San Andreas Fault in California, EOS Trans. Amer. Geophys. Union, SO: 5, May 1969.

34. (With'T, Henyey and R. Roy), Heat, Flow, Stress and Rave of Slip Along the San Andreas Fault, California, Jour. Geophys. Res., 74: 15, 3821-3827 (1969).

I E

35. (With M. Thatcher), Higher Mode interference and Observed Anomalous Appa ent Love Wave Phase Velocities, Jour. Geophys. Res., 74: 27, 6603-6611 (1969).

36. (With H. Trifunac), Complexity of Energy Release During the 1'mperial Valley, California, Earthquake of 1940, Bull. Seism. Soc. Amer., 60: 1, 137-160 (1970).

37 ~ (With D. Anderson, C. Archambeau, C. Richter, S. Smith), Earthquakes and Nuclear Detonations, Science, 167: 1011-1012 (Feb. 13, 1970).

38. (With W. Arbasz and G. Engen), Locations of Small Earthquakes Near the Trifurcation of the San Jacinto Fault Southeast of Anza, California, Bull.

Seism. Soc. Amer., 60: 2, 617-627 (1970).

39. Tectonic Stress and the Spectra of Seismic Shear Waves from Earthquakes, Jour. Geophys. Res., 75: 26, 4997-5009 (1970).

40. Seismic Sources, Fault Plane Studies and Tectonics, EOS, 52: 5, 178-187, Hay 1971, (IUGG Quadrennial Report'n Seismology for U.S.)

ames N. Brune - Bibliography PD'VI'a (with flayne Thatcher) "Seismic Study of an Oceanic Ridge Earthquake.

Swarm in the Gulf of California'eophps. Z. p. as0z'. Soc., 22: 473-489 (July, 1971). <<2 ~ (with Cinna Lomnitz, F. Hooser, C. P.. Allen, and W. Thatcher)

       "Seismicity and tectonics of the northern Gulf of California Region, Hexico. Preliminary Results.          Gee]'isica InternacionaZ,  ~  0:

37-48, Hexico, 1970. 3~ "Seismic Methods for Monitoring Underground Nuclear Explosions, an Assessment of the Status and Outlook", (Book Review) International Institute for Peace and Conflict Research (SIPRI) Stockholm, Sweden, BuZZ. Seism. Soc. Ames'. f~ (with W. Prothero, J. Dratler, B. Block) "Surface Wave Detection with a Broad-Band Accelerometer", l'/atua, 23Z:,21, 80-81 (Hay, 1971). (with J. Davies) "Regional and Global Fault Slip Rates from Seismicity", Ei1ature, 229, 101-107 (January, 1971).

       "Seismic Discrimination Between Earthquakes and Underground Exolosions",

statement and testimony at Hearings before Subcommittee on Arms Con rol, International Law and Organization, Ninety-second Congress of the U.S., First Session on Comprehensive Nuclear Test Ban Treaty, 139-149 (July 22-23, 1971). r p ~ (with Hax Wyss) "Regional Variations of Source Properties in Southern California Estimated from the Ratio of Short-to Long-Period Amplitudes", Bull. Seism. Soc. Amer., 6Z,1153-1167 (October, 1971).

       "A Deployment Program for Seismic Monitoring of a Comprehensive Test Ban Treaty", statement and testimony at Hearings before Subcommittee on Research, Development, and Radiation of the Joint Committee on Atomic Energy Congress of the U.S., Ninety-Second congress, First Session on Extent of Present Capabilities for Detecting and Determining Nature of Underground Events, 133-142 (October 27-28, 1971).
~

r~ ~ (with W. Prothero) "A Suitcase Seismic Recording System", BulZ. Seism. Scc. Amez'., 6Z, 6, 1849-1852 (December, 1971). (with D. McKenzie) "Melting on Fault Planes During Large Earthquakes", Gecpnus. J.B. as'. Soc, 29:1"(.1972). 4 ~ (with D. Oldenburg) "Ridge Transform Fault Spreading Pattern in Freezing Wax, Science, Vol. 178 (1972) 301. M-6

52. C. R. Allen, M. Myss, J. N. Brune, A. Grantz and R. E. Wallace.

          "Displaccments on the Imperial, Superstition Hills, and San Andreas Faults Triggered by the Borrego Mountain Eartnquake". In U.S.G.S., Prof. Paper 8787, pp. 87-104 (L972 ),

53. B. E. Tucker and J. N. Brune.. "Seismograms, S-Wave Spectra and Source Parameters for Aftershocks of the San Fernando Earthquake of February 9, t

1971." I/OAA Special Report, 1973,

54. I. Reid, M. Reichle, J. Brune and H. Bradner. "Microearthquake Studies using Sonobuoys: Preliminary Results from the Gulf of California."

Geophys. J'. B. astr. Soc., 34, 365-379 (1973). 55, J. N. Brune, S. de la Cruz, H. Bradner, C. Villegas, I. Reid, M. Reichle,

        'A. Nava, M. Lozada and P. Silva. "Earthquakes in the Gulf of California Recorded using Land-Based Recordings of Moored Hyd.ophone Arrays."

Geofisica Zrit., 12 (3), 201-212 (L972 ).

56. J. N. Brune and C. Lomnitz. "Recent Seismological Developments Relating to Earthquake Hazard." Geofisica Znt., 14: pp. 49-63 (1974),

"57. P. Molnar, B. E. Tucker and J. N. Brune. "Corner Frequencies of' 8 Models 'oE Earthqu'ake Sources,"'ull. Seismo. Soc. i'., and 63, 2091-2105 S Haves (1973).

58. F. Gilbert, A. Dziewonski and J. Brune. "An Informative Solution to a Seismological Inverse .roblem". Proc. Efat 'l. Acad. Sci., 70, 5, pp. 1410 ( 1973.).

59. W. Thatcher and J. N. Brune. " Surface waves and crustal structure 'n the Gulf of Californ'ia region." Bull. Seism. Soc. Am, 63, 5, 1689-3.698 (1973).

60. Brune, J. N. "Earthquake modelling by stick-slip along pre-cut surfaces in stressed foam rubber". Bull. Seism. Soc. Am., 63,.~. 6., 2105-2119.

( 197,3).

61. Brune, J. N. and F. Gilbert, "Torsional Overtone Dispersion from Correla-tions of S Waves to SS Waves", Bull. Seiam. Soc. Am., 64 (2), 313-320

          -(1974).

62. H. Bradner and J. Brune, "The Use of Sonobuoys in Determining Hypocenters of Aftershocks of the February 21,. 1973 Pt. Mugu Earthquake," ~l.l,.

Am., 64, No..l, 99-101, 1974.

63. J. N. Brune, "Current Status of. Understanding Quasi-Permanent Fields Associated with Earthquakes",'EOS, 55, No. 9, 1974.

t

64. D. M. Oldenburg and J. N. Brune, "An Explanation for the Orthogonality of Ocean Ridge" and .Transform Faults", J. Geophys. Res., 80, no. 17,

          .p. 2575, 1975.

65. Alfonso Reyes, J. Brune, L. Canalcs, J, Madrid, J, Rebollar, L. Munguia, T. Barker, "A Microearthquake Survey of the San Miguel Fault, Baja California, Mexico",Geophys, Res. Lttrs p 2) 56 59 3975.

M-7

1 James N. Bruno - B'ography Page

                                                                                        ~a 66,     James   Brune, Cinna Lomnitz, Clarence Allen, Fredorico Hooser, Francis I ohnor,
     ~

and Alfonso Reyes,"A Permanent Seismograph Array Around the Gulf of California," Z~li'. Soi.one. 8o'~. Am., 66, 969-978, 1976.

67. Ralph Archuleta and James N. Brune, "Surface Strong Motion Assoc-ated with a Stick-Slip Event in a Foam Rubber Model of Earthquakes " Bull, Soismo. Soc. Am., 65, 1459-1071, 1975.

68. Brian E; Tucker and J. N..Brune, "Source Hechanism and Surface-wave Excitation for Aftershocks of the San, Fernando Earthquake", Geophys.

J. R, astr, Soc,, 49 37>~426) >977r.

69. Hichaol Reichle, George Sharman, and James Brune,"Sonobuoy and Teleseismic Study of Two Gulf of California Transform Fault Earthquake Sequences",

Bull. Seisrrio. Soc. Amer., 66, 1623-1642, 1976.

70. 'illiam A'. Prothero., Ian Reid, Michael Reichle, James Brune, 'Ocean -Bottom Seismic Measurements on the East Pacific Rise and Rivera Fracture Zone",

Nature, 262, 121-124, 1976.

71. George F. Sharmanr Michael Sr Reichle> James. N, Brune, "A Detailed Study of Relative Plate Hotion in the Gulf of California," Geology, April; pp.

206-210$ 1976. II

72. Stephen H. Hartzell and James N. Brune, "Source Parameters for the January> 1975 Brawley Imperial Valley Earthquake Swarm" PAGEOPH, 115 1977.

73. James N. Brune, Alfonso Reyes, Michael S. Reichle, "Recent Seismic and

     'Tectonic Studies of the Gulf of California", CIBCASIO Annual Report, 1976.

74. James N. Brune, R. Archuleta, J. Frazier, G. Hegemier, "Physical and Numerical Modeling of Spontaneous Slip", sugary of talk given at Northwestern University at NSF Workshop on "Application of Elastic Waves in Electrical Devices, Non-Destructive Testing and Seismology" Hay 24-26, 1976.

1

75. James N. Brune,"Q of Shear Waves Estimated from S - SS Spectral Ratios," Geophys. Res. Lttrs., 4, No. 5, 1977.

.76. Stephen.H. Hartzell, Gerald A. Frazier and James N. Brune, Earthquake modeling in a homogeneous half=space,r'ull. Seism. Soc. A'm., 68, 301-316, '978.

77. Keith Priestley and James N. Brune, "Surface Waves and the Structure of the Great Basin of Nevada and Western Utah", accepted for publi-cation, 1977.

78. Luis Munguia, M, Reichle, A. Reyes, R. Simons, J. N. Brune, "Aftershocks of the 8 July 1975 Canal De Las Ballenas, Gulf of California, Earthquake",

Geaphysical'es. Lttr .', 4, No. 11, 1977. M-8:

79, J. N. Brune, "implications of Earthquake Triggering and Rupture Propa-gation for earthquake Prediction Based on Premonitory Phenomena", presented at USGS Conference on Fault Mechanics and its Relation to Earthquake Prediction, December 1-3, 1977.

80. J. N. Brune, R. J. Archuleta and S. H. Hartzell, "Far-Field S-Wave Spectra, Corner E'requencies and Pulse Shapes", presented at on Fault Mechanics and its Relation to Earthquake Prediction USGS'onference December 1-3, 1977..

81. Stephen Hartzell, James N. Brune and Jorge Prince, "The Acapulco E'arthquake and the importance of Short Period October 6, 1974 Strong Ground i~fotion, in preparation, 1978. Surface Waves in

82. James N. Brune, "Statement to the ACRS" meeting meet o f t h e Subcommittee S b of the Advisory Committee on Reactor Safeguards, Los Angeless, Califo a ornia,

83. Stephen Hartzell and James N. Brune, "Analysis of the Bucharest Strong Ground Motion Record for the March 4, 1977 Romanian Earthquake", in preparation, 1978.

84. A. Reyes, J. N. Brune and C. Lomnitz, "Source Mechanism and Aftershock Study of the Colima, Mexico Earthquake of January 10, 1973", in pre-paration, 1978.

85. Stephen Hartzell and James N. Brune; "The Horse Canyon Earthcuake of August 2, 1975 Two Stage Stress Release Process in a Strike-Slip Earthquake", in preparation, 1978.

M-9

~ k ~

 ~

~ ATTA IEI<T N Curxiculum Vitae for J. Enrique Luco Birth Date: May 18, 1943 - Vina del Mar, Chile Education: Ph. D. University of California, Los Angeles - 1969. Civil Engineer, University of Chile, Santiago - 1967. W Scientific Research: Includes studies on the effects of geology and local site conditions on earthquake ground motion; dynamxc response o~ zoundaticns; "oil-str"ct rc

                                                                           ~

interaction during earthquakes; wave propagation on a simplified model of the Earth; evaluation of earthquake damage; earthquake response of nuclear power plants; forced vibxations of structures. Employment; Associate Professor of Applied Mechanics, University of California, San Diego, 1977<<present. Assistant Professor of Applied Mechanics, University of California, San Diego, 1974-1977. Senior Research Fellow in Applied Science, California Institute of Technology,'973-1974. Researcher, Department of Geophysics, University of Chile, 1970-1973. Professor in the Departments of Mathematics and Physics, University of Chile, 1971-1972. Research Fellow in Applied Sciences, California Institute of Technology, 1970. Research Assistant, Department of Geophysics, Unive r sity of Chile, 1965- 1967. Professional Societies Membership: American Society of Civil Engineers. Seismo)ogical Society of America. Am'erican Academy of Mechanics. Sigma Xl,

Publications of J. E. 'Luco

l. 1967. Pro a ation of Hi h-Fre uenc Com ressional Pulses in a La ered Sphere, Civil L'ngincer Thesis, Facetted de Ciencias Fisicas y Matematicas, Universidad de Chile, Santiago, Chile (Publication No. 45, Department of Geophysics, University of Chile, Santiago).

2. 1969. "Dynamic Interaction of a Shear Wall with the Soil," J. Engineering Mechs. Div., ASCE, Vol. 95, No. EM2, April, pp. 333-346..

3. 1969. A lication of Singular Inte ral E uations to the Problem of Forced Vibrations of a Ri id Foundation, Ph. D. Dissertation, School of Engineering and Applied Science, University of California, Los Angeles.

(December). ~

4. 1970. "Dynamic Soil-Structure Interaction," with Hradilek, P. J., Informe Tecnico No. 14 Instituto de Investigaciones Ensa es de Materiales (IDIEM), Universidad de Chile, Santiago, Chile.

5. 1970. "Strong Earthquake Motion and Site Conditions: Hollywood, " with Duke, C. M., Carriveau, A. R., Hradilek, P. J., Lastrico, R.,

and Pstrom, D., Bull. Seisme Soc. Amer., Vol. 60, No. 4, August, pp'. 1271-1289.

6. 1971. "Dynamic Response of Circular Footings," with Westmann, R. A.,

Engineering Report No. 7113, School of Engineering and Applied Science, University of California, Los Angeles (April). 7.'971. "Dynamic Response of Circular Footings," with Westmann, R. A., J. En ineerin Mechs. Div., ASCE, Vol. 97, No. EM5, October, pp. 1381-1395.

8. 1971. "Informe Preliminar, sobre Intensidades y Danos causados por el Sismo de 8 de Julio de 1971: Zona Calera - Illapel," with Lastrico, R., and Medone, C. A., Revista Geografica, de Chile, No. 21, pp.

14-19, Santiago, Chile.

9. 1972. "A Preliminary Report, The July 8, 1971 Chilean Earthquake, " with Eisenberg, A., and Husid, R., Bull. Seisme Soc. Amer., Vol. 62, No. 1, February, pp. 423-430.

10, 1972. Dynamic Response of a Rigid Footing Bonded to an Elastic Half-Space," with Westmann, R. A., J. A l. Mech., ASME, Vol. 39, Series E, No. 2, June, pp. 527-534. N-2

~ ~ a ~ ll, .1972. "El Terremoto de San Fernando en California," with Lastrico, R., Revista de la Construccion, Ano XI, No. 117, Junio-Julio, Santiago, Chile. r r "Ingenieria Sismica en Chile: una Bibliografia, " Informe Tecnico r r ~ ~

12. 1972.

No. 15, Instituto de Investigaciones Ensa es de Materiales (IDIEM), Universidad de Chile, Santiago, Chile.

13. 1973. "Dynamic Structure-Soil-Structure Interaction," with Contesse, L.,

Bull. Seism. Soc. Amer., Vol. 63, No. 4, August, pp. 1289-1303.

14. 1973. "Vibraciones Horizontales de un Disco Rigido sobre un Semiespacio Elastico," Revista del Instituto de Investizaciones Ensaves de Materiales (IDIEM), Vol. 12, No. 1, pp. 1-13, Universidad de Chile, Santiago, Chile.

15. 1974. "Soil-Structure Interaction - Continuum or Finite Element", "with Tsai, N. C. and Hadjian, A. H., Nuclear En~ineerin and Design, Vol. 31, No. 2, pp. 151-167.

16, 1974. "The Dynamic Modeling of the Half Plane by Finite Elements," with Bos, H., and Hadjian, A. H., Nuclear En ineering and Design, Vol. 31, No. 2, pp. 184-194.

17. 1974. "Two-Dimensional Approximations to the Three-Dimensional Soil-Structure Interaction Problem," with Hadjian, A. H., Nuclear En ineerin and Desi, Vol. 31, No. 2, pp. 195-203,

18. 1974. "Impedance Functions for a Rigid Foundation on a Layered Medium,"

Nuclear En ineerine and Design, Vol. 31, No. 2, pp. 204-217,

19. 1975. "Full Scale, Three DiiYlensio.al Tes o Str ct r 1 De ormations During Forced Excitation of a Nine-Story Reinforced Concrete Building," with Foutch, D. A., Tzifunac, M. D., and Udwadia, F. E., Procecdin s U.S. Nation" 1 Conference on Earthquake 9

20. 1975. "An Experimental Study of Ground Deformations Caused by Soil Structure Interaction," with Trifunac, M. D., and Udwadia, F. E.,

Proceedings U.S. National Conference on Earth uake En~ineerin June, 1975, Ann Arbor.

21. 1975. "A Note on the Dynamic Response of Rigid Embedded Foundations,"

with %'ong, H. L., and Trifunac, M. D., Earthquake Engineering and Structural Dynamics, Vol. 4, No. 2, pp, 119-128.

22. 1975. "Dynamic Modeling of a Viscoelastic Half-Space by Finite Elements,"

with Hadjian, A. H. and Atalik, S., Proceedings Second ASCE Conference on Structural Desi n of Nuclear Plant Facilities, December, 1975, New Orleans.

23. 1976. "Torsional Response of Structures to Obliquely Incident SH Waves," Earth uake En ineering and Structural namics, Vol. 4, No. 3, January-March, pp. 207-219.

24. 1976. "Torsional Response of Structures for SH-Waves: the Case of Hemispherical Foundations," Bull. Seism. Soc. Amer., Vol.

66, No. 1, February,,pp. 190-123.

25. 1976. ",Vibrations of a Rigid'Disc on a Layered Viscoelastic Medium,"

Nuclear En ineering and Desi n, Vol. 36, No. 3, March, pp. 325-340.

26. 1976. "Torsion of a Rigid Cylinder Embedded in an Elastic Half-Space," Journal of Ap lied Mechanics, Vol. 43, Series E, No. 3, September, pp. 419-423.

27. 1976. "Dynamic Response of Rigid Foundations of Arbitrary Shape,"

6, *- *.. with Wong, H. L., Earth I ake Engineering and Structural 9-9 28, 1976. "Torsional Response of a Rigid Embedded Foundation," with Apsel, R. J., J. of the En@re. Mech. Dives ASCE, Vol. 102, No. EM6, December, pp. 957-970.

29. 1977. "Dynamic Response of Rectangular Foundations for Rayleigh Wave Excitation," with Wong, H. L., Proceedings of the Sixth World Conference on Earth uake Engineering, New Delhi, India.

30, 1977. "On the Importance of Layering on the Impedance Functions," with Hadjian, A. 'H., Proceedings of the Sixth World Conference on Earth uake Engineerin, New Delhi, India.

31. 1977. "Contact Stresses and Ground Motion Generated by Soil-Structure Interaction," with Wong, H. L. and M. D. Trifunac, Earthqualce En ineerinz and Structural namics, Vol. 5, No. 1, January-March, pp. 67-69.

32. 1977. "The Application of Standard Finite Element Programs in the

           'Analysis of Soil-Structure Interaction, with Wong, H. L., Proc.

99 of the Second SAP User's Conference, Umversit of Southern California, June 1977, Los Angeles.

       ~   ~

l~ E I ~ I

33. 1977. "Seismic Response of a Periodic Array of Structures," with Murakami, H., Z. of the Engrg, Mechs. Div., ASCE, Vol. ~103 No. EM5, Oct. pp. 96~-977.

r

34. 1978. "Dynamic Response of Rectangular Foundations to Obliquely "it En ineerin and Structural D amies, Vol. 6, Zan., pp. 3-16.

N-5

P

"~
     ~

hi,

~'

  ~
    ~ ~

ATT NEHT 0 CURRICULUM.VITAE FOR iVIIHAILO D. TRIFUNAC ggG ] 7 578 Birth Date: 7 November 1942 K'kinda, Yugoslavia Ed" ca on: Pn. D. Califor .i Inst'tute of Te" hnology, Civil Enginee" ing and Geophysics, 1969 M. S. Princeton. University, Civil Engineering, 1966 B. S. University of Belgr-de, Civil Engineering, 1965 Scientific Research: Includes investiga ion of strong earthquake ground. motions following Parkfield, California, 1966 earthquake (1967+); high-frequency resolution and strong-motion mechanism study of Imperial Valley, California 19-"0 earthquake (1968+); siznple mathematical models of an alluvial valley subject to strong earthquake motion (1968+); ambient and forced vibration studies of several multi-story structures (1968+); laboratory evaluation instrument correction methods of strong motion accelerogzaphs 'nd, ()970+); development of the data processing methods of strong-motion accelerograms (1970+); s atistics and triggering mech" nism of earthquakes (1968+); studies of microtremor vibrations the Imperial Valley (1970+); study of net methods for synthesizing artificial strong ground zwotion (1970+); invest gation of the soil-structure interaction (1970+); amplification and. focusing effects in complicated geologic structures (1971+); stress estimates and . source mechanism studies of earthquakes based, on the recorded strong -motion ace elex ograms (1971); development of seismic design criteria. in terms of respozise spectra (1975+); developr .ent of approximate scaling methods foz strong earthquake ground mot on in terms of peak accelerations, velocities and displa'ements (1975+); studies on duration of strong ea thquake ground mot'on (1974+); soil-bridge-soil interaction'roblems (1975+); soil-structure-soil.-structure interaction problezns (1975+).

        ~l               pro>c:nOv C~g gg,L gbpillCC Ip ) Qp$ J0p+p g g~
                                                   ~ ~

Qp(.JJQ)Q ~/Oft(l ' '( I (0 ssistant Professor of Applied S'cience, Calif'ornia Institute of

                                                                          ~

Technology, 1972- l'l')~ Research Associate, Lamo..t-Doherty Geological Observatory and Lecturer in the Department of Geology of Columbia University, 1971-1972 Research Scientist, Lamont-Doherty Geological Observatory of Columbia Univer si ty, 1970- 1971 Research Fel'o.v '..n Applied lvlechanics, California Institute of Technology, July 1969-September 1970 0-1

M. D. Trifunac Curriculum Vitae t i ~ ~ Page Tv'o Research Assistant, California Institute of Technology, 1966-1969 Research Assistant, Princeton University, 1965-1966 Consultant to Advisory Committee on Reactor Safeguards, 1971-Prof ssional Societies: American Geophysical Union American Society of Civil Engineers Seismological Society of America Sigma Xi Earthquake Engineering Research Institute Teaching~ Experience: Columbia Univer sity: l. .3'Ij 6940y '- Strong-Motion Seismology (1971-72) Caltech: -2. CE180 Experimental Methods in Earthquake Engineering CE181 - Principles of Earthquake engineering 4, CE1 S2 - Str uc tura1. Dynamic s of Earthquake Engineering Other Selected Activities and Ewmerience: on the Panel on Strong-Motion Seismology, Committee

    'nServed Seismology,'at. Acad. of Sciences; Participated. in UNESCO
                                             -Motion               Participated, Symposium of Experts     on    Strong            Seismology; in ATC-3 effort for improvement of Earthquake Resistant Design Code; Presented over 50 scientific papers during national and international conferences.

0-2

 ~,     g     ~

~ ~

          ~
      ~

Scientific Publications of.M. D. Txifunac

1. 1967 Analysis of accelerograms - Parkfield earthquake, with G. W.

Housner, Bull. Seism. Soc. Amer., 57, 1193-1220.

                                                                    'I Z. 1969 Analysis of strong-motion accelerograph records, with D. E.

Hudson and N. C. iXigazn, Fourth World Conference on Ea r thqua ke Engineering, Santiago, Chile.

3. 1969 Strong-motion earthquake accelerograms, digitized and plotted.

data, Vol. I, with D. E. Hudson and A. G. Brady, Earthquake Engineering Research Laboratory, EERL 70-20, California Institute of Te chnology, Pasadena.

4. 1969 Investigation of stxong eaxthquake ground 'motion, Earthquake Eng. Re s. Lab., Calif. Inst. of Tech., Pasadena.

5. 1970 Analysis of the station No. 2 seismoscope record - 1966, Parkfield, California, earthquake, with D. E. Hudson, Bull.

Seism. Soc. Amer., 60, 735-794.

6. 1970 Wind and microtremor induced vibrations of a 22-story steel frame building, Earthquake Eng. Res. Lab., EERL 70-.01, Calif. Ins t. of Tech., Pasadena.

7. 1970 Complexity of energy release. during the Imperial Valley, California,, earthquake of 1940, with Z. N. Brune, Bull. Seism.

Soc. Ame r., 6 0, 137-16 0.

8. 1970 Ambient vibration test or a 39-story steel frame building, Earthquake Eng. Res. Lab., EERL 70-02, Calif. Inst. of Tech.,

Pasadena.

9. 1970 On the statistics and possible triggering mechanism of earth-EERL 70-03, Calif. Inst. 'f quakes in Southern California, Earthquake Eng. Res. Lab.,

Tech., Pasadena.

10. 1970 Laboratory evaluation and instrument coxrections of strong-motion accelerographs, Earthquake Eng. Res. Lab., EERL 70-04, Calif. Inst. of Tech., Pasadena.

11. 1970 Response envelope spectrum and interpretation of strong earth-quake ground motion, Earthquake Eng. Res. Lab., EERL 70-06, Calif. Inst. of Tech., Pasadena..

12. 1970 Low frequency digitization errors and a new method for zero baseline correction of strong-motion accelerograms, Earthquake Eng. Re s. Lab., EERL 70-07, Calif. Inst. of Tech., Pasadena.

0-3

I 1971 Response envelope spectrum and interpretation of strong earth-quake ground motion, Bull. Seism. Soc. Amer., ~61 343-356.

14. 1971 Zero baseline correction of strong-motion accelerograms, Bull.

Seism. Soc. Amer., 61, 1201-1211.

15. 1971 A method for synthesizing realistic strong ground motion, BulL.

Seism. Soc. Amer., ~61 1755-1770.

16. 1971 Surface motion of a semi-cylindrical alluvial valley for incident plane SH waves, Bull. Seism. Soc. Amer., 61, 1739-1753.

17. 1971 Analysis of the Pacoima Dam accelerogram, Sm Fernando, California, earthquake of 1971, with D. E. Hudson, Bull. Seism.

Soc. Amer., ~61 1393-1411.

18. 1971 High frequency errors and instrument corrections of strong-motion accelerograms, with F. E. Udwadia and A. G. Brady, Earthquake Zng. Res. Lab., EERL 71-05, Calif. Inst. of Tech.,

Pasadena. 19 1971 Strong-motion earthquake accelerograms, II, corrected accelero-grams and integrated velocity, and displacernent curves, with D. E. Hudson,. A. G. Brady and A.'ijayaraghavan, Earthquake Zng. Res. Lab., EERL 71-51, Calif. Inst. of Tech., Pa,sadena.

                                                                    =

20. 1971 Engineering features of the San Fernando earthquake, February 9, 1971, Chapter II, edited by P. C. Jennings,. Earthquake Eng.

Res. Lab., "ZERL 71-02, Calif. Inst. of Tech., Pasadena.

21. 1972= Strong-motion accelerograms, III, response spectra, with D. E.

Hudson and A. G. Brady, Earthqua.ke Eng. Res; Lab., EERL 72-80, Calif. Inst. of Tech.

22. 1972 Strong-motion earthquake accelerograms, IV, Fourier spectra, with D. E. Hudson, F. E. Udwadia, A. Vijayaraghavan, and A. Brady, Earthquake Eng. Res. Lab., ZERL 72-100, CalU.

Inst. of Tech., Pasadena.

23. 1972 Interaction of a shear wall with the soil for incident plane SH

          . waves, Bull. Seism. Soc. Amer., 62, 63-83.

24. 1972 A note on correction of strong-motion accelerograms for instrument response, Bull. Seism. Soc. Amer., ~62 401-409.

25. 1972 Stress estimates for San Fernando, California," earthquake. of 9 February 1971: itin event and thirteen aftershocks, Bull.

Seism. Soc." Amer., 62, 721-750.

26. 1972 Tectonic stress and source mechanism of the Imperial Valley, California, ea,rthquake of 1940, Bull. Seism. Soc. Amer., ~62 1283- 13 02.

0-4

~ / between ambient and forced vibration experiments, 0'ompaxison Int. J. of Earthquake Eng. and Struct. Dynamics, ~l 133-150.

   $ ",ud:es of strong earthquake motions and microtremor processes, with F. E. Udhvadia, 'International Conf. of i>iicrozonation, Seattle, Wa shington.

Analysis of errors in digitized strong-motion accelexograms, with F. E. Udwadia, and A. G. Brady, Bull. Seism. Soc. Ame'r., o3, 157-187. A note on scattering of plane SIC waves by a semi-cylindrical canyon, Int. J. of Earthquake Eng. and, Struct. Dynamics, ~1 267-281. Characterization of response spectra by parameters governing the'ross nature of earthquake source mechanism, 53VCEE, Rome, Italy. Recent developments in data processing and accuracy evaluations of strong-motion acceleration measurements, with F. E. Udwadia and A. G. Brady, 5V;CEE, Rome, Italy.-- Ambient vibration tests of full-scale structures, with F. E. Udwadia, 577CEE, Rome, Italy. Comparison of earthquake and microtremor ground motions in El Centro, California, with F. E. Udwadia, Bull. Seism. Soc. Amer. ~63 iso. 4, 1227-1253. Analysis of stron~ earthquake ground motion for prediction -of response spectra, Int. J. of Earthquake Eng. and Struct. Dynamics, Vol. 2, No. 1, 59-69. The Fourier transform, response spectxa and their relationship through the statistics of oscillator response, with F. E. Udwadia, Earthquake Eng. Res. Lab., EERL 73-01, Calif. Inst. of Tech. Damped Fourier spectrum and response spectra, with F. E. Udwadia, Bull. Seism. Soc. Amer., 63, 1775-1783. Routine computer processing of strong-motion accelerograms, with V. Lee, Earthquake Eng. Rcs. Lab., EERL 73-03, Calif. Inst. of Tech. Characterization of response spectra through the statistics .of oscillator response, with 1". E. Udwadia, Bull. Seism. Soc. Amer., ~64 205-219. A three-dimensional d'slocation model for the San Fernando, California, earthquake of February 9, 1971, Bull. Seism. Soc. Ame r., 64, 149-172. 0-5

41.. 1974 Parkfield, California, earthquake of June Z7,'966: a three-dimensional moving dislocation, with F. E. Udwadia, Bull. Seism. Soc. Amer., 64, 511-533. 4Z. 1974 Time and amplitude dependent response of structures, with F. E. Udwadia, Intl. J. of Earthq. Engr.. and Struct. Dyn.

          ~2 359-378.

43. 97 A A note on the accuracy of computed ground displaceznents frozn strong motion accelerograms; with V.. W. Lee, Bull. Seism. Soc. Ame r., 64, 12 09-1Z19.

44. 1974 Variations of strong earthquake ground shaking in the Los Angeles area, with F. E. Udwadia, Bull. Seiszn. Soc. Amer.,

64 1429-1454.

45. 1974 Scattering of plane SH-waves by a sezni-elliptical canyon, with H. L. Wong, Intl. J. of Earthquake Engr. and Struct.

Dyn., ~3 157-169. 46.. 1974 Surface motion of a semi-elliptical aQuvial valley for incident plane SH-waves, with H. L. Wong, Bull. Seism. Soc. Azner., 64, 1389-1408.

47. 1974 Interaction of a shear wall with the soil for incident plane SH waves: elliptical rigid- foundation, w th H. L. Wong, Bull. Seism. Soc. Amer., ~64 1825-1842.

48. 1975 An array of .strong znotion accelerographs in Bear Valley, California, with R. J. Dielznan and T. C. Hanks, Bull.

Seism. Soc. Amer., ~65 l-lZ.

49. 1975 A note on the dynamic response of rigid, embedded foundations, with J. E. Luco and'. L. Wong, submitted to Intl. J. of Earthquake Eng. and Struct. Dyn.

50. 1975 On the correlation of seismic intensity scales with the peaks of recorded, strong ground. motion, with A. G. Brady, Bull. Seism. Soc. Amer., 65, 139-162.

51. 1975 On the correlation of seismoscope response with earthquake magnitude and Modified iviercalli intensity, .with A. G. Brady, Bull. Seism. Soc. Azner., 65, 307-321.

52. 1975 A study on the duration of strong earthquake ground motion, with A. G. Brady, Bull. Seism. Soc. Amer., 65, 581-626.

53. 1975 Two-dimensional, antiplane, building -soil-building interaction for two or more buildings and for incident plane SH-waves with H. L..Wong, submitted to Bull. Seism. Soc. Amer.

0-6

Correlations of peak acceleration, velocity and displacement with earthquake magnitude, distance, and site conditions, with A. G. Brady, Intl. Z. of Earthquake Engr. and Struct.. Dyn. (in press). On the correlation of peak accelerations of strong motion with earthquake magnitude, epicentral distance and site conditions, with A. G. Brady, Proc. U. S. National Conference on Earthquake Engineering, Ann Arbor, Michigan, 43-52. Preliminary analysis of the peaks of strong earthquake ground motion - dependence of peaks on earthquake magnitude, epicentral distance and the recording site conditions, Bull. Seism. Soc. Amer. (in press). t.ull scale" three-dimensional tests of structural deformations during forced excitation of a nine-story reinforced concrete build ng, with D. A. Foutch, Z. E. Luco, and F. E. Udwadia, Proc. U.S. National Co'nference on Earthquake Engineering, Ann Arbor, Michigan 206-215. An experimental study of ground deformations caused, by soil-structure interaction, with Z. E. Luco and F. E. Udwadia, Proc. U. S. National Conference on Earthquake Engineering, Ann Arbor, Michigan, 136-145. Influence of a canyon on soil-structure interaction, with H. L. AVong, J. Engr. Mech. Div., ASCE (in press). Antiplane dynamic soil-bridge-soil interaction for incident plane SH-waves, with A. M. Abdel-Ghaffar, Intl. Z. of Earthquake Eng. and Structural Dyn. (in press). p A note on the rang e of peak amplitude s of record ed accelerations, velocities and displacements with respect to the Modified Mercalli intensity, Earthquake Notes (in press). Contact stresses and ground motion generated by soil-structure interaction, with H. L. Wong and J. E. Luco, submitted to Intl. Z. of Earthquake Eng. and Struct. Dyn. Preliminary emoirical model for scaling courier amplitude spectra of strong ground acceleration in terms of earthquake magnitude, source to station distance and recording site conditions, Bull., Seism. Soc. Amer. (in press).. Dependence of duration of strong earthquake ground motion on magnitude, epicentral distance, geologic conditions at the recording station and frequency of motion, with B. Westermo, submitted to Bull. Seism. Soc. Amer. 0-7

                                                                          ~  i ~ ~

65. 1976 On the comparison of experimental and theoretical analyses of the effects of surface and subsurface irregularities on the amplitudes of monochromatic waves, with H. L. Wong and B. Westermo, submitted to Bull. Seism. Soc. Amer.

66. 1976 Correlations of frequency dependent duration of strong earthquake ground motion with the Modified Mercalli.

Intensity and the geologic conditions at the recording stations, with B. Westermo, submitted to Bull. Seism. Soc. Amer.

67. 1977 'n instrumental and comparison Medvedev-Karnik-Sponheuer of the Modified Mercalli (M. M. l. )

(M. K. S. ) Intensity scales, Sixth World Conf. Earthquake Engineering, New Delhi, India.

68. 1976 Effects of cross-axis sensitivity and misalignment on the xesponse of mechanical-optical accelerographs, with H. L. AVong, submitted to Bull. Seism. Soc. Amer.

69. 1977 Antiplane dynamic soil-bridge-soil interaction for incident plane SH waves, with Abdel-Ghaffar, Sixth world Conference Earthquake Engineering, New Delhi, India.

70. 1977 Statistical analysis of the computed response of structural

         'response recorders (S. R. R. ) for accelerograms recorded in the United States of America, Sixth world Conference Earthquake Engineering, New Delhi, India.

0-8

I s ] i / f J

        ~
          ~

I' ~ I

                     ~

s

                                                                              ~ ATTACHMENT P
                           ~ orro ~, ~ o    ~ ~  * ~   ~                              ~  ~
   'I          fl
                         ~      ~       ~

l REYIG'f OF TllE 'SEIShlIC EYALUATION FOR

                                                           ~

POSTULATED 7.5hf IlOSGRI EARTNQUA}:E, UNITS l AND 2, DIABLO CANYON SITE'y J. Enzique Luco A Rcport to the Advisory Committee on Reactor Safeguards U. S. Nuclear Regulatory I Commission.

                                        ~ 1 50 hhy 1978

REYIEIf AND RECONlENDhTIONS After dctailcd review of thc rcport 'Seismic Evaluation for postulated 7. 5~if llosgri Earthquake'Rcf. 1),. I have thc following comments and rccommcndations:

l. Frcc-Field Desi .n Sncctrum. In my opinion, the frcc-field design spectrum used for rc-evaluation of thc Diablo Canyon Nuclear Power Plant docs not reflect the strong motion at thc site for a 7.5 magnitude earthquake at an epicentral distance of 5 kilometers, but rather the motion for a 6.Sic earthquake at that distance. The free-field design spectrum developed by Newmark and adopted by NRC corresponds to a simplified version oi the average of the two Pacoima Dam spectra recorded during the 6.5A'an Fernando earthquake with the high-frequency portion reduced by use of'n 'effective'eak acceleration (Fig. 1). Thc Blunts design spectrum developed for the applicant closely follows the Newmark spectrum. The peal; acceleration, velocity and displace-I controlling the high, intc'rmcdiate and low ircqucncy portions

                                              'ent of thc Ncwmark design spectrum arc in agrccmcnt with the average (50'ercentile) peak valdcs obtained by Trifunac (Ref. 2) for a h

6.5ht earthquake while falling short by 40 to 60 percent from the corresponding values for a 7.5hf earthquake (Table 1). The peak values consistent with thc Ncwmark spectrum arc also considerably lower than those 'suggcstcd in USGS circular 672 (Rcf.. 3) as shown in Table'1. In addition, comparison of thc Ncwmark and Blumc dc-sign spectra with cstimatcs of thc avcragc rcsponsc spectrum for qo

                 ~   ~ ~ I     ~
                 ~     P-2 I

~ n ' ~ a 7.5)4 carthquakc as obtained by Trifunac (Rcf. 4) also shows diffcrcnccs of thc order oi 30 to 50 pcrccnt (Fig. 2). The applicant has indicated that thc thrust fault mech"nism and thc location of the Pacoima Dam instrument in thc San Fernando earthquake may have incrcascd thc recorded peak acccl-eration. These possible cficcts arc ncgligiblc in view of thc fact that the standard deviation for peak accclcrations, which has,not been considered, corresponds to a factor of 2. Also, thc records ior thc hfs=7.2 Gazli, Russia earthquake of 1976 indicate a peak horizontal acceleration of 0.8g at an epicentral distance of 10 kilometers. Correcting for attenuation using the Gutenberg's relation leads to a peak acceleration of 1.0g at 5 kilometers for thc Gazli earthquake in general agrcemcnt with the results of Trifunac and thc USGS rccommcndation (Table 1). Xn view of these facts, I must, conclude that thc Ncwmark and Blumc design spectra do not corrcspond to the ground motion for a 7.5'arthquake at an epicentral distance of 5 kilometers. I pro-pose that the estimate of the average response spectrum for 51=7.5, 5 kilometers, epicentral distance and rock sites of Trifunac (Rcf.

4) bc used as design spectrum. This spectrum is consistent with thc only records availablc for large magnitude and short epiccn-tral distances (San Fernando, Koyna and Gazli) as well as with thc USGS circular 672 rccommcndations.

2~ 'Efi'cctivc'eak Acceleration. A judgmental iactor has bccn used to rcducc thc 1.15g peak accclcration rccommcndccl in USGS circular 67 to a value oC. 0.75g. This ill-dcCincd Cactor C P-3

e t has bccn used in thc past to account for discrcpancics on thc level of damage obscrvcd as compared with thc prcdiction o f ordinary seismic analyses which do not account for thc effects of soil-structure interaction, are based on nominal values for damp-ing and strength, assume linear behaviour a>>d do not include the energy dissipation in partitions and other non-structural clc-ments. This catch-all reduction factor. has no place in the de-sign of carefully analyzed structures such as those xn nuclear power plants. Factors which may reduce the response or thc level of damage should be identified and properly included in thc struc-tural models. In the case of Diablo Canyon, many of these factor . have already been incorporated in thc analysis: use of tc-t strength rather than nominal values, use of higher than common

   ~

damping values, reduction by scattering of waves by large founda-tions and possible inclusion of ductility. Thc arbitrary reductio.-. of the high-frequency components of motion affects the response piping and equipment. I recommend the. elimination of this reduc-tion of the input motion.

3. On thc Effect of Scattering of Navcs b Ric.id Foundations.

Thc high-frcquc>>cy components of the free-field motion have been reduced by thc so-called tau-filtering procedure to account by the scattering of waves by thc supposedly rigid foundations. This correction amounts to a reduction of the Ncwmark free-field design spectrum by 20 to 30 pcrccnt for frcqucncics higher than 2cps. Slightly lower reductions have bccn used in thc Blumc's spectrum. Thc correction for foundation scattering effects is based on thc

                                       ~ ~
                                ~  ~ g P-4

assumption of a rigid foundation and horizontally propagating Sll waves. Although thc a" sumption of a rigid foundation may bc rca-sonablc, it must be rccognizcd that deviations from thc assumption lead to localized higher stresses in thc lower portions of thc diffcrcnt structures. The assumption of horizontally incident Sfl waves is highly questionable considering that thc epicentral dis-tancc is comparable with the focal depth. Under thcsc conditions, the possibility of nearly vertically incident.waves may not bc ruled out. For vertically incident waves the scattering by the foundations is practically nonexistent given thc shallow embed-ment. Assuming for the sake of the argument that the seismic exci-tation at thc site corresponds x~ horizontally incident Sll waves, I find that thc reductions proposed by Ncwnark and Blumc arc too high when compared with analytical solutions. For hori"ontally incident Sll waves the reduction of thc translational components of motion is coupled with thc pxistencc of a marked torsional input to the structure (for details refer to the attached papers). The applicant has included 'accidental'ccentricities of 5 and 7 percent to represent these torsional effects. The usc of an eccentricity of 5 percent corresponds to thc use of a peak tor-sional acceleration at thc base of thc containmcnt of thc order of 0.025 rad/scc2 as may bc infcrrcd from Table 4-5 of Pcf. '1. This torsional accclcration corresponds to a tangential accclcr" ation at thc base of thc containmcnt cxtcrior.of 0.025 x 70/52= 0.05g. Thc results of Ray and Jhavcri of URS/131umc prcscntcd in

                                                            ~  P  ~

Fig. 56 of Appendix D39A, but not used in thc analysis, show that a peak torsional acceleration of thc order of 0.1 rad/scc 2 corrcs-ponding to a peak tangential accclcration at thc base of thc con-tainmcnt exterior of 0.2g 'would be morc appropriate. It may bc concluded that thc use of a 5 percent eccentricity undcrcstimatcs thc torsional input by a factor of four. This ob" crvation is con-sistent with the original work of Ncwmark (Ref. 5) which indicates that an eccentricity of the order of 25 percent would bc necessary to represent the torsional effects induced by horizontally propa-gating Sll waves. It must be mentioned that thc increase in peak acceleration of 0.2g based on a more realistic estimate of the torsional input more than compcnsatcs for thc reduction by tau-filtering from 0.75g to O.G7g for the containment exterior. From the point of view of thc analysis of the structural re-sponsc, it docs not seem adequate to introduce the torsional inpu-thxough the usc of 'accidental'ccentricities. Such procedure which )cads to thc coupling of thc torsional and translational rc-sponsc in essentially symmetric structures distorts thc rcsponsc and thc natural frcqucncios of thc system. Thc effects of thc tcr-sional input may bc significant fo- the turbine building in .which thc possibilit'y of portions of the structure undergoing inelastic dcformations may increase thc eccentricity. If it is shown that thc seismic excitation at thc site cor-I'csponds mainly to horizontally incident waves, thc reductions of thc translational and torsional response should bc cvaluatcd on thc basis of thc morc exact methods presently availablc. To

                                 ~  ~

include an cxaggcratcd reduction of thc translational motion with-out incorporating thc full torsional cffccts is improper. Soil-Structure Interaction. In Appendix D-LL3A of Rcf. 1, thc applicant presents a comparison of thc results obtained by the fixed base analysis of the axisymmetric containmcnt nodcl with tau-filtcred spectra as input (F.B.Axisym.) with those obtained fron a soil-structure interaction finite clcmcnt model with the NcwmarL; free-field motion (without tau-filtering) used as surface'control motion (PLUSl<-SSI). Based on the results shown in Fig. 3A-1 of Appendix D-LL3A, the applicant concluded that 'thc use of tau-filtered inputs with fixed base models as used for seismic analys"s of Diablo Canyon structures is conservative.'his comparison is not valid, and the c'onclusion is not warranted by thc analysis. Ior a valid comparison, we must require that the fixed base axis-ymmctric analysis and the fixed base PLUSll analysis give esscnti thc same response cvcrywhcre except at high frequencies whcrc thc fixed base PLUSll results not.irfcluding thc tau-filtering should be slightly higher. This is not thc case as shown in Fig. 3 of this rcport obtained from results shown in Figs. 3A-1 and 38-5 of Appendices D-LL3A and D-LL33. Since thc fixed base PLUSll mod 1 is inconsistent with thc fixed base axisymnctric model, no valid

  ~

conclusion as to thc effects of soil-structure interaction can be obtained by comparisons of thc type shown in Fig .. 3A- l. It mus t bc mentioned that it has bccn shown that two-dimensional models such as PLUSll may undcrcstimatc thc rcsponsc at thc top of thc structure by 30 to 50 pcrccnt. P-7

4'

                                                         ~

In Appendix D-LL3B, comparisons arc prescntcd oi thc rcsponsc for a fixed base and an SSI model both computed using PLUS)l and V thc Ncwmark free-field spectrum (without tau- fi3.tcring) as control motion on thc frcc-surface. Assuminp that thc results prcscntcd arc internally consistent, it is possible to draw some tentative conclusions. Fig. 38-2 of Appendix D-LL38 indicates that'he pca); accclcrations'n the containmcnt cxtcrior obt'aincd including thc SSI effects are approximately 10 pcrccnt lower than those obtained on a rigid base. Since thc SSI result" automatically include the cffccts of scattering of waves by the foundation as well as the ci'fccts of radiation damping into thc soil, it'ay be concluded that the reduction of 20 percent (0.75g to 0.6g) by tau-eff ct proposed by Newmar)'nd a similar reduction used by Blumc arc not conservative. Figs. 3B-3 and 38-4 of the same Appendix indicate that thc story shear forces and overturning moments on the contain-ment exterior obtained including thc SSI are equal or slightly higher than those obtained for t)ie rigid base PLUS)) model. In this case, any reduction of thc fixed base results by tau-filtering would underestimate thc stresses in thc structure. Assuming that .he PLUS)i results are correct and consistent, it may be concluded that thc tau reduction proposed by Hcwmar)- and Blumc ovcrcstimatcs thc reduction effects of wave scattering and soil-structure interaction ior vertically incident shear waves. Zn particular, .thc strcsscs computed on thc basis of spectra rc-duccd by tau-filtering would u>>dcrcstimatc thc strcsscs that rc-suit irom thc SSI PLUS)l analysis by at least 20 pcrccnt.

                                     ~ I

4~~ ' ~ ~ - ~ ~ 4~ ~ ~ . ~ ~

 ~

The applicant has indicated that thc shear wave velocity at the site cxcccds 3600 ft/scc. Thc low-strain and itcratcd '(or strain dcpcndcnt) shear Waves velocities used in the PLUSll SGI model are not rcportcd. I rcquost that this information bc made available. In Appendix DLL-15 (Amendmcnt 53), a uni for'm. shear Mave velocity of 3500 ft/sec. 'is used. I recommend that the tau-filtering approach bc eliminated and that a complete three-dimensional soil-structure analysis for vertical and horizontally incident SH waves bc undertaken. This approach Mill havo the advantage of producing realistic estimates of. the eave scattering and torsional cffccts. The peak spectral response for the PLUSll fixed base analysis occurs at a frequency of 5.3 cps i~hilc the corresponding frequency for the axisymmetric fixed base analysis is 4.5 cps, indicating a dificrence of 18 percent,. If this diffcrencc reilects tho accur-acy with Which thc fixed base fundamental I frcqucncy can bc compu-ted, then it iiould scorn that the peak Widening of the floor rc-sponsc spectra of 5 percent on thc high frcqucncy side may bc in-sufficient. The PLUSll SSI resonant frcqucncy is 18 pcrccnt lo:~er than the PLUSll fixed base frcqucncy. This aga n sccms to indica e that the 15 percent poa1 vidcning of floor response spectra on thc low frcqucncy side is not sufiicicnt.

5. Seismic I:isk Anal scs. Scvcral seismic risk analyses for

       'thc Diablo Canyon     site have bccn pcrformccl. Thc cstimatcs obtained for the Probability of cxccdancc of thc llosgri design spectrum dif-X'cr by two orders of magnitude.          Thc applicant (Appendix D-LL 11)

P-9

~ ~ ~

     ~

j ~ d ~ estimates that tIic probability of cxcccding an 'cficctivc'ccel-eration of 0.75g in 50 years is O.l pcrccnt. Anderson and Trifuna. (Rcf. 5) cstimatc that thc probability of cxcccding thc high-, frcqucncy portion of thc llosgri design spectrum in 50 years varies from 10 to 20 percent, depending on the seismicity model considcre: Thc difference corresponding to a factor of 100 to 200 can bc ana-lyzed by considering thc following factors: (i) The applicant considers thc probability of cxccdance of an 'effective'cceleration of 0.25g while Ander-son and Trifunac use as a basis of refcrencc the 0.75g Hosgri design spectrum. The usc by thc ap-plicant of an 'effective'ather than

                                                                         'instrumental'cceleration of 0.75g reduces thc probability of ex-ccdancc by a factor of four.

(ii) Thc usc of Blumc's SAW-IV 'and SA~il-V attenuation re-lations as opposed to thc usc oi thc Trif'unac's rc-lations leads to reduction of thc probability of exccdance by a factor of t'en. (iii) Thc rest of thc diffcrcnccs corresponding to a iac-tor of 2. 5-4 can be attributed to tbc difierent'eismicity models considcrcd., llavxng isolated thc causes of thc discrepancies in risk esti-mation, I icill discuss them in detail. I have indicated that thc

           'reduction of thc peak accclcration to an 'cffcctivc'cvcl should not bc used in thc analysis of nuclear power plants. For thc pur-pose of estimating thc risk of exceeding thc llos gri design spectrum, P-10

f the anchor accclcration of 0.75g hould bc treated as actual peak acceleration. In this case, thc probability of cxccdancc in 50 years as obtained by Blume's analysis would bc of thc order of 0.4 percent (refer to Table 11.S, D-L). ll) rather than O.l pcrccnt. Thc main source of differences in seismic risl'stimates can bc associated with thc type of accclcration-magnitude-distance relation used. Thc applicant's risk analysis is based on thc usc oi the Blume's SAhf-IV and SAl)-V procedure. In my opinion, this procedure leads to accelerations which do not reflect the strong motion in the near source region of large magnitude earthqua) cs. IS one considers .the three largest earthquakes for which records werc obtained in the near source region, onc finds that the ob-served peak accelerations are three to tcn times larger than those predicted by thc SAi~! IV-V procedure (Table 2). Since thc standard deviation for peak accelerations corresponds approximately to a Sactor of two, it may be concluded that the SA'1 procedure is not valid in thc near source region'of large carthqua);cs. Table 2 indicates that Trifunac's relations lead to accurate estimates of thc obscrvcd peak accelerations (the average ratio of obscrvcd to predicted peal: acceleration is 1.07). Fig. 41-I oi Appendix D-LL 41 shows that thc usc of the SA~I procedure leads to probabilities that arc 10 times lower than those obtained on thc basis of thc Trifunac's. relations for thc same seismicity model. Thc, scismi-ll city model dcscribcd in Appendix D-LL leads then to a prob ilb 11-ity of cxcccding a peal; acceleration of 0.75g in 50 ycals of t)lc order of 4 pcrccnt.

~ g ~

                                                                          ~  ~ ~

Thc seismicity model used in Appendix D-LL ll i" based on the seismic rccurrcncc relation obtained by Smith for Central Coastal California (Appendix D-LL llA). These rccurrcncc relations arc based on thc seismicity during thc period 1930-1975 and do not in-elude thc 7.2H 1927 carthquakc in thc region. The rccurrcncc.curves as shown in Fig. 11A- 2 of Appendix D-LL 11A undcrcstimatc thc number of earthquakes with magnitudes larger than six, and arc

     ~ based on a nominal value for thc parameter b of 0.92. Additional study by Smith (Appendix D-LL 45A) indicates that a more appropri-ate value for b would be O.SS6. The parameter b which controls the relative contribution of thc high magnitude earthquakes to the tota seismicity has a'trong effect on the calculated risk. Thc usc of b O.SS6 would increase the calculated probabilities by a factor of two  (r'cfcr to Table 45.3 of Appendix D-LL 45).

Thc seismicity model considered in Appendix D-LL 11 is consis-tent with thc seismicity obtained in Appendix D-LL 41 usi'ng the geologic record of fault disloca'tion (a=3.12 in D-LL ll, a=2. SO based on 10 years record and a= 3.20 based on 20 x 10 6 years record in D-LL 41). The seismicity calculated on thc basis of the geologic record of lateral fault slip docs not include the seismi-city associated >>'ith vortical slip along thc Hosgri fault. Hamiltor (Appendix D-LL 41A) quotes a rcport by Earth Scicncc Associates in-dicating that thc .'lateral slip was probably subordinate to vcrtica) movcmcnt.'f this is thc case, thc seismicity should bc incrcascd to account ior vertical slip. Considering all thc iactors mcntioncd, it sccms that thc P-12

~ ~ probability of 10 to 20 pcrccnt in 50 years obtained by Anderson and Trifunac properly ref lccts thc seismic risl'f cxccdancc of thc llosgri design spectrum.

f v ~ t-v

     ~ ~
         ~             H
                                                .   ~

REFERENCES Seismic Evaluation for Postulated 7. Shf llosgri Eart hquakc, Units 1 and 2, Diablo Canyon Site, Pacific Gas and Electric Company. 0

2. Trifunac, hf.D., "Preliminary, Analysis oi the Peaks of Strong Earthquake hfotion-l)cpcndcnce of Peaks on Earthquake hfag>>i-tudc, Epicentral Distance and Recording Site Conditions,"

Bull. Scism. Soc. of Aner., Vol. 66, pp. 189-219 {1975). Page, R.A., D.hf. Boore, ff.B. Joyncr, and H.fV. Coulter, Ground hfotion Values for Use in the Seismic Design of thc Trans-Alaska Pipeline System, U.S. Geological Survey Circular 672, 1972.

4. Trifunac, hf.D., "Forecasting th Spectra'1 Amplitudes of Strong Earthquake Ground hfotion," Sixth li'orld Conference on Earth-quake Hnginccring, Ncv Delhi, India, 1977. Fourth'forld

5. Ncwmark, N.hf., "Torsion in Symmetrical Buildings,"

                      "onfcrence.on Earthquake Enginccring, Vol. II, A-5, Santiago, Chile, 1969.

6. Anderson, J.G., and hl.D. Triiunac, Uniform Risk Absolute Acccler4ion Spectra for the Diablo Canyon Site, Californi A Rcport to thc Advisory Committee on Reactor Safcguards, U.S. Nuclear Regulatory Conmission, Dcccnbcr, 1976.

                                              ~   ~

ll ~ i i p

                           ~,

~ i I g ~ ThlSLE l. COMPARISON OX'AXIMUMGROUND MOTIONS Peak value s M = 6.5 M = 7.5 used by Ncivma r.k1 Trifunac USCS Trifu>>ac Uc, No. 672 No 0.75 0.69 (1.29) 0.9Q 1,07 (2.00) vmax (in/s cc) 23 (48) 39 39(84) (in) 8(19) 16 12 (30)

                                ~  ~

4'cxvmark, N. M., "A Rationale for Dcrelopn>cnt of Design Spectra for Diab'.o Canyon Reactor Facili(y," Appendix C, Supplcrncnt No. 5, SER, Diablo

                   ~

Canyon Nuclear Pov:er Sta(ion Units 1 and 2, NRC, 1976. Average (average'+ standard deviation) peak motion for rock at an cpiccntral distance R = 7.5km b scd on l'rifunac, M. D., "Preliminary Analysis of (hc Peaks of S(ro>>g I art!iquakc Ground Motion - Dcpcndcncc of Peaks

                     . on Ear(I]quake Magnitude, Epicentral Distance and l<ccordi>>g Si(c Condi-tions," B.S.S.A.,       66, 149-219 (1975).      ~

Page, R, A., ct ai., "Ground Motion Values for Use in thc Seismic Dc ign

                     ~   of thc Trans-Alaska Pipeline System," Geological Survey Circular 67?, 1972,
                                          ~  ~
                           ~ ~
                                                        ~
                                                      ~

P-15

TABLE 2. 'Com arison of Recorded and Predicted Peak Accelerations SAW ry SA,4 V(4) Trifunac( ) Recorded Predicted Ratio Predicted Ratio Peak Peak Observed/ Peak Observed/ Accel. Accel. Predicted Accel. Predicted 1971 Pacoima( ) 1.25g 0.1248 10.08 0. 839g 1.49 1967 Koyna 0.63g 0. 213g 2.96- 0.766g 0.82

     ... i( )      0.80g         0. 190g       4.21              0.900g        0.89.

5.75 1.07 (1) hf=6.5, epicentral distance 3 km, focal depth 15 km. (2) h! 6.5, epicentral distance 5 km, focal depth 5 km (assumed). (3) hl =7.2, epicentral distance 10 km, focal depth 25.km.. (4)~Ys 12,000, 6 2.04,y 0 (5) s 2s p 0.50 '

C7 joo svVtl Sl(E v ~o V ~ So d

     ~ A 0

a o 5' ~ p 4>r O O ~ r< C~t

                                    ~

d pt J Iy O~ I O ql d po o I tl

                           'br                                                     po o

o.op O.os o.f o., f 5 lo ~ "0 'O ioo Frequency, cps ~ ~ ~ ~ 8 ~

                 ~ ~           F[Q. 1   DESTGi4 5P" CTRUM COMPARED 71HH PACOMA DAiVi. SP"    CTRA, 2 PERCENT DAi&PPiiG,
 ~ ~

g

                                                                                                        ~ ~

3.0 2.5 e ~

                  ~ ~

0 Dcgigll, 5$ CC ft'l l ~ If c 0) (8Lmsiic P,/%5). n

           ~1.5
         ~
           ~

0.5 0.2. 0,3 o.9 a, "I,

                                                                                                            ~ ~

0 ~ 7 (sec.) ~

 ~fQ

I-f~ r rr.. 2 r.oacr Anr.".ow ot'v:::r.7t: At, Gttt:vt.s.

                                                                                                                                       ~ r
                                                                                                           ~   ~    ~

A'0/DAC. POI lV I

                                                                                                   ~
                                                                                                                                                      ~  ~

i %OP OF CCN I Q/NiH c:F7

                                                                                                             ~
                                                                                                         /       lQ Q /if+ /~Q
                                                                                                                                                    ~ r~

85 r 0 go ~ rr Io ~ ~ ~

                                                                         )   I a ~ tw    I e
                                                                    }    i l
               ~
                    ~

I M~ .PLUSH I

                    ~, ~

JS It 4 )~ I

                                 )

I ft I )

                                                                                                                ,ssg '7"LUsH I

0 ~

                                 ~ ~ ~
                                     ~   ~
                                                                                       . f l

V 0 fo er

                                ~
                                 )   ~
                                     ~
                                       ~                                              j!                 4        ~ I
           ~   ~                                ~
                                                                                                         ~      . i ~

I e

                                                                             ~

I I l

                                                                           ~
                                                                                                                                     ~
                                           ~ =-

I

                                                  ~   ~

j )I/ I~ I 0

                                     ~ I I t                                                                                                 I  ~
               ~    ~

I

 ~

(8 0 ~

                        ~  I J                      ~ ~ I    r                                                         l1           ~   ~ \r ore i

I i. 4 ~: l

             ~

i ~~ I

                                                                                                 ~  .'

f 0.3 (.o 2.0 50 lO /o 0

1

   ~
     ~
           ~ ~
               ~
                                                          ~,)
       ~ Q
                                                   'TT    lENT

,() COetOV'rs ON SrISWIC OLSIGM LEVELS FOl( DIABLO CAliYOih SITI! IN CALII'OR'(IA by'.D. Vrit'uoac April, 1973

                                            ~  ~
                                                 ~

I

                   ~.3                ~
                                        ~

Thc following convncnts deal with seismic design criteria for thc

                                             \

Diablo Canyon site in Califor>>ia and rcprcsc>>t a brief sunnnary of my observations a>>d prclitoi>>ary co>>clusio>>s which a:c based o>> misccllancous written material and on a>>unbcr of meetings during the period starti>>g in thc summer of 1977 and endi>>g in April of 197S. Infoxtnatio>> which I had on certain aspects of this effort may bc incomplete. The general picture and the summaries of thc current status of this project ncvcrthclcss seem. adequate for thc followi>>g corrzc>>ts and rccomrtcndations. Huch has been written about dctailcd aspects of seismic design criteria for thc Diablo Canyon site and it would b" impractical to address again nun>crous points in detail and completely. Rather, I will attempt to present an overall sunnnary of what I belicvc to be unresolved problems at present, and what might bc possible avcnucs to resolve them. General Comments on thc Current In )uts and Criteria for Seismic Desi n Gc>>crally accepted <<ss(nnption appears to bc that thc SSE on Hosgri fault opposite thc plant site should bc an hi = 7.5 carth-quake. This tnag>>itudc, rcconnnc>>dcd by USGS, has bccn dctcrmincd mainly o>> the basis of thc possible lc>>gth of faulting o>> thc llosgri fault system.

2. Since hl= 7.5 at a (lista>>cc of 5- 10 km from thc site leads to large peak accc3cratio>> (about l g) considerable effort has bcc>> dcvot'c(l t.o thc a>>alyscs ldll) ch are desi g>>('.(l to show that Q-2

~

 ~
   ~ ~

these large amplitudes can a>>tl may bc rcduccd throug)t considcra-tion of t)tc fol)owing phc>>omcna: a) Scatt:ering and diffraction of hig)t ircqucncy waves from thc foundations oE different plant structures .has bcc>> proposed as a vchiclc to justify reductio>> of high frcquc>>cy spectral amplitudes (T cffcct). Thc manner in whiclt t:his .reducti.on has bccn affcctcd rcquircs unrcalisti.c assumpt:io>>s, for ex-ample, that foundation is rigid. The manner in which t)tis assumption is introduced into anal> sis if often on -sided and considers mainly only t)iose consequences of t:hc physical phe>>omena w)tie)t lead to reduction.of spectral amplitudes. Othcx co>>sequences of this phenomcno>>, for example, torsional o and rocking cxcitatio>>s of foundatio>>>>whic)t may amplify thc structural response have been, so far, either overlooked or treated inadcquatcly. T)tis has been achieved b> utilization of dynamic models for'nalysis which are so deiincd that only an incomplctc ph> sics of the problem, i.e., seismic excita-tion and t)tc structural response, can bc. considered. b) Thc term "effective peak accclcration" has bccn introduced suggcsti>>g tltat thc structure will "sce" somcthi>>g smaller t)tan actual peak accclcration. Thoug)t suc)t approach may bc uscL'ul for cart,ltquakc rcsistcnt design of ordinary structures by means oi t)ic rcsponsc spectrum tcclutiquc, thc term "cffcc-tive peak accelcratio>>" ltas not bccn dcfincd i>> a way that: would) c>>able t)ic derivation of co>>sistc>>t results by scvcral

                                                   ~
                                                       ~
       ~    ~

Q-3

diffcrcnt cxpcrts in thc field. Si>>cc thc proccdurcs for scaling Regulatory Guide ]..60 spectra arc based on maximum vibratory ground acceleration" (as dcfincd in Appendix A) this departure from routine design practices makes it diffi-cult to cvaluatc thc number and thc nature of thc conscqucnccs which would result from such an approach. c) Hypoccntral rather than distance closest to the fault has beep used to cvaluatc peak and effective peak acceleration. This assumption implies certain angles of approach of seismic wave energy. These angles o'f approach should then be con-sistent with thc extent to which "r effect" is allowed to influence the spectral amplitudes. Little or no attention seems to have been given to mutual consistency of these assumptions and in some. cases, inconsistent assumptions have been utilized. For cxamplc, deep hypoccntcr would increase the distance at which peak acceleration is evaluated, thus reducing thc estimate of peak accclcrat'on amplitudes. This would, however, alamo imply that the waves arrive towards thc foundation almost vertically. In consideration of "T effect" howcvcr, horizontal dimensions of foundations appear to have bccn used implying horizontal incidcncc of waves. d) Thc large dampi ng equal to 7'o has bccn adopted for dynamic rcsponsc calculations. Though thc apparent damping for thc comp)ctc soil-structure system, subjcctcd to carthquakc excitation ma> bc much larger tluin 7"', inadcquatc basis has been presented tn justify 7.; dangling in structural systems

     ~                                                       ~
                                                               'l

~ ~

                                  , Q-4"

'4 l only. Sclcctio>> of too large structural damping coupled with only two-dime>>siona1 or simple thrcc-dimcnsio>>al analysis of soil-structure interaction can lead to u>>rcliablc rcspo>>sc estimates.

3. At least thrcc seismic risk studies have bccn prcparcd to cstimatc thc probability of cxcccding the sclccted dcsig>> criteria at thc Diablo Canyon site (Blumc, Ang a>>d Nc>>mark, A>>dcrso>> and Trifunac).

These studies have produced results which, in some cases, differ by as much as two orders of magnitude. Concurrent >>ith the com-parisons of thcsc studies,. considcrablc cfiort has bccn devoted . to diifcrcnt details in the methodology emplo> ed in these calcula-tions. Little or no explicit effort and discussion has bccn de-voted to the models of seismicity which are essential input into such calculations, evc>> though this may rcprese>>t thc most impor-ta>>t contribution to thc discrepancies among thc results of diffcrcnt studies. I>> some extrcme cases (c.g., report by Blumc and )'iremidjian) claboratc work has bcc>> carried out, apparently in vain, to show that a particular method for scaling peak acccl-cration (Trifu>>ac, )976) supposedly leads to "too large" estimates of peak acccleratio>> irrcgardlcss oi thc fact that those results of Trifu>>ac (1976) have >>ever been used and do not rcprcscnt a basis for the dcrivatio>> of seismic risk models by Andcrso>>. a>>d Trifunac. In thc rcport by A>>g a>>d Ncwmark, substa>>tially smaller tha>> average seismicity has bcc>> assumed>>car, thc site. This may lead to a>> u>>dcrcstimatc of Lctual risk.

                                                     ~   ~
     ~ ~ ~

Q-5 I

C ~ E Recommendations A. Ground hfot ion.'. Dctcrministic approach based on thc assumption that an earthquake oC magnitude )f= 7.5 or greater >>i] 1 occur oppo-site thc plant site should bc re-cvaluatcd. This magnitude might be an indicator of thc cxtcnt of geologic faulting phenomena but it is not necessarily thc most rcliab)e basis for evaluating the nature of strong shaking close to the fault. There arc numerous examples in literature of sig-nificant differences between )I< and ))S, for example, > hich arc based on short and long period seismic>>aves, respectively. Often studies have shown that larger earthquakes may bc thought of as a sequence of several or many discrete events

      >>hich can sequentially tal'e place along a long                   fault. Finally, largest recorded acceleration, so                  f"r,  has resulted for I'he h)<  6.5 only.             For thcsc reasons,      and from   thc design vic>>-

point, I >>'ould prcfcr to adopt )I= 6.5 on Hosgri opposite thc site and not hi = 7.5.

2. Near-field source theory (not a finite element or finite diffcrcncc model of thc source and its surroundings) could be used in conjunction with the spectral analysis of strong P

motions recorded cl..cwhcre to cvaluatc the amplitudes of response spectra indcpcndcnt oC. peak accc)cration estimates or of seismic risk <<nalyscs.

G. ~lies >on.".c: h

1. Three-dimcnsio>>al soil-structure interaction analysis should bc carried out. 'I'his si>ould be done assumi>>g that thc frcc-field response spectra for design result from i>>cidcnt SII, SV or ltaylcigh waves. For Sl} and SV excitation, horizontal, vertical and 45 incidcncc a>>alysis should bc considcrcd. This approacl> would offer thc followi>>g advantages:

a. The "v effect" if prcscnt will bc accou>>tcd for correctly.

b. Torsional a>>d rocking cxcitations will be included i>>to the analysi.s correctly.

c. The proximity of the cartIiquakc source and thc fact that

               ~

the waves most likely arrive hori"o>>tally will bc accounted for correctly.

d. Thc radiation damping i>> thc soil will be introduced into analysis properly so that thc high value of 7'or struc-turcs would not bc rcquircd.

justif-L'xccpt for thc fact that 7'o dam}ii>>g is pcrmissi}ale accordi>>g to the rcgulati>>}', }',uidc ].61, thi>> high strucfur>>l darn})i>>g rccollllllcnded for thc seismic>>>>>>lysis at tl)c Dial)lo Ca>>yo>>. site has>>ot I)ccn iedd. Forced vihr>>lio>> test (avai 1>>l>lc i>> t}.S. a>>il .1>>p>>n) data, where flic et lect. of sui }-structure i>>ter>>etio>> <<>>d ili I fere>>t mode of cncr},) i>>I~>>t i>>to tl>e structure pluri>>}, n>> ex/crime>>t, relative to i>>eide>>t. <<:>> tl<>>>k~ w>>vv." is>>ot >>econ>>ted I'ur, may bc of litt]c us( )>> rs'} al> I 1,'sl1 L>>}', . LI'l. >>e( l}>> I LI>>mI) I>>} }>> ~ ( rue t urus a>>ll tht 1 j compo>>e>>}, s I or sc l sm te 'I'csI)0>>!4c c>> I cul>> C1 0>>s . Q-7

I, p C'y I'

ATTACHHENT R "IF. ~B g UNITED STATES ~ DEPARTl)ENT OF THE INTERIOR GEOLOGICAL SuRVEV-ESTIYiATION OF GROUND i~OTION PARAMETERS David H. Boore, Adolph A. Oliver III, Robert A. Page, and William B. Qoyner OPEN-FILE)REPORT 78-509 Prepared on behalf of the Nuclear Regulatory Cormission yggoGlCAL gg~,

                                                                      ~~ggi.o pARic This report is preliminary and has not been.

JUi'l 2 197S edited or reviewed for conrormity ~vith Geological Survey standards. Ll0 RAG"

                     <hqoake. The   solid Mnes       show     the 70 percent    predon        interval for the   'aqua 7.1-7.? data set of this report.                     of the points in that data
                                                            ~
                   >>tude
                -.g9>>   u           ~                                      thost
   ~\

m'I

          ~     ',>

et came from the magnitude 7.7 Kern County earthquake.

   ~ 2 f                  The amount    of disagreement         shown   in Figures    47 and 48   is not surprising
          ~

jview of the different assumptions, differ ent measures of distance, and "vs arriving at the di ffer ent curves.

                                                  ~       ~   ~              ~
              'dj fferent data sets used in   1 The h~

d jsagreement i s, as might be expected, the greatest at short di stances. '4 I'~ I .v

 'I ESTIMATION OF PEN PARAMETERS AT
                                                          'HORT DISTANCES
        \

6eneral comments. The regression lines given in a previous section of this report provide the means for estimating peak ground motion 'parameters at distances greater than 5 km f'r magnitude 5.0-5.9 earthquakes, at distances

j. greater than 15 km for magnitude 6.0-6.9 earthquakes and at distances greater v

than 40 km for magnitude 7.0-7.9 earthquakes. Unfortunately, most of the F daniage from earthquakes can be expected to occur at shorter distances.. Attempts have been made, as described in the preceding section, to provide

 %1 curves      for estimating at shorter distances.               For reasons given in the 1

Preceding section we do not have complete confidence in those curves. Me will yC not venture our own set of curves, but will discuss briefly some of the

.r.'         considerations bearing         on ground       motion estimates near the source.            Further
  ~

discussion of these questions in greater depth is given by Boore (1974).

'-r m                     There have been a number          of studies using simplified          models   of the fault;ing process to set limits               on    the ground motion at the       fault surface (Housner, 1965; Ambraseys,              1969; Brune, 1970; Ida, 1973).            Brune's (1970) near source model assumes           that rupture occurs instantaneously over the fault

I I n') pile. peat particie ve1oty is proportional to the sts drop and aqua s >00 cm/sec for a stress drop of 100 bars. The peak acceleration is infinite s~ q f all frequencies are included, but if frequencies above 10 Hz are filtered out of the acceleration pulse the peak value is 2 g. This is a useful model for relating gr ound motion to the physics of the rupture process,

'ut             it does      not give   firm   upper   limits. An   argument can be made       for larger
   ~tions              if one   takes rupture propagation into account (Ida, 1973; Andrews, 1976)..             Furthermore, the peak values of ground motion may represent                                     localized hi19 h stress drops as Hanks and Johnson                    (1976) have suggested         for  peak acceleration.                Such   localized stress drops might easily exceed               one                   kilobar.
 ..:":-..', The peak            acceleration at the surface is limited by the strenoth of near surface materials as has been pointed out by Ambrasey (1974).                                For                   sites near the source underlain by                  soil material of       low strength,     this factor                      may  control the value of  peak   acceleration.      This consideration       may   also apply to rock
                  ~~

sites if the rock is sufficiently weathered. Determination of tho limiting acceleration, however, would require reliable measurement of the dynamic, in h ~ k. situ strength of the soil at a particula'r site. In the absence of adequate measurements one must presume that the acceleration could be at least as large as 0.5g, which was recorded on a thickness of more than 60 meters alluvium at station number 2 in the Parkfield earthquake of'ater-saturated

                \

(Shannon and Wilson, Inc. and Agbabian Associates, 1976).

    ~     ~

e In the case of peak displacement, as pointed out by Trifunac (1976), I if

 ,one assumes                no overshoot, the peak is limited to less than one half the                                     static
     >slocation amplitude.                  The  latter is    known    for  many  historical earthquakes
  >>d           may be      estimated as     a function of magnitude (Bonilla             and Buchanan,                     1970).

The accelerogram recorded at Pacoima Dam during the San Fernando R-3

                                                                                                         \              1~ m
     <earthquake           has major sign%>cance         for   near     source groundWotion estimates.

The instrument is located only 3 km from the rupture surface at a rock site

     ~~ere          the topographic       relief is   severe.       The peak     recorded horizontal I

acceleration is 1.25g, velocity 113 cm/sec, and displacement 38 cm. This is tpe only accelerogram ever recorded within 5 km for an earthquake of magnitude as large as 6.4, and as such ought to have strong influence on estimates of near-source ground motion. The possibility of topographic amplifica ion needs, consideration. A two-dimensional finite-difference study by'Boore (1973) suggests that the acceleration may have been amplified by as much as 50 Percent but that th'e velocity and displacement were relatively unaffected. Given these considerations, it would be difficult for us to accept estimates less than about 0.8g, 1'IO cm/sec, and 40 cm, respectively, for the mean values of peak celeration, veloc't d ~em ~tt rock sites within 5 km of fault rupture in a magnitude 6.5 earthquake. Me recognize that these numbers

 ~

iepresent one earthquake with a particular focal mechanism and that estimates are bound to change when more data becomes available. >le presume that the

   ~  P. ~ s  s.

statistical scatter about the mean will be at least as great for the near-in sites as at the greater distances where data is available. The accelerograph at Pacoima dam was only 3 km from the nearest point on m t'he rupture surface, but the nearest point was not the source of the peak

     >>tions.             As  noted previously the source            for the    peak    velocity     and    for the Peak          acceleration are different points             on   the rupture surface separated by Perhaps           as much as 20 km (Hanks,        1974; Bouchon and          Aki,,1977).

~

            .       Above magnitude       6.5 there are essentially no data               for estimating the effect of magnitude               on  near-fault    peak    acceleration, velocity            and 4isplacement,             other than the     static fault offset divided               by 2 as a bound on

h I g /,

           ~\

I the peak wrath d~ magnitude-sp aoement

                                          ~

Hanks and Johnson Conservatism

                                                                           ~

{1976) presented

                                                                             ~
                                                                                  ~

requ ires the presumption or a some set of peak acceler [norease at. source distance of approximately 10 for earthquakes in the t'ata km magnitude range 3.2-7.1. The only data point above magnitude 6 5 was for th imperial Valley earthquake of 1940 which they assign a magnitude of 7.1 in contrast to our value 6.4, so the data set can be applied to magnitudes greater than 6.5 only as an extrapolation. The data set shows some dependence of peak accelerations on magnitude, but Hanks and Johnson argue that the data are consistent with the idea of magnitude-independent source properties. The data plotted as the logarithm of peak acceleration against magnitude can be fit by a straight line with a slope equivalent to an increase by a factor of 1.4 per magnitude unit. This should not be used for extrapolation beyond ccgnitude 6.5, however, because the data set was deliberately chosen to represent relatively high values, and thus the slope of the line fitting the data may not be the s arne as the slope of the line representing mean values or, for. that matter of

                                 , o    the 11ne representing values for any fixed probab                 lity.
            '..':-Atsites other than rock            sites accelerations might          be  less because of the limited stren g h       t   of near-surface materials, but,           as   previously noted, determinin g ho w much less would requ>re dynamic,                  in-situ measurements of soil properties.          The am plif~cation      of  peak  velocity at soil sites compared t                      k
      ~
        'sites:may not         b e so   great close to the      fault   because    of the energy lost in nonlinear soil deform    eformatlon, but numb:.ical modeling (Joyner and Chen, 1975) demonstrates         the  possibility of amplification of velocity                by as much as 30
             <<ent      even under cond)talons        of intense deformation.           The  possibility of greater       am p lification      cannot be excluded.      Anplification of displacement at o<1    sites should       be  expected close to the       fault, -as at greater distances,                if

                                                                       . ~

the soil column is sufficiently thick. ACKNOWLEDGMENTS We are grateful to R. P. Maley for assistance in obtaining information 0n strong motion recording site conditions and to A. G. Brady for unpublished'trong motion data. R. B. Natthieson, T. C. Hanks, and A. G. Brady reviewed the manuscript and suggested improvements. l

~ "\ I
~1  ('

1)~'h'~ ~ I~ g

 \~ ~

P C ~ 1' I+ \

             ~;'.ZI '
        ~  ~

R-6}}