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Faults at Getr Test Reactor Site,Vallecitos Nuclear Ctr, Pleasanton,Ca
	ML19310A252
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Site:	Vallecitos File:GEH Hitachi icon.png
Issue date:	04/30/1980
From:	Brabb E, Herd D; INTERIOR, DEPT. OF, GEOLOGICAL SURVEY
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{{#Wiki_filter:.. I FAULTS AT ~EE GE'iERAL ELECTRIC TEST REACTOR SITE VALLECITCS NUCLEAR CEiTER PLEASA!iT0!i, CALIFORNIA l i i A Summary Review of Their i Geometry, Age of Last Movement, Recurrence, Origin, and Tectonic Setting and The Age of the Livermere Gravels by Darrell G. Herd and Earl E. Brabb .i U.S. Geological' Survey Administrative Report April 1980 4 80060604M f

SUMMARY

New geologic data provided by consultants to the General Electric Ccmpany relative to faulting and landsliding at the General Electric Test Reactor (GETR) near Pleasanten, California, has been evaluated; information provided previously by the consultants has been reexamined. We continue to support our previous conclusion that the arguments for landsliding have no basis in fact, and that the test reactor is within a sene of active thrust faults. We concluded previously that the number, location, length, width, geometry, and age of these thrust faults have not been determined adequately, and therefore that the potential for future surface faulting or vibratory ground motion at the reacter could not be adequately or reliably assessed. None of the new informatien provided by the General Electric consultants has changed this cpinion. However, inasmuch as the consultants have provided informatien en fault potential that we believe to be incorrect, and inasmuch as a decision regarding reactor safaty could be made without obtaining the additional geologic information we feel is necessary to assess fault potential, we provide herein a preliminary interpretation of some of the critical fault parameters. 1. The General Electric Test Reactor (GETR) lies within a zone of thrust faults. Three individual fault strands have been discovered near the reactor, two of which project beneath it. One thrust fault crops out at the base of the hills behind the GETR, approaching the reactor to within 350 ft. This zone, the B-1/B-3 rault, dips 9 -31 NE. away from the reactor into the hills. Two subsidiary thrust faults, B-2 and H, surface respectively 900 ft and 3,200 ft southwest of the reactor. The B-2 and H 0 0 faults dip northeastward beneath the reactor at 25 and 27, respectively. If the faults do not change dip at depth, fault B-2 passes 500 ft beneath the reactor, fault H about 1,200 ft below the reactor. i

2. The absence of faults opposite the GETR in the B-1 trench 280 ft n'orthwest of the reacter does not preclude the existence of faults beneath the GETR that either do not extend north to the trench, or that are older than the 70,000-130,000-year-old alluvium in the trench. 3 Both the B-1/B-3 fault and the B-2 fault, and possibly the H fault I displace the modern soil profile. The most recent fault movement is bellaved to have occurred since 2,000-4,000 B.P. 4 During the latest faulting episode, there was 2 to 5 ft of thrust movement on the B-1/B-3 fault, 3 ft of thrust move =ent en the B-2 fault, 1 and 1.5(?) ft of thrust movement en the H fault. 5. The displacement history of the 3 thrust fault strands is similar, suggesting that faulting occurred si=ultaneously on all 3 stra-ds. If so, the cumulative movement during the last faulting episode is 6.5(?) ft to 9.5(?) ft. 6. There have been at least 2 episodes of movement en faults B-1/B-3, B-2, and H during the last 70,000-130,000 years. There may have been as many as 4 to 5 slip events on fault B-1/B-3, and 3 on fault B-2 if the most recent offsets are characteristic of the amount of movement that occurred during past faulting events since 70,000-130,000 B.P. 7. An average slip rate of 0.0004 ft/yr best fits the cumulative uit displacement / age data.

8. - The 3 thrust faults at the GETR site cannot be explained as part of an ancient landslide.

a. The postulated landslide complex could not be documented where trenched. 11

r b. Faults in the hills above the CETF that have been inv:k:d a: =cvement planes of an ancient landslide strike at the wrcng angle fcr a deep-seated slump bicek, are not traceable laterally frc: ene hill to the next, and see= directly related to small-scale, shalle. landsliding or tectonic =ove=ent. c. There is evidence for Holocene and =ultiple late Pleistocene offsets on the thrust faults at the GETR site. Faults in the headwall scarp area of the pestulated ancient landslide display no history of cultiple or Holocene displacements. 9. The faults at the GETR site are parts of an active tectenic thrust fault, the Verena fault. Tectenic faulting is required to explain: a. Recurrent fault =cve=ent. b. Nearly perpendicular discordance in strike between the riddle congle=erate unit and upper = ember of the Liver =cre Gravels about 2 miles northeast of the GETR. c. Drastic thinning of the upper member of the Liver: ore Gravels eastward across California Highway 34 d. Continuity of thrust faulting outside the area of the postulated ancient landslide. Steepening downward of the dip of the thrust faults with depth. e. 10. If the alluvial deposits exposed in trench 3-1 extend beneath the GETR, the reactor rests on beds that are older than 70,000 to 130,000 years, but younger than 300,000 years. If the reactor rests directly on Liver: ore Gravels, it is on deposits that are older than 300,000 years and younger than 5,000,000 years. l l iii i

s en.,--.,-- wwas 4 Les 4 Q Page Centents------------------------------------------------------------- iv Figures-------------------------------------------------------------- v Tables---------------------------------------------------------------viii Introduction--------------------------------------------------------- 1 U. S. G eo l o g i ca l S urvey R ev i ew -------------------------------------- 2 Fault geometry------------------------------------------------------- 3 Ccnfiguratien of faults beneath the GETR and adjacent hillfront---- 5 A g e o f las t fau l t mo ve men t ------------------------------------------- 7 ESA interpretation: No fault offset in last 8,000 to 10,000 years-9 USGS interpretation: Last fault movement since 2,000-4 000 B.P.--- 16 Recurrence of faulting----------------------------------------------- 21 Slip rates----------------------------------------------------------- 33 Crigin of the fault surfaces-----------------------------------.----- 33 Cre s c e n t - shap ed amp h ith ea t er--------------------------------------- 33 D i s t u r b ed b e d d in g -------------------------------------------------- 33 Pos tulated rotational slump blocks--------------------------------- 45 Origin of faults in F and G trenches--------------------------------- 47 Continuity of headwall scarp of postulated landslide complex------- 50 Timing of =ovements------------------------------------------------ 52 Anomalous geologic relations and thinning of section--------------- 52 T ec t en i c f ra m e wcr k --------------------------------------------------- 64 L ive rmo r e ea r th quak es o f 19 8 0 -------------------------------------- 67 A ge o f Liv erm o re G rave ls --------------------------------- - ---------- 69 References cited----------------------------------------------------- 75 iv

et-6

L"U.n. e -w Figure 1 Map of thruct Tsults and trenches near the OIT3 Site-----

4 2. Inferred configuration of fault: beneath tne CITR-------- 6 3. Dip of the 3-1/3-3 fault at trench T-1------------------- 8 4 Scils at the ;272 31:2----------------------------------- 10 5. Reproduction of leg of trench B-1, showing soil stratigra;hy-------------------------------------------- 11 5. Reproc a::len of leg of trench 3-2, shewing soil

trati.rathr--------------------------------------------

12 7. 3adiccarocn dates Of n:dern soils in trenches 3-1 and 3-2-------------------------------------------- 14 3. Curve showing effect of ad=ixture of " dead" and ":c i;r ' :a.4 b en en radi:carb en ages-------------------- 15 9. Seinterpreted leg of trench 3-1, showing continuation cf thrust fault inte Ae horizon------------------------ 17 10. Beinterpreted leg of trench B-1, showing continuation of thrust fault into Ae and A12 hori ens--------------- 18 11 Radiocarben dates of odern soils in trenches B-1 and B-2, arranged by horizon and locality 20 12. Anount and age of ovenent observed on faults in trenches 3-1, B-2, 3-3, and H-------------------e>----- 22

13. Pictorial chronology of geologic events represented in trench B-2 (fig. 6)---------------------------------

24 14 Average slip rate on faults at the GETR site------------- 34

15. Evaluation of evidence for postulated large-s cale landsliding in the GETR area---------------------

35 v

16. Plan of crescent-shaped ridges near the GETR------------- 36

17. Differences in strike of bedding near the GETR-----------

38 18. Bedd ing at titudes in th e GETR area----------------------- 39

19. Ane=alous a t t itud es in trench G-1 ------------------------

40 20. Anomalou s at titudes in trench G-1------------------------ 41 21. ' dell-bedded sequence in trench F-12 for which no a t ti tud e s ar e p rov id e d --------------------------------- 42 ' y~ 22. Rose diagram showing different interpretations of bedding s t r ik e in tr e nc h F ------------------------------------- 43 23 Rose diagram showing different interpretations of bedding s t r i k e in tr e nc h G------------------------------------- 44 24 Attitudes measured by E. E. Brabb in late 1978----------- 46 25. Dip of bedding in the hillside are northeast of the GETR 48 26. Character of sheared surfaces in the vicinity of the GETR 49

27. Faults in the central part of trench G-------------------

51

28. Timing of movements on shear surfaces in the

" ic in it y o f th e GETR----------------------------- 53 29. Geologic map of the GETR area---------------------------- 54

30. Location of cross-sections near the GETR-----------------

56

31. Different interpretations of the stratigraphic interval -etween the middle conglomerate of the Livermore Gravels and gravel beds within the upper grave l member in se c tion CC ' ---------------------------

57

32. Different interpretations of the stratigraphic interval between the middle conglomerate of the Livermore Gravels and gravel beds within the upper l

gravel member in section DD'---------------------------- 58 { l vi i 1

33 Different interpretatien of the stratigraphic interval between the middle conglomerate of the Livermore Gravels and gravel beds within the upper g ravel memb er in s ec ti on EE ' --------------------------- 59 34 Different interpretations of the stratigraphic interval between the middle ocnglomerate of the Livermore Gravels and gravel beds within the upper g ravel =emb er in s ec tion FF ' ---------------------------- 60

35. Stratigraphic interval between the middle conglomerate of the Livermore Gravels and gravel beds within the upper grave l member in se c tion GG ' ---------------------------- 61 4

36. Stratigraphic interval between the =iddle conglomerate of the Livermore Gravels and gravel beds within the upper gravel member in section HH'----------------------------

62

37. Map of principal recently active faults in the San Franc is co Bay region ------------------------------------ 65

38. Tec tonic framework of Livermore Valley--------------------

66

39. Map showing location of the January 1980 Livermore earthquakes and the accc=panying surface rupture on the Greenville and Las Positas faults-----------------------

68 l vii

1 .I 15, .i 1 TABLES l Table 1 Reperted ne: of modern soil hori:On: at the CI R------- 13 i 4 l I + 1 t ,I 1 1 I. i 1 J 4 i 1 9 4 2 t I t j viii L.

INTRCDUCTICN In Septe=ber 1977 the U.S. Geological Survey published a geologic =ap (1) which relocated the Verona fault to within several hundred feet of the General Electric Test Reactor (CETR) at Vallecitos Nuclear Center, Pleasanten, California. The fault was shown to displace gravels of Pliocene and Pleistocene age and was considered potentially actf ie. Publication of the map coincided with Nuclear Regulatory Cc=:ission staff review of General Electric Cc=pany's relicense petition for the GETR. Because of the possible hazard, the Nuclear Regulatory Commission requested the General Electic Cc=pany to evaluate the fault. Two trenches, T-1 and T-2 (2) were excavated by Earth Sciences Associates (geological consultants to the General Electric Cc=pany) across the tapped trace of the Verona fault in October 1977. In beth trenches imbricate, gently northeast-dipping thrust faults cutting Pliccene-and Pleistecene-age Livermore Gravels and younger, overlying colluvium were encountered. Progressively greater offset of successively older buried soils by the fealts indicates that there has been recurrent movement on the faults. The last episode of displacesant on the faults was latest Pleistocene or Holecene. The Nuclear Regulatory Co= mission staff concluded that the Verona fault apparently existed, that it should be considered to be capable, and that it presented a potential surface faulting hazard and high ground acceleration hazard to the safe operation of the reacter (3). On October 24, 1977, the Nuclear ) Regulatory Cetmission ordere d the General Electric Company to bring the l General Electric Test Reactor into a cold shutdown condition, and to show cause why the suspension of activity under Operating License No. TR-1 should f not be continued. 1

General Electric contested the shutdown of the reactor, arguing that the faults at the GSTR site are not tectenic, but rather are shears at the sole of an ancient landslide. During the last months of 1977 and =ost of 1978 a nu=ber of trenches and boreholes were excavated near the GETR to explore the extent, age, character, and crigin of the faults. The findings are su==arized in the reports en the geology of the General Electric Test Reactor site prepared by Earth Sciences Associates (ESA) and their consultants (2, 4, 5, 6, 7). U.S. Geolegical Survev Review Cn December 9,1977, the U.S. Geolcgical Survey was requested by the Nuclear Regulatcry Co==ission to assist in the review of the potential for surface faulting within the i==ediate vicinity of the GETR. Geological Survey personnel subsequently participated with Nuclear Regulatory Cc==ission staff in the exa=ination of the geology of the GETR site, and in the review of geologic docu=ents submitted to the NRC by the General Electric Cc=pany. On Septe=ber 5,1979, the U.S. Geological Survey submitted to the Nuclear Regulatery Cc==issien a review of the geologic data relevant to the General Electric Test Reactor (8). At a subsequent meeting of the GETR Subec==ittee of t?e Advisory Co==ittee on Reactor Safeguards held in San Francisco on November 14, 1979, General Electric made public new geologic infor=ation en the GETR site (9). Because of the i=portance of these new data and other new information obtained by the U.S. Geoles. cal Survey, we decided to sub=it to the Nuclear Regulatory Co==ission this additional review of faulting at the GETR site. 2

1 l TAULT GECMETRY Trenching has revealed that the General Electric Test Reactor lies within a zone of thrust faults. Three individual strands have been discovered near the reactor (fig. 1): a principal :ene of imbricate thrust faults crops cut at the foot of the hills behind the GETR; two apparently chorter faults lie southwest of the reactor. The fault :ene at the base of the hills behind the GETR, herein referred to as the B-1/B-3 fault for its exposure in those trenches (6), censists of a group of northeast-dipping thrust faults; it is coincident with the Verona fault of Herd (1). The :ene dips fren 9 to 17 NE. near the GETR. and 14 0 C U 0 and 31 NE., respectively, scuth and north of the reactor (trenches T-1 and T-2). Pliocene-and Pleistocene-age Livermore Gravels in the upper plate (the hills northeast of the GETR) have been repeatedly ditplaced southwestward across younger late Pleistocene and Holecene colluviu: and alluvium at the base of the hillfront. The uppermost modern soil is offset by the faults. Progressively greater offset of successively older buried soils indicates that there has been recurrent movecent en the ene. Slickensides on the fault planes in trenches near the GETR indicate that latest fault cove =ent has been essentially dip-slip, with s=all ec=ponents of lateral displace =ent (fig.1). About 900 ft southwest of the GETR, a subsidiary line of thrust faulting (B-2) was discovered by the extension of trench B-1. Fault B-2 dips 25 NE., beneath the General Electric Test Reacter. Livermore Gravels are thrust over late Pleistocene and Holocene colluvium / alluvium near the surface. The fault similarly offseis the modern soil; there is progressively greater displacement of older buried soils with depth. The fault has been traced laterally at least 1,160 ft in small trenches excavated north and south of trench B-2. The fault continues at least 760 ft south of trench B-2, and is believed by ESA 3

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(6) to. end about 360 ft nceth of 3-2. However, several of the trenches excavated to encounter the fault ncrth of trench 3-2 may be located too f2r ea:t to find the probable northern centinuation of the 3-2 fault. Not shcwn in ICA's cross sections (e.g., Geologic Sectitu 7-7' in 6) of faults beneath the GZTR is a third line of thrust faulting discovered near Building *02, ateut 3200 ft couthwest of the G2 2. This fault, disecvered in the H trenches, dips 270 NE., towards the reactor. In a =anner similar to that of faults 3-1/3-3 and 3-2, fault H iccally thrusts Liver = ore Gravels over younger late Pleistccene and 2clecene(?) alluv.un and celluviu=. The =ap extent of fault H i unkncwn. The faul: strikes directly toward Building 102. and may centinue scutheastward along the fcct of :he small hill next to the

building, to Ccnfiruratien *f 71 tit 2 3=r.?a'h the OET' ~ ~ f I"*10e*: "illfrent 3ecauce of their ncrtheart dip, fault 2-2 and fault H project beneath the reac ter ( fig. 2). If the faults do no change in dip at depth, fault B-2 passes abcut 500 ft beneath the foot of the GETR, fault H approxicately 1,200 ft below the reacter. However, there may be other faults that actually surface beneath the reactor. No systematic search for faults at the GETR site has yet been undertaken. The absence of faults opposite the GETR in the B-1 trenen excavated 280 ft north of the reactor does not preclude faults that could surface beneath the GETR, but either do not extend north to the trench, l

or are older than the geologic =aterials exposed in the trench. The low dip of the faults has been interpreted by ESA (6) as supportive evidence that the faults are part of a landslide, rather than tectonic in origin. The surface of rupture of a slu=p block should be generally concave uoward and connect to a scarp area near the head of the slide. The dip of a 5 1

CROSS SECTION OF GETR SITE w er. [ 1000 ft ,I 4 350 ft->l 200-TRENCH B-l -TRENCH B-27 GETR D 4 a FAULT FAULT B-2 B-l/8-3 '00-500 ft r O-FAULT H 1200 ft -10 0 - 0 200 400 feet O 100 200 meters

400, Y

N Figure 2. Inferred configuration of faults beneath the General Electric Test Reactor. Cross section of GETR site constructed along trend of trench B-1/B-2 (N.44 E.). The faults are assuned to maintain dip at depth. 6

tectonic thrust fault =ay re=ain the same or it =ay steepen dcwnward. Only 3 boreholes (fig. 3) have oeen drilled to exacine the dip of the thrust faults with depth along the hill front. These holes, dug at trench T-1, suggest that the thrust fault zone at the hillfront steepens frc: 100 at the surface to 0 35 40 with depth, as would be expected if the fault is tectonic. In ESA's most recent report (9) the icwer: cst thrust in trench T-1 is shown as centinuing nearly horizontally into the hillfrent. The lowermost thrust fault of trench T-1 is joined at BH-3 to a " shear zone (?), indistinct contacts, grad. over 1-2"..." (2, leg of 3H-3), rather than to the " sheared contact ene, well developed slicks, shear zone 1-6" wide, 2-3 clean, anastemizing planar breaks..." abcut 15 ft deeper in berehole BH-3 The thrust in T-1 acre probably should be joined to that lowermost =ajor shear in 3H-3, rather than to the " shear zone (?)" above it. AGE OF LAST FAULT MC7EMENT An accurate determination of the age of last movement on the thrust faults at the GETR site is critical to deter =ining the origin of the faults near the reactor. General Electric and its consultants state that the faults are part of a great landslide that was last active during the last glaciation (10,000-70,000 B.P.), when the climate =ay have been wetter in coastal California. The slide purportedly is new inactive in the drier climate of the present time (the Holocene). A Pleistocene age (>10,000 B.P.) for the last movement en the faulLs wsuld be cc=patible with the inferred landslide. Any evidence for renewed movement en the faults in the last 10,000 years (the Holocene) would not support the consultants' landslide =odel, but would be another line of evidence for tectenic faulting. 7

DIP OF THRUST FAULT AT BASE OF HILL Southwest Northeast /~j-BH-3 TRENCH T-1 BH V '~.~,, g K BH-3__ '_/y' 7===- _ s&: g / x h' ~N. ..soo - 600-N. ~ 2-q ~ ~ w% - - c ~m~ / ~. ~ hpping ~ ' -" N: m.__ =

N4' b

7 20' N. Dipping'. u \\ i$3 cc 4' SW. -- 10 NE. . \\\\ .I tal ,/ / x Desenbed as shear 20na with weli-Describerl us developeci slicks. shear zorie(?) with Dipping 35 -45 NE. indistinct contacts 500-0 60 100 feet 500 t.... -. -,3 .- 4 A// stieors depicled as dipping north. t'igure 3 Dip of the B.1/ti-3 fault at trenen T-1. Fjgure mdified from reference 9, in which the fault. was portrayed as low-dipping or flat-lying with1r. the hillfront. It is wie 'J ikely that the fault steepens to 45

ESA Interpretatien: "o Fault Offset in Last 8.000 to 10,000 Years To derive the age of last sevement en the thrust faults at the GETR site, it is necessary to review the relationship cf the faults to the surficial soil ( fig. 4). At least 2 of the 3 thrust faults near the GETR site (those seen in trenches 3-1/3-3 and 3-2, and possibly H) displace part of the modern soil. The logs of trenches 3-1 and 3-2 (figs. 5 and 6) show that the B horizons of the =odern soil are offset at both trenches. In trench B-1 the IIIBt (incorrectly labeled III13t) and !7321t horizons are shown as cut by faults. In the leg of trench 3-2, faults displace both the 31 and B2 horizons of the cdern soil. The overlying A hori: ens (the A1 and Ae horizons) are not shown to be dicplaced in either trench. Earth Sciences Associates (6, p. IV-8) state that the cambic horicens of the modern soil--the 31 of the modern soil (6, fig. A-6)--are not offset, even though the B1 in trench B-2 clearly is faulted. In a discussion of fault displacements of soil-stratigraphic and gec crphic =arkers (6, Appendix B) the A2 or Ae horizons (albic horizons) are reported to be offset in both trenches. Whatever the fault / soil horizon relationship, the A1 horizons in both trenches are supposedly intact and unfaulted. In a discussion of soil development and soil radiocarbon dates (6, p. A-18 - A-25) the A1 horizons are judged to be about 8,000 years old. The modern soil is supposed to have started forming shortly after 17,000-20,000 B.P. in colluvium deposited atep the stoneline. In a stratigraphic-like progression the modern soil is reported to have developed horizon by horizon, younging upward (Table 1). The argillic horizon (Bt) began 9

s _. m- _ ~. ___.. O Decomposing uagenic spettes, s .811 Mineral busisons et or ed acent to sus face. generally des k color and lovv chsuena seul containerig I i .412 Mulhc Epspedon percent of snose urgenic n.atter. Sutal wiled si.asnly on dif ferences an stune, root and pore con-ail tent; e.ullucelly color. Olsen cun.ubc nus n.odern drain.ges. Modcres Lulusn Al fic) ' Alt,ec florison Lluvaal horison typtilsed by loss of laun unides drid clay; has "bleectied" appearen6e,Isequently supsrimposud on undsrly6sig Bi hus asun, or

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= i 3 o i \\ m i, 0

t. t. i o,.

g~. n 2 \\. tg :\\.. 5, = t, l m. o 'it... i. .t-ca x g g l l.' ).A.%~, 3 t '..s..~.,.i ~. - '! ',\\- uc S C ,1 : s - .. _, ; a c .m o - 4 , A.:. , l,\\ 8 p s a .p '> i \\s g l s a s "\\ -t i ~ = s u y \\. 1, P \\ \\ \\ ~' t \\ %~ I '. ', ', i. t '. ie i 2,' i j 't; ; i.\\, \\- ? l s ,l i } +.h., s \\. i Q I, .3.' i f.. '\\ \\ \\ \\. '. \\ " \\, =* l + \\ =i i a )\\\\ \\; .\\ 3 g 1., ', i/ .t - a - i we i i. t. 'z n

s. ] -..

N a = C -- t ?,u,l \\\\. \\., o. -a i

n. s.

1 i c, a n \\.\\ vm' su l s. t\\i .\\ 't.,. 'i ~'~ ti \\i _,. - i l! f-- * \\. \\ '. \\ ' ' g.,* \\ < j? g, -

4. 3 6

x nn n,, J.\\-; ii it i \\ \\ '3 ) l \\ }t " \\,h v. -f ~ a t t )1x. t t. ; z s ~ i s i s-g o_ t.- \\."g. qp-ll ~~ t q 's ~ 1 \\ Il I + - t, s m! = =. I .t \\ {,, \\ '..iL :) o I- 'ht. j v.> \\- l e m 1 m _,, m I 1,

\\

'~, '

f 9 \\ e.'\\. '. \\. \\ t '.

\\

\\ i s s t-q m i ~ I ' t "I \\, 1., 4 + -i . { d _. \\.._.. - e , 'l u,. .I = .l \\ \\.) y; i a t I .m i t s \\ \\ =i ~ \\o 1. \\ o u et u ti g 1 i -- ; k I ~. 'L.} '"" 'b \\ j s '. _ ~ i~ i. t. \\ \\ = .i - i s .. f 9 8 9 ) ) a f M: a = a a 2 a a s t u r. i (lllJ) Hid10 w ls E l i 1.'

Table 1 Reported ages of modern soil horizons at the GETR (5) Ace assigned according to reference Herigen

p. A-15

p. IV-8

p. A-23 A1 All horizons A2 or Ae early Holocene? (<10,000 B.P.?)

10,000-20,000 B.P. >8,000 B.P., B1 <15,000 B.P. 8,000-10,000 B.P. and more Bt 10,000-17,000 B.P. cr likely in the 20,000 B.P. range of 12,000 to 15,000 B.P. for=ing shortly af ter 17,000 B.P.-20,000 B.P. The overlying B1 (cambic) horizon formed in "somewhat less than about 15,000 years" (p. A-15). The leached A2 or Ae (albic) hori:en was supposedly "one of the last (early Holocene?) weathering events, preceded by development of the modern weak argillic (Bt) horizon in latest Pleistocene (stage 2) time" (p. A-15). Twelve radiocarbon dates (alkaline soluble and insoluble) from the A1, Ae, 31, and Bt heri: ens of trenches B-1 and B-2 (fig. 7) yielded =ean residence ages of about 4,600 and 2,000 radiocarbon years at trenches B-1 and B-2, respectively. R. J. Shle=cn (6, p. A A-25) concluded that because of continual contamination by " modern" carben during the last 15,000 years these soil ages as determined were too young. Pointing out the effect of " modern" and " dead" carbon admixtures en radiocarbon age (fig. 8), Shlemon noted that these horizons are probably at least 8,000 years old and more likely in the range of 10,000 to 17,000 years. ESA (6, p. IV-8) concluded that there was no fault offset within the last 8,000 to 10,000 years, and that the last offset occurred sometime between 10,000 and 17,000 years ago. 13 l

ltudiocurbon 1)ntes, Modern Soils,_ Trench 11-I/li-2,.Gl."I'lt I.nb 11o. Sainple I.ocution Age (M itT) Soil llorizon Alkuli Soluth Alkali lusoluble G X-6006 Trench 11-1, stu. 69.5, 4,310 1300 2,440 t lii0 tillit depth 2.3 f t. GX-6007 Trench Il-1, sta. 73.0, 3,045 1 215 1,600 t500 il Ae-In g depth 1.6 f t. GX-6008 Trench 11-1, stu. 73.0, 4,240 t195 1,105 ilus 111111 depth 3.3 f t. G X-Gull Trench II-2, sta.119.0, 2,1 6 0 1 19 5 1,175 1210 li j depth 2.0 f t. GX-6012 Trench 11-2, stu.119.0, 1,215 i115 1,565 i175 A j.2 depth 1.0 f t. G X-6013 Trench 11-2, stu.103.0, 1,240 i130 2,180 1195 li g depth 1.2 f t. 1) Itudiocarbon dating by ueocliron 1.uboratories (GX); replicate saniples froin Trench 11-1 (Teledyne isotopes) yielded insufficient organic inalter for fulvic and huniie neid fractionation. 2) All dates are incan residence tiene (Mitt) from bulk saiuples; orgunic inutter recovered for counting lens than 1 percent; see text for discussion. 3) See detailed soil profile description and measured sections; text. Figure 7. Itadlocart,cn dates of inodern soils in t.renchen B-1 aunt H-2. ,ilept oduct.lon of Table 1 or eference 6,i.. A-19.

o Q "Mooern

Caroon 30-50 %

20% ,og ?, 1s% I i / / / 2. I / / h l l /

20-

/ / / // ,3s / / / = / / } i f. < - w f j l/ / g rt ' ,/ / /,/ /

4 10-

/

Dead" Caroon 5-

/ . t / '5 5'O ts 20 25 30 Apparent IdC age tvears x 10001 l Figure 8. Curve showing effect of admixture of " dead" and " modern" carbon on radiocarben ages. Colored area represents range of " modern" carbon contamination that would be required to make samples actually 8,000-15,000 years old appear to be only 2,000 4,000 C-14 years old. Reproduction of Figure A-11, reference 6. 1 i 15 l

"200 !nterpretation: Last Fr:lt McVecent Since 2.000 4.000 3.?. We disagree with the ICA assessment that there has been no fault =ove=ent in the last 10,000 years at the GETR site. We believe that evidence gathered by ESA is both permissive and supportive of fault displacement in the last 2,000 to 4,000 years. We observed that the Ae, 31, and Bt heri: ens of the =cdern soil were offset by faults in trenches B-1, B-2, 3-3, and A, as well as in trench T-1 (2). This soil / fault relationship is incorrectly portrayed in ESA's logs of trenches B-1 and B-2 (ce: pare figs. 5 and 6 with 9 and 10), and c=itted altogether frc= the legs of trenches A and T-1. We believe that the A1, A2 or Ae, 31, and Bt horizons are not more than 4,000 years old and that they are still developing. The modern soil is interpreted by ESA as being successively older with depth. However, soil horizons of the sa=e solu = do not develop independently with ti=e--that is, the 3 hori en forming before the A heri:en. Rather, horizons of the sa=e soil grow and =ature as an integrated whole. The process rese=bles sieving. At the surface, organic =atter and mineral =atter accu =ulate in the A hori:en. That hori en is usually darker than underlying hori cns because of the organic =atter concentration. Leachable, =oveable ions (iron, alu=inu=) and particulate matter (clay, some organic =aterial) are moved downward in the profile by percolating rainwater and groundwater. Material translocated frc: the A hori en accu =ulates in the 3. The 3 horizon beco=es enriched in silicate clay, iron, aluminu=, or humus, alone er in ec=bination. Quart cr other resistant minerals are concentrated in the A horizon with the loss of the clay, iron, or aluminum. The B horizon, because it receives material translocated downward from the A horizon, does not develop chronologically before the A. Develop =ent of the 2 horizons is conte =poraneous. 1 i 16

STATION NO. a + ss s +1s o +1s s + 14 o + 12 o tio c +ss o +6s o esa o + s2 o t ea e g a g a g i i e g a g e i e g e a g FAULT CONTINUED HIGHER INTO n'5jgg,tt SOIL PROFILE. N - n.o u.s -=== =- k1t'5 o.o ot*Eo /_ '- eo t i 1100E Rd-< tn susf5CE ' I f 50Lbli t lIA'~03 - -.o -t.o AII~ '.. 'l. -2.o f' ~ '. Illibt .-I ,g - Il, - 2. o , e ' ,g spi 'j.q: ~ 6u2I t _M-hI!8 3' ~ \\ CI-6007 ' C1-6006 ' - ~~~\\ ,.InEAs 2 {. ), b $_4,, H As-.81 ( _,,a x s _.a .._..- w _ m y a U-s.o IIIl81 p{' (Yl 'g-If B22 1 C E CI-E008 - 1 's - -s'o E i '~ 1 2 ~~~ -s.o " 'g / ! - - e.o l -J.o ge i, g gl%, 3 - - 1. 0 stort uAsa 2I O y /ll 1 .). i -s.o f 2, // -- - s.o s.a vtaticAL ExAscEsailow _e.s --e.o g Figure 9. heinterpreted log of. trench B-1 ( fig. A-8, reference 6), modified TRENoH B-1

==""""""""-1"""--"-

O ' 113.0.41d30 9 9 =. ,= 9 9 = r. s a e. a., e 5se 35 .Y = a 1;; c-zw y <a 'n 2_ =- e b 1 ~~ w 7

\\.\\.. (...,...... j c\\ _n.i. -\\ i.

i..., ; \\, 6r ;.. ,i s.s y ,,-= 1. 4 3-. .. qt\\ i - p-3 c s/ \\.. i. a

/ biii W_.

N i \\, \\, \\. \\ \\ \\, \\. v_ .=. e_ t .\\

i

\\ 1 i .m .a. = = i \\\\ .i i i \\ \\.\\ v c.- v 1, c;! i) i., ( z Z Z., g ( 1o. \\ a , i e i \\ti,g. d;i,i i iy t ~1 i. T

Z W

-n N i 4 2 pi. b. i t i i o-m i O

n 2

\\.a\\ 7.. n,,,, ,t w a ', /, i __ 1 9 .._ 1 : i, 1. ~,q. _v c t ,, s, A, \\,., s.,.i. 1, 4, m.s i,i ~ i n 1,. ,, \\.,.- y-m to ,\\ .. =,,,\\ ;~ ', './s\\ a u.J N .i ' -./ \\, w.=, ,. n e m u, ,- e ,.a s. co \\ g\\, :'o',N.\\e \\, \\,, i m N_. ,3, 3 i-e C'_' am O u. i'. ; ia 1 2-W 'd Z 2 i U? u. / '"\\ .,,\\ 'm O-c'~'- O ~ .\\ Z = T.'~i.=. \\,/..: /., . U. a- \\ \\ :. W 9,r '.\\ A\\ ;; v r-m '\\ Z Z n s'i G. 4 Q-J \\ ; a-C .pq \\ ~,, \\ a ye 5 W -] cg D .gg,,l- W Z O O, a \\,.(. c..A.- 5 'r - r i2 1 r .t a n

=

w, . r* m w <~ r O \\ :W j T.\\.a 5 n' x i-- W

w. u Z

r,n \\\\ a. f- .m c= e ;i \\ i, y# lEs d'- s' ~ \\ 6: s W i-_ c< a ~s W 3 "(4.Ny l._.-' \\ I W t-ai .I l i- - =5 \\ Nsj I i W I sa Q 0 4 \\ .1.1 w ,c Q 1 tc w a i o uo -I l.I,. C < zW ~,

i...

d

u___n, o007 3 C 45

215 4600*500 Ae-al O.6 5 -1.15
Bt 2.028 GX-60C6 4310*300 2440*l60 SI 1.15 -l.4 5 GX-60ll 216 0 *19 5 1475*2IO GX-6008 4240*195 419 5 *19 5 GX-6013 12408130 218 0 *19 5 H B2ltb 2.8-3.1 92 f.4 5 -1.7 C 922!!b 3.1-3.5 232tb I.7 - 2.3 H B222tb 3.55.3*
293tb
2. 3 - 2.3 2 Cl 2.9-3.3 2 C2

3. 3 - 4.1 2C3 4.1 - 5.0 +
Figare 11. Radiocarbon dates of modern soils in trenches 3-1 and 3-2, arranged by horizon and locality. Ages from Figare 7. I 20
climate and topographic conditions. There is no reason to believe that this soil achieved maximum develeptent before 8,000 3.?. It is still evolving. Whatever the actual time of initiation of soil genesis, a =cdern soil with recesnizable soil horizons new e*ists. Faulting occurred after the =odern 0011 achieved its present degree of maturity. There is no indication that the soil development has changed since the last episode of fault =cve=ent. Locally the A2 or Ae hori:en is separated from the A1 horizen by a buried soil that has been thrust between the two. We believe that this faulting cecurred since 2,000-4,000 B.?., and that there has been insufficient
'-a
-"a aurface soil to change its profile development to correct the internal ; rofile disruption caused by faulting. If this faulting had occurred 8 ^- or 10,000-15,000 years ago, there should have been sufficient time for a new soil profile to develop across the faulted soil. According to ESA the 3+ ft deep surficial soil was ferred in only 5,000 to 9,000 years. By their criteria there would have been more than enough ti=e to create a post-fault soil profile, as fully developed as that new seen today. RECURRENCE CF FAULTING Recurrent movecent on faults B-1/B-3, B-2, and H at the GETR site has offset successively older buried soils progressively greater amounts (6, t Appendix B). The offset of the youngest buried soil (believed to have formed during the last interglacial 70,000-130,000 years ago) is at least twice that of the albic horizon of the modern soil and the stoneline at its base (fig. 12). The underlying Livermore Gravels are offset an even greater amount. Figure 13 schematically portrays the progression of geologic events during the last 130,000 years that are represented at tranch B-2 (fig. 6). An unknown number of slip events occurred on fault B-2 before the deposition of 21 l i l
VERONA FAULT MOVEMENT CUMULATIVE OFFSET APPARENT DIP-SLIP SEPARATION AGE OF DISPLACEMENT UNIT (ft) Main Fault B-2 _H_. Total 200 (Prehistoric) to Stoneline/ B-1 T-l 6.5 (?)- <4000 years albic horizon 2 5 3 1.5(?) 9.5 (?) 70,000-130,000 yeers Youngest B-1 B-3 18 (?)- buried soil 8 -10 1 0 -11 6 4(?) 21 (?) 300,000-5,000,000 Livermore 8-1 years Gravels >40 >80 >29 >l49 Fieure 12. Amount and age of movement observed en faults in trenches B-1, B-2, B-3, and H. Tabulated or seasured in references 2, 6, and 9. 22 l
the alluvium /cciluvium in which the red-colored buried coil ferred 70,000-130,000 years ago: the underlying Liver:cre Gravels at trench 3-2 are offset at lea t 50 ft. During the last 70,000 and 130,000 years there were at least 2 faulting events. The buried soil is effcet 6 ft in trench 3-2, twice the 3-ft offset of the albic horizon of the redern soil and the steneline at its base. However, the buried soil en :ne upper plate is substantially thinner than its continuation on the icwer plate. Erosien has beveled the upper plate (Fig.13), reducing the apparent offset of the buried soil to 6 ft. There cust have been = ore than 6 ft of =ovement en fault B-2' since 70,C00-130,000 B.P. If the most recent 3-ft effset is char 20teri: tic cf the accunt of =cve=ent that occurrec en fault 3-2 during pact faulting events, at least 3 episodes of faulting during the last 70,000-130,000 years would be required to account for the c+ ft offset of the buried soil. The 3-ft offset of the albic horizon /steneline of the modern scil may also represent =cre than 1 fault movement. The offset of the albic hori:cn and that of the stoneline were not measured separately (6, Appendix 3). The two are of different ages (the albic horisen for:ed after the steneline); the stoneline may be offset somewhat more than the albic horizon. At trench B-1 (fig. 5) at least 2, and perhaps 4 er 5 fault cove =ents have occurred during the last 70,000-130,000 years. The base of the modern soil is offset only 2 ft. However, the underlying buried soil (believed to date from the last interglacial, 70,000-130,000 B.P.) is offset 8-10 ft. If 2-ft offsets occurred during past faulting events., then there were 4 or 5 episodes of =ovement on B-1 since 70,000-130,000 3.P. Si=ilarly, the albic hori:en/stoneline of the modern soil at trench H is reported (9) to be offset.- 1.5 ft(?). The 70,000-130,000-year-old buried soil at H is offset 4 ft(?). There must have been at least 2 fault move =ents at trench H in the last 70,000-130,000 years. 23
I BEFORE 130,000 B.P. 2 BEFORE 130,000 B.P. i FAULT IN LIVERMORE GRAVELS. MOVEMENT ON FAULT CARRIES LIVERMORE GRAVELS IN UPPER PLATE WESTWARD ACROSS FOOT-WALL. N:;; hC..x..::.';;;" ::..Nt. :~. :s..:... ' .:;.. s's. l.;; : .&n ...;:.. - n'.:... I s ... x..,s
x....
s.... Q. N.":.'.N,.. s.x :* ::.f:.N ;?. ~ x h.' s s ....x ..s ,'s . e.. s ...x N 1: i ,. : x.. %:... :.:;s.' x I .x d s ss. .s x s; ... y ; ~... i ..,x . c., '~...s ">,s l 3 BEFORE 130,000 B.P. i POST-FAULTING EROSION BACKWASTES TOE OF ?PER PLATE, BEVELING ITS LEADING EDGE. COLLUVIAL RUBBLE ACCUMULATES AT FOOT OF SCARP. t ,c ..s .s l .:,. \\.. s" 3.. s::. gg*!,3.;,. : C.'J'.:,9.'[".~. ~..,.' :: s'.*,,x Figure 13 Pictorial chronology or geologic events represented in trench 3-2 ( fig. 6). l 1 f 24
4 BETWEEN 70,000 AND 150,000 B.P. ? BURIAL OF FAULT SCARP WITH ALLUVI-UM AND COLLUVlUM. i \\ ~" ~ c x'S::'i;[#d!);;N:- 0 CC 0 0 C 0 , 5 0 0 g Qg\\::gh
= ;;%
xx 0 O O g 0 ,G g o 0 \\ \\ 0 0 0 g 9 C .O 6 \\ oO \\ 0,w \\ 9 0, o 3 Fipre 13, Centinued. 1 25
P i, 5 70,000 - 30,000 B.P. DEVELOPMENT OF REDDISH -C0LORED SOIL ( NOW BURIED ) IN SURFlCIAL COLLIJV!UM AND ALLUV!UM A HOR ZON ,/ e avR. Oh tin i z. . - -. - c. r:,m e.i r=.3 (~
'05 Y".
? ~~ k-4 %%'~U2 - -ammoim.au y ? ' v. 'f [ .*+1; awed. M i k .sp; .b. E O q g \\. 0'0' O C Q -3,; -f ?. '* / ,0 3 g
g 0
0', 3 2.shk .,- 4/4}. y # 's 3gn 3 s 's o a oO 3, senwn..- o ~0 O O 'O O ,o f 7M;s.eus a, y a 3 3 O 3 3o o 0 0 O s g 'N o*' \\' o' o, o o,,, 2 a,o. 'x's;N 'c. 'o 'NN 4 o o .c s 3 \\ 'S 0 \\\\
,o 3 w 's 0
s s' s a 2 o,- N o o. 6, \\ 's ', o, a => 'x ,,,o ,o, s oo l Fip re 13, Continued. I 1 si l
6 BETWEEN 70,000 -130,000 AND '7,000 - 20,000 B.P. MOVEMENT ON FAULT DISPLACES OVERLYING COLLUVIUM /ALLUVlUM Ah D ITS REDDISH COLORED SOIL. l' jrii&$5Y.1Tir. dE*!" ,n ,;, oy
obN4 M'M '
g' a y No,' o N-o f'
,o 2
o, o s 'Y,, ::;.,' " ; q':;:;;. L
o o,
s U* \\ ' o[o, N x ;x ,= ;;, .. s 'x ' ' ' ?o , l, s Figur'e 13. Continued. .' 7
7 BETWEEN 70,000 AND 17,000- 20,000 B.P. PERIOD OF LANDSCAPE INSTABILITY AND EROSION (WETTER AND COLDER WISCONSIN GLACIATION). FAULT SCARP IS BACKWASTED. SOIL ON UPPER PLATE, BECAUSE OF ITS HIGH-STANDING TOPOGRAPHIC POSI-
TION, IS TRUNCATED AND BEVELED.
RED SOIL PROFILE ON UPPER IS SUBSEQUENTLY MUCH THINNER THAN ON LOWER. STONEY LAG ACCUMULATES ON StJRFACE OF TRUN - a CATED RED SOIL. ~ q- ~ r c,, .,c, t 6~ ~ )df, _g$1.... xt::::~e.:%i:6?ss; ~ : e x 9 N sx; ~, e: : p y :,; x xx .N ,,,o e,N a e: o o, $o Ns ' o o u o ~. ~ ~ s. ~::
l ? l l l 8 AFTER .7,000 TO 20,000 B.P. END OF WlSCONSIN-AGE LANDSCAPE INSTAB LITY. BUR' AL OF RED-COLORED SOIL WITH COLLUVlUM AND ALLUVlUM. _/- 'ib': ,=!:'*::f}' I'~~ ,2 0, o O, o O, ,0 O 0 O S 0 0 g o *o h N
o, o
' o, N ' o,, o, s. Oo ~ ' Figure 13, continued. j 2 '1 i
9' AFTER 17,000 TO 20,000 B.P. DEVELOPMENT OF MODERN SOIL PROFILE IN SURFICIAL COLLUVlAL / ALLUVIAL MAbTLE. PROMih ENT ASEEN-COLORED Ae -OR ZON DEVELOPS. A HORIZOh l Ae HORIZON l B HORIZON M ' o,'.N, . 7yg,.. 3' o
0 3
o 1$(
r -
.a o o "h',.. O 3 0* o on O~s \\ h::}';.:.,'::.';,C N, '
. ;N s
/ N 's .. :. x s,..,s
1-BURIED PALEOSOL
's~- a Figure 13, continued. f 1 m
p j 10 AFTER '7,000 - 20,000 B.P. i l OFFSET OF SURFICIAL SOIL BY FAULT. l Ae 'ORIZON ATOP LOWER PLATE OVER-R.DDEX BY NOW-BURIED REMNANT OF l RED SOIL 'N UPPER PLATE. e i nivlrme n Y2" llA, "' ?
b l
f T****iTF ^ m h g [ 0 0 0
.n,.
y ::.". Ni 0 0 '#'l=;:'N:. ~ 3 Oo O O' O t O O O r 0 O O'% NO O 0 \\- 0 g h):.h'o if! 0 'N . ;,7*,
N a.
o Figure 13, continued. 31
11 AFTER 17,000-20,000
9 LOCAL MODIFICATION OF FAULT SCARP.
PARTIAL TRUNCATION OF UPPER PLATE SOIL PROFILE. SHALLOW BURIAL OF SOIL ATOP LOWER PLATE WITH COLLUVIUM. n _,, x,a rn u b = M @ h S M 5'f i$i'lii3 e"~ yy m***' 4 s 0 0 O l b\\ 3 O 0 O O' O o 0 s O' O Oo \\\\ ,0 0 s O g g 0 0 O 0 O o' g O 0 0 O o O O O O O O O O o g gN c:% O'- O O O 4 'N \\ O U o' \\ b O \\ \\ O g O Oo O O g \\ o0 w 0 O u 1 O N .O a 3 ~ Fiture 13, continued. l e
29 9) .G.-* u-An average slip rate can be estimated fer the fault at the GETR site by graphing the cu:ulative a;;3 rent dip-slip separation in the thrust fault zone against the age of displace:en: L' fig. 14). An average slip rate of 0.0004 ft/yr appears to best fit the data. ORIGIN OF B E FAULT SUEFACE3 The consultants cenclude (2, 6, 9) that the faults cbserved in the trenenes are snear surfaces at the ' case of a large landslide cc plex that ha: cue:ecuently been scstly rer:ved by ar0:i:n. Their evidence fer landsliding is su==arized en Figure 15. Crescent-shaced Architheater. Figure 16 is derived fec: Figure 4 of refe nee 2. The dached : lack line: ::p the cre :: f rilgt:. None cf these* crescent-shaped ridges is associated with large-scale land:liding according to the i l censultants (2, fig. 4) and Nil:en (10), une made a regional analysis of landslide features. The centinuity of bedding across some of the crescent-shaped ridges (2, fig. 4) shows the lack of large-scale landslide dislocation and indicates that the crescent shape cust have an origin unrelated to landsliding. The crescent-shaped feature inferred by the consultants to be the headwall scarp of a large landslide complex northeast of GETR was trenched in three places--no evidence for large-scale landsliding was found. Disturbed Bedding. The consultants indicate (2, p. IV-32) that beds within the landslide complex have a wider variation in attitude, due to rotation, than areas outs!':e the landslide. However, their geologic map (2, fig. 4) indicates that the reverse is true; that is, bedding attitudes outside the 33
(?t) Livermore Gravels z 150- = o_ l<- g* C O I 0 0 w o m 100 G. D 0 D &s s 6 1 e
z/
50-l- Z W T . Youngest buried soil Albic horizon /stoneline 0,. e< b IdO 20 30 4UO x 103 YRS Figure 14 Average slip rate en faults at the GETR site. Fault age / offset data from Figure 12. 1 l 1 34
Figure 15. Evaluatien of evidence for postulated large-scale landsliding in the GIT? area. Racerted Cbserved 1. Crescent-shaped amphitheater 1. Many crescent-shaped ridges in area--nene apparently related to landsliding 2. Bedding attitudes =cre dis-2. Reverse is true turbed in landslide area than in areas outside land-slide 3 Landslides are rotational 3 Dips within the postulated slump blocks. Attitudes slu=p block =cre gentle have wide variation due to than those outside--blocks rotation. Dips generally cannot be rotated by land-steeper sliding 4 Faults in trenches F & G 4 Faults in trenches F & G indicate head-scarp of deep-are at wrong angle for deep-seated slu=p block seated slump block and are related to shallow sliding l cr tectonic move ent 5. Berehole data indicate shear 5. Boreholes indicate shear surfaces in T-1 becc=e shallower surfaces in T-1 get in a northeast directien-- deeper in northeast probable landslide crigin direction--probable thrust fault origin 6. Fault in B-2 curves upward 6. Fault in 3-2 steepens to connect to headwall scarp downward 7. Headwall scarp continuous 7. No continuity of headwall scarp area can be demonstrated 8. No repeated movement ob-served en faults in headwall scarp area. Thrusts at base of hill have history of repeated movement 9. No evidence for sediment accu =ulation en down-dropped block 10. Landsliding does not explain anomalous geologic relations and thinning of section 35 ,w
F r- \\s\\g i 11 h / I i / I ~1 r ~j t %s% -s s N s g-3 1 I N \\ / / s\\ a 1 s n
y\\\\e us
\\ k k \\g ~s s k 4 % no # r f.. ;'.~. > e.+ } 7 GETRU C,. : ~' i ' ' y / w .t.- / aus % ~:% s ~ / O 1 2 Mitt 3 e i 1 -}. soon pEtt 0 I f L Plan of crescent-shaped rid 6es near the GETR. Dashed lines are Figure 16. ridge crests derived frem a topographic map (2, fig. 4). The. postulated landslide complex near GETR is from the consultant's map (2, fig. 4). 36
= landslide are more diverse than those inside. Figure 17, derived from their cap, shows the wide variation within pairs of closely spaced strike symbols in areas =apped as bedreck outside the landslide cc= plex. About one-third of the exa:ples have a 90c difference, the maxi =um possible. Within the postulated landslide cc plex, there is considerable disagreement abcut the directicn of bedding. Figure 18 is from the consultants' geologic map (2, fig. 7). During a field conference en April 12, 1978, the conciltants indicated that the attitude shown at locality 1 is not in the Liver:0re Gravels (CTign) as originally plotted, but instead is in young alluviu: and is unrelated to landsliding or tectonism. At localities 2 and 3, we agree with the consultants that the Liver ore Gravels strike about i 0 N.70 -80 W. At locality 4, the beds are severely contorted and several attitudes are present. We do not agree that the attitude shown on the map is representative. At localities 5, 6, and 7, the consultants were not able to relocate the beds frem which the attitudes were measured. In only 2 out of 7 observations do we agree with the reported attitudes, and both of these are parallel to the regional strike of the Liver: ore Gravels. Similar difficulties were encountered in evaluating the bedding attitudes i ~ provided in the consultant's trench legs (6). Some of the attitudes may have been recorded incorrectly; for example, in trench G-1 (fig.19) a 90-degree shift in strike from N.55 E. to N.55 W. in a well-bedded sequence in a short distance is unlikely. Some of the anc=alous attitudes are on features that do not seem to be bedding (figs. 20), whereas no attitudes are provided in parts of the section that are distinctly bedded (fig. 21). Nevertheless, all of the I bedding attitudes reported by the consultants for trenches F and G within the postulated landslide complex are shown on Figure 22 and 23 Taken at face value, the attitudes shown by ESA do suggest considerable variation within the postulated landslide complex. 37
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00 50 C =,:' 65 E 50 .; : 2 ( I 'I I g 40 00 70 l 60 h J s 00 j t i 00 y I a ,8 2, u n t s o , a o,oo ri t i n w Figure 17. Differences in strike of bedding near the GETR. The numbers on the figure refer to the angular difference withia pairs of closely spaced strike symbols on the consultant's geologic map (2, flg. 4). The pairs of strike symbols used are from the same geologic unit and are not from oreas mapped by the consultants as landslide or near fold axes. The large variation in strike indicates considerable disruption of bedding outside of the postulatea landslide complex.
9 r it, V. .I s t i anfr st i y.s. ./ .. e4; (~Na'7./.;/ ( J, ( ' ,1 w e . ! p, j ' r- \\ g',. N / y l *7.1 t s ~. L's '\\ .,,M .%Q i 1 %~. .ss., 1 ',.., o -s - ', ~ -l'. $,.$.. ',N \\ l , n..;,, ".- '., ',/, , t-c.. w ',.~. t 9- . ~. ,s; a r x ~-' \\
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43 = ,%3 _.e + V,* 7 2k f s s e s a. [ s n 'swet.e e rs, - caerti 'e ?'Lf f Casitj yg are per JawP t er.' te sevpfte f f.0, '.....,s.,t,,, ......,nai., i 1 ,e,c,,,.,,,,,,,,, ~ ~ " 's o n -+. 9, * .........u. ti i -<c=>u. z o. .e......,,,. irench G-1 Figure 19. Anc=alcus attitudes in trench G-1. Trench icg is part of Figure 0 E-12, reference 6. The change in strike from N.55 E. to N.55 W. in a distance of 20 ft is unlikely. I 8 J i f I l I l i 40 i i
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r. - l.:, re ference 6.
The ti.00 -65 E. and !!.85 -90 U. strikes do not .'l.7:0'7. .:.u.,ae < s clearly on bedding 4i appear to be cn %ddirr.
' $ a
nd it 's nearly parall 31 to the recicnal strike.
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w 4 SOURCES OF CATA 1) EARTH SCIEtlCES ASSOC:ATES TRE!!CH LOGS (5, fics. E-s to E-11) 9 STRIKES MEASURED -1 T10T USED SECAUSE DIP 5' OR LESS 4 8 1 5 il53'W TO E-W 2 l110*E T0 7416'W 1 ti 40'N l
2) MEASURED BY USGS 7 STRIKES MEASURED
- l_ tiOT USED BECAUSE DIP 5' OR LESS 5 fl75'TO tis 5'W ) 1 Figure 22. Ecse diagram shewing different interpretations of bedding strike in trench F. The solid lines are the strike of bedding reported by Earth Sciences Associates and the dashed lines are strike directions ceasured by the U.S. Geological Survey. l l. t 43 i . E-, 3 m..
P% N / N N / N N / N I N i N I N.. N- \\/L----- _,__~5 SOURCES OF CATA
1) EARTH SCIENCES ASSOCIATES TRE!;CH LOSS (5, FIGS. E-12 to E-14) 38 STRIKES MEASURED
-15 i0T USED SECAUSE DIP 5' OR LESS 23 10 il60* - NS5'N 5 1140' - !!55'W 6 il55 ' - i t.1' E 2 N7' l'.i' W
2) t1EASURED BY USGS 22 STRIKES MEASURED
-2 i;0T'USED BECAUSE DIP 5' OR LESS 20 20 1170*W TO E-W i l l i l Ficare 23 Rose Diagra::: showing different interpretations of beddinc strike i in trench G. The solid lines are the strike of bedding reported by Earth Sciences Associates and the dashed lines are strike i directions :easured by the U.S. Geological Surrey. 44
In late 1978 bedding attitudes in the trenches were measured by E. E. Brabb and plotted en a tcpographic base (fig. 24). A co=parisen of Figures 22, 23, and 24 indicates a censiderable differenes of cpinien about the direction of bedding. We be'ieve that the bedding within the so-called C landside ec= plex strikes reasenably consistently frc: N.70 W. to EW., except for a few small areas where the bedding has been disturbed by small, shallow landslides, er near the 7erona thrust fault where bedding has been disturbed by the faulting. For a statisticaly valid ec=parison, the bedding should have been measured in areas of comparable geology and relief, in trenches of..aal length inside and cutside the postulated landslide. Such cata are not available, but the attitudes that were measured indicate that the bedding outside of the postulated landslide is just as disrupted, if not core so, than the bedding inside the landslide. Pectulated Potational Slumo Blocks Figure 25 wac used by the consultants (9) to illustrate the rotational character of the postulatec landslide ec= plex. We have superimposed en this diagram the bedding dip infor=ation prcvided in the consultants' trench legs (6). The dip of the bedrock at the northeast end of the diagram, outside of j the postulated landslide, is not well e.stablished. The consultants' geologic map (6, fig.1) indicates a dip of 2'O in bedrock near the northeast end of the G trenches, and dips frem 180 to 35 on the opposite side of the ridge, about 3,000 ft northwest of the G trenches. The dips recorded by the consultants (6) in the G trenches are mostly about 15, but these dips may i have been flattened somewhat by surricial creep on a steep slope. A reasonable esth te of the bedreek dip outside the postulated landslide 0 complex is 20 to 240 45
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In bicek I cn the concultants' diagram (fig. 25), 16 of the 22 dips are 160 cr les:. If thi 510:3 h:d rotated d:wnward in the manner depicted by the censultant:, the prevailins dip :heuld be Oteeper, r.ct icwer, than the dip in the undisturbed bedrock. Althcuch the dios in 01cck 1, like those in the bedrock, eny have been affected by :urricial creep, they should not have been affected as Incn because the slepas are generally more Eent1=. In block 2 and in portions of bicek 3, many of the dips in the censultants' trench legs (6, figs. E-12, E-13, and E-14) are nearly 0 hori ental. Of the 97 dips in block 3, 7" are 15 or less. Again, the dips should be predominantly steeper than these in bedrock if the bic0ks had rotate: in the canner envisioned; instead, they are : re gentle. In su==ary, the dip of the bedding exposed in the G trenches indicates that the area northeast of the GETR did not rotate as several slump blocks. Oririn of Faults in ? and 0 Trenches In Figure 26, the dashed lines represent the sheared boundaries of the slu=p blocks inferred by the censultants. The shear that bounds the northeast part of block 1 is considered by the consultants (2, figs. 4 and 7) as tne continuous headwall shear of the postulated landslide ec= plex, but the shear was not found in trenches D and F. In trench G, the shear was so small it could not even be traced from one side of the trench to the other. Moreover, 0 i the strike of the shear in trench G should be about N.70 W. to conform with 0 the trace of the shear shown on the map; instead, it is N.10 g, The shear between blocks 1 and 2 is conjectural inasmuch as the trenches do not extend across that area and no other evidence is provided for the existence of that thear. i 47 t t 4.
i t DIP OF BEDDING ~22 total dips in block 1 ~ Total 20 dips in block 2 16 dips cre 16*or less including 2 horizontal /- 15 are 7'or less flone steeper than 24* 4 are 10*to 15* 1 is 15' I Trench G,- 9 Trench G-1 r i Southwest f flortheast f-f ~ ~ T-3 / at0CK 1 S '~~lLOCK3 / / BLOCK 2 'N_jooo ; igog_ GETR ,/' [ x f f// ~ [ ' ~ ~ ~.___._, / ~ ~ ~ Dip in bedrock w \\ 24'on geologic map ~0 o-SCALE -Total 97 dips in block 3 18* 35' 3000 f t flW of 0 1000 22 are 5*or less Ltrench. flostly 15' in trench feet 49 are 6*to 15* 14 are 16-20* 12 are 21-40' Figure 25. Dip of bedding in the hillside area northeast of the GETR. The basic diagram, including subdivision of the area into slump blocks and depiction of selected bedding dips as short line segments, is by Earth Sciences Associates (9). We have numbered the postulated slump blocks for ease of identification and have added to the diagram all of the Earth Sciences Associates data on bedding dips from their trench logs (6) and their geologic map (6, fig.1). The dips are generally flatter in blocks 1, 2, and 3 compared to those in bedrock, suggesting that the blocks did not rotate downward in the manner postulated.
SHEAR SURFACES These faults strike fl30*to f140E, parallel to line of section. They should be perpendicular to the line of section if they are related to pull-away scarp. They Conjectural - not are parallel to shallow landslide scarps. exposed in trench Trench G,-9 Trench G-1 r V ~f f-- fl Southwest ~TEtocK 2/ "' /kortheast ~ See T-1 diagram, fig'. 3 % /
7-N
~ ' _ _ BLOCK 3 1000-e , p ,,,,,/. Og - - -- mu y p-g ' ' ~ ~ _ - _ _ _. __'/ l T\\ BLOCK 4 This fault could not uj ~~ I traced from one side us SCAtE d W Wnch to um -o O' This fault steepens in trench B-2 o gooo other. Consultant says from 18*to 23*in upper part to 23* 2 to 3 ft movement. in lower nart of trench. There is ctrike fl10W, 45* evide'nce that it flattens in the no manner depicted on this diagram. Figure 26. The basic diagram is by Earth Sciences Associates (9). We have numbered the postulated slump blocks for ease of identification, and have annotated the postulated shear surfaces from data in reference 6. In our opinion, the shear surface directions are not consistent with the postulated slump block origin.
Several supplemental trenches were dug in the vicinity of the shears between blocks 2 and 3 (6, fig. E-13). These shears are called headwall-scarp surfaces by the censultants; the strike direction of the shears, as shown on 0 Figure 27, is about N.40 E. Figure 1 shows the directicn of last move =ent on the shear surfaces at the base of the hill, bounding block 4 in Figure 27. The predominant direction of movement is about S.45 'd. Thus, the strike direction of the postulated headwall-s:arp shears is nearly parallel to the direction of =ovement of the shears at the base of the hill instead of perpendicular to them as one =ight eypect if the shears were related to large-scale slumping. The geometry of the shear surfaces boundin;; block 4 in Figure 27 is critical. If the shear surfaces flatten at depth, as depicted by the consultants, then they could be associated with large-scale slu=p movements. Borings like those near T-1 would be helpful in determining the geometry of the shears near the GETE, but only the data from the trenches are available. In trench B-2 (6, fig. E-5), the shear surface steepens from 18 to 23 in the upper part of the trench to 280 in the lower part. In trench B-1, the shears bounding the northeast part of block 4 do flatten in one small area, but in the T-1 trench area, and along the same shear =apped by the consultants (6, fig. 1), we interpret the shear as steepening to 45 (fig. 3). In summary, none of the shears in the hillside area northeast of the GETR can be reasonably explained by large-scale slump movement in a southwesterly direction. All can be explained by small shallow landslides er by tectonic covement. Centinuity of Headwall Scare of Pestulated Landslide Comolex The line originally =apped by the consultants (2, fig. 7) as the headwall scarp of the postulated landslide complex was later crossed by three trenches; 50
DIRECTION OF HEADt.A!ALL SCARP SUR ACES s \\ l E- / lj?S v e. / v. 3 / c r'f/ n /,,,f
n 0
~ / /si s 12\\ k / > 1(O 3 q t ' Figure 27. Faults in the Oentral part of trench G. Figure and annotations unchanced free reference 9 The strike of these faults is centistent with novement of the landslide shown en the rap or with tectonic n0vetent but n0t with southwest.:vement of slu p bl0cks. 51
no evidence was found for any significant slu=p movement in those areas. Subsequently, the censultants (11, p. 98-99) changed the position of the headwall scarp to the fractures in trench G shown on Figure 27. These fractures are along an east-trending line that the consultants identify on their geologic map (2, fig. 7) as a landslide-slip surface. The fractures in 0 trench G, though, trend N.40 E., a direction inconsistent with the east-west trace. Moreover, no continuity of this shear from cne hill to the next has been demonstrated. Ticine of McVetents The consultants indicate (6, p. IV-3) that soils are not displaced by shears in the postulated headwall scarp area (fig. 28). Moreover, there is no l i evidence for multiple offsets on these shears, or for the deposition of materials on the downthrown blocks. In contrast, the shears in the vicinity of the GETR displace Holocene soils and have multiple offsets. Therefore, the shears near the GETR cannot be the same as the shears in the headwall scarp area because; the two sets have different =cve=ent histories. Anomaleus Geolegic Relations and Thinning of Sectien The consultants' geologic =ap (2, fig. 4), reproduced in part on Figure 29, shows the middle conglomerate me=ber of the Livermore Gravels (QTlgm, colored orange) as a continuous unit extending around ine west and south perimeter of the reactor site. The same map shows gravel-rich beds in the upper part of the Livemore Gravels (part of QTigu, colored purple) striking 0 0 N.50 W. and dipping about 30 NE. About 2 mi northeast of the GETR, these two units strike into each other at right angles. This structural anomaly has not been explained by the consultants; we believe the structural anomaly is explained by thrust faulting along the Verona fault. 52
TIMING OF FAULT MOVEMENT No liolocene oftset Ni muluple of fsets No dew;1 tion of nuterials on downthrown telo(L Holocene offsets Hultiple offsets Southwest Northeast / -1000 e 1000-f. GETR ~ e s %s ~ ~ e'-~ ~ ---- /e-y e f tu uj -- ~ ~ _ _ 0-SCALE -0 0 1000 feet Figure 28. Timing of movements on shear surfaces in the vicinity of the GETR. Figure from reference 9. We have added the annotations on age of the offsets. The shears near the GETR have movement histories different from those of the shears postulated in the northeast part of the section.
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In addition to this structural discordance, there is a drastic change in thickness of the section between the middle congiceerate = ember (colored orange) and the upper gravels (purple) from the area northwest of the GETR to the area northeast of the GETR, across California Highway 84, near La Costa tunnel. The consultants (4, p. 4-5) explain this difference in thickness by progressive eastward thinning of the section due to normal sedimentological processes. They constructed a series of cross sections (4, fig. 21) in the areas shown en Figure 30 to show this progressive thinning. The information in their cross sections, however, does not agree with the information on their geologic map (2, fig. 4). In section CC' (fig. 31), for exa=ple, the geologic =ap shows that the middle congiccerate has nearly horisontal apparent dips in the line of section instead of the steep dips shown. A preliminary construction using these data indicates that the thickness of the section between these units along section CC' is actually about 300 ft, not 700 ft. Similar corrections for DD' (fig. 32) and EE' (fig. 33) suggest a thickness of 400 ft, not 1,500 ft. On section FF' (fig. 34) the geographic and structural separation of the two units is so great that no reliable estimate of thickness is possible, but a thickness of 400 ft is reasonable from the data on the geolegic =ap. i l In section GG' (fig. 35) northwest of the GETR, Earth Sciences Associates (4, fig. 21) obtained a thickness of 3,300 ft for the section between the middle conglomerate and the upper gravel; we agree with this estimate. They did not provide a thickness for HH' section (fig. 36), probably because the upper gravels cannot be mapped reliably into this area, but the gravels shown on their geologic map probably are equivalent to the upper gravel, giving a thickness somewhere between 3,200 and 3,800 ft. 55
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Apparent dips nearly horizontal along g, C line of section South North 2000-Lo Costa Volley La Coslo Vollecilos Hdie 800 .s. w QTigt \\ ') N 4 / 9 l8" Tc N c1: 0-400N vi N ilorizontal scale - \\ M g vertical scale, in feet
c Figure 31. Different interpretations of the stratigraphic interval between the middle conglomerate member of the Livermore Gravels (QTlgm),
and gravel beds (stippled pattern) within the upper member of the Livermore Gravels (QTlgu) in section CC'. Section from reference 4, flg. 21; we added the heavy black line and the comment about the apparent dips. Earth Sciences Associates indicates that the thickness of strata between the middle conglomerate (QTlgm) and gravel beds within the upper member (QTigu) is about 700 ft; we believe the thickness is about 300 ft.
Apparait dips in this ar ea D ore neqrly horizontal along 9 line or section South Nor t h j 200 - vou.cieu / Atti tudes on saap 12-35* La co.ra vo'8'r nin. / / /- r'% -' C g ^ - ~ T 1000 7 . q [s ;'A., q q n -s 4 - 40 / s N N [N u h .1-5 m o_ g 4 N, , ougo oTige oTy$%,./,,3ngftX'g florizontal scale = rf vertical scale, in feet Figure 32. Different interpretations of the stratigraphic interval between the middle conglomerate of the Livermore Gravels (QTlgm) and gravel beds (stippled) within the upper member (QTlgu) in section DD'. Section from reference 4, fig. 21; we added the dashed black line and the annotations about the attitudes. Earth Sciences Associates indicates that the section between the middle conglomerate (QTlgm) and gravel beds within the upper member (QTlgu) is about 1,500 ft thick; we believe the section is about 400 ft thick. G
E' E NE SW Apparent dips nearly horizontal Attitudes on map 32-35*, u.ra.o.. votier vau.citas 666ils 2000 - ^ g apparent dip somewhat less m s000 - Ns'aty.' \\s;. 40;f.' -4C- & V - -- _,- c ~ M sgg h OTigi 4 O - oj[gh 30' o Igu T Horizontal scale j gg3o \\ \\ vertical scale, in feet ,/ ft yg L 4 O $g Figure 33 Different interpretations of the strat igraphic interval between the middle conglomerate of the Livermore Gravels (QTlgm) and . gravel beds (stippled) within the upper member (QTlhu) in secticn EE'. Section from reference 4, flg. 21; we added the dashed ohk lines and the annotations about, attitudes and apparent dips. Earth Sciences Associates (ESA) indicates that the section betwun the middle conglomerate member (QTlgm) and gravel beds withiri the upper member (QTlgu) is about 1,600 ft thick; we believe the section is about 400 ft thick. About 200 ft. z.hould be deducted from the ESA figure because they measured t.o the top of the Jowest gravel bed and we measured to t.he base of this unit, but t.he large discrepancy remains.
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l>ifferent interpretations of the stratigraphic intervat between the middle conglomerate of the Livermore Gravels (QTlgm), and gravel beds (stippled) in the upper member (QTigu) in sect. ion FF'. Section from reference 4, flg. 21; we added the. dashed black line anG '.he annotations. Much of the sect. ion is paralit? to the strike of bedding, so that t.he stratigraphic thickness earmot, be determined reliably. Earth Sciences Associat,es indicates that, the section bet. ween the middle conglomerate (QTigm) and gravel beds within the upper member (QTlgu) is about. I,650 ft; we believe a thickness of 400 ft, is more reasonable.
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l H H' -o-SW NE 2000} Vollecitos Hiliuont Vollecitos Riis Foley el %4,,, \\g 4 OTigu \\ 0-s %g\\ % N OTigm ~ C' llorizontal scale = eg, o @ OTigu g 4. vertical scale, in feet N d, ~ s. f T D 6til' Figure 36. Stratigraphic interval between the middle conglomerate of the Livermore Gravels (GTlgm) and gravels beds (dashed lines) in the upper member (QT1gu) in section 1111'. Section from reference 4, fig. 21; we added the dashed black lines from information on Earth Sciences Associates geologic map (6, fig. 1). The thickness of the section between the middle conglomerate (QTlgm) and gravels within the upper unit (QTlgu) is on the order of 3,200 to 3,800 ft. 9
Thus no progressive eactward thinning of the strata between the =iddle congiccerata and :ne u; par gravel has been e ::blished. These strata are about 3,300 ft thick northwest of the GETR, and about 400 ft thick east of California Highway 34 The abru : change in :nickness coupled with the 90 disecedance in strike indicates either an unccnformity or fault. No other evidence fcr n unconfer:::7 has been fcund; we celieve the missing section and angular discordance are best explained by faulting along the Verona thrust fault. To tect :ne nypothesis tnat the acrup; change in thickness of the upper 1 gra'.el and an;211r dicccrdance are related Oc he Verona thrust fault, trench A was cug :y Earth Sciences As cciates in :he vicinity of La Costa Tunnel (fig. 1). Trench A did reveal a major faul; cene (6, figs. E-1, E-2, and E-3). Earth Sciences Associates have interpreted this fault zone as part of the C Willian fault, eni:n trend: accut N.25 N. The faults in trench A, however, 0 C trend N.c5 W. to N.35 W., consistent with the trend of the Verona fault as it extends eactward fec: the GETE area to La Costa Tunnel (fig. 1). The abrupt change in thi:xness and angular discordance are easily explained by movement along the Verena thrust fault--they cannot be explained by movement on the Williams fault. The evidence available indicates that there is no large-scale slump-type landsliding in the hillside area northeast of the GETR. All of the evidence is co=patible.with a thrust fault origin for the shears observed in the trenches at the base of the hill (B-1, B-2, B-3, H, and T-1). 63
TECTCNIC FRAMEWCRK The Verona fault occurs within one of the most unusual tectonic settings in coastal California (fig. 37). The Verona fault lies between two active right-slip faults--the Calveras-Sunol and Greenville, and is connected at its southeast end to the Las Positas fault, a northeast-trending, left-slip fault which bounds the south side of Livermore Valley (fig. 38). The Calaveras-Sunol fault is a branch of the Calaveras-Paicines fault, which joins with the San Andreas fault south of Hollister. The Greenville is the easternmost seismically active right-slip fault in the central Coast Ranges of California. The Las Positas is 1 of 2 only known active left-lateral, strike-slip faults in the California Coast Ranges north of the Western Transverse Ranges. One of 3 active thrust faults in the San Francisco Bay area (the Monte Vista (13), and Evergreen (14), which flank San Jose), the Verona fault cuts the south limb of the Livermore syncline. The SE-trending syncline underlies Livermore Valley, ending southeast against the Las Positas fault. The Verona fault crops out at the foot of the hills behind the GETR, which are underlain by Pliocene-and Pleistocene-age Livermore Gravels dipping northeastward into the axis of the syncline. Folding of the Livermore syncline was apparently followed by movement along both the Las Positas and Verona faults. South of the Las Positas fault the Livermore Gravels dip gently northward and are little deformed. Thrust movement along the west-northwest-trending Verona fault appears to result frcm its nearly perpendicular orientation to the maxi =um stress axis. As the Pacific plate moves northwestward past North America, an essentially N-S compression is created along the plate boundary. The naximum stress axis of this right-lateral couple lies at an angle of about 30 to the strike of both i 64 l
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izo. h. A -s _e s. gi o e-. 0 c. 7 4* N p > 7 :m. g SAW A4,:pT4s . Mon *erey - SeqLeer m _fL -f) narzu w o m v T s 9 g c 7% S f' k f*. '2#o h h I 't,# / T 2. cm... m-Mor:*eavy ,.se + w-Figure 3'7. Map of principal recently active faults in the San Francisco Bay regicn, showing senes of surface rupture associates with historic earthquakes. Squares denote locally determined rates of geologic o ffset. Updated versien of Figure 1, reference 11. 63
12 2* 121' 45' i 37*45' g S l/ @G T-1 1 Dublin ? p ~ / I$.hm Livermore m \\ 9 M W c s(P!ecscnton ,#qb z-. VERONA \\ o -n Z. 9 y-E dv F 37'34' Figure 35. Tectonic frar.ewor'< af the Liver cre Valley, California. Arrows show crientation of taximur. compressive stress axis. l 66
the Calaveras-Gunol and the Greenville faults (the maxi =us stress axis of a 0 stress ellipsoid bisects the 60 angle between intersecting strike-slip failure planes of the stress ellipsoid). This right-lateral stress couple causes right-slip movement along the northwest-trending Greenville and Calaveras-Sunol faults, and left-lateral, strike-slip =ovement along the northeast-striking Las Positas fault, which lies at a 60 angle to the Greenville. Livermore Earthcuakes of 1980 An earthquake sequence which shock Livermore Valley in January 1980 confirmed our tectonic model of Livermore Valley, and revealed that faulting can cccur si=ultaneously en more than ene of the valley's faults (15). About 11 a.m. Pacific Standard Time en January 24, 1980, a =oderate earthquake (M 5.8) cccurred north of Liver = ore Valley about 7.5 mi southeast of Mount 3 Diablo (fig. 39) en the Greenville fault. Or January 26 at about 6:30 p.m. local time a second moderate earthquake (M 5 2) occurred on the Greenville 3 fault just north of Interstate 580, about 8.8 mi to' the south of the first earthquake. Although there were no large aftershocks identified on the Las Positas fault, field investigations af ter the two earthquakes revealed that surface rupture occurred alcng both the Greenville and the Las Positas as =apped by Herd (1). A 2.6-3.9 mi length of the Greenville fault north of Interstate 580 ruptured during the earthquake sequence. A =aximum right-lateral displacement of 1 in, and vertical offset of 2 in (includes gravity effects of unknown amount) was measured along the Greenville fault. A s=all (about 0.2 in) amount of left-lateral slip on the Las Positas fault zone fractured roads in at least 2 localities less than 0.7 mi apart. 67
i i 45' Screen shows [ = M/. C ab/o rupture on faults. DnM :5.8 3 Dcnville y- / M 'g', - %[ g spD oA \\ ?p%2 { )c # g.A M,= 5.2 .A s g,........ '..
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\\- ,%. ). VERCNA E,Z. o 5km s Figure 39 Map showing location of the January 1980 Livermore earthquakes and the accc=panying surface rupture en the Greenville and Las Positas faults. Earthquake epicenters from Benilla and others (15). Faults after Herd (1, 12). 63
The simultaneous surface rupture of the two intersecting strike-slip 1 faults with oppo:ing direction of move =ent was the first observed in North America. Simultaneous movement on left-and right-slip orthogonal faults had been seen previously in Japan during the Tango earthquake of 1927 and the Izu earthquake of 1930 (16). AGE OF LIVERMCRE GRAVELS The age of the Livermore Gravels is relevant to the age of possible faulting beneath the reacter vessel, but has not been well established. Shlemen (6, p. B-3) indicates that this unit is at least 350,000 years old, based en the ages of soils develcped on the gravels. Direct evidence is provided by vertebrates collected from the Livermore Gravels along Highway 84, about 1.9 =i northeast of the GETR (locality M-1442). According to C. A. Repenning, H. Wagner, and S. May of the U.S. Geological Survey (written co=munication, August 20, 1979), the fauna contains the following species: "Hvrolagus li=netus Gazin ?Hypolacus vetus (Kellogg) Percenathus of. P. =agnus Zakr:ewski Pliorec=ys parvus Zakreewski Horse, not identifiable The youngest record of Hypolagus vet :s is about 2.6 m.y. The known range of Hyeolagus linnetus is younger than 3.8 and older than 2.5 m.y., although Andre Sarna-Wojcicki's tuff dates along the road to Lake Del Valle by M-1431 would seem to extend the oldest known occurrence to 4.0 m.y. All species from this locality are known from the Hagerman fauna of Idaho (ca. 3.7 to 3.3 m.y., ' eville and others, AJS, 279/503-526). An age between 4.0 and 2.5 m.y. is indicated with the suggestion that it probably is close to the middle of this range. This is mid-Blancan =at=al age (Blancan II, III, or IV but most similar to Blancan III)." 69
Another relevant lccality, M-1135 along the banks of San Antonio Ee:ervoir, is about 1.9 mi scutheast of the GETR. Liver:cre Cravel: there c0ntain, according to Repenning, Wagner and May: "Ecuus (Delichchiccus) sp. This horse is known to have lived between 1.2 and 4.5 :.y. ago in North America." The youngest faunas collected from the Liver ore Gravels are frc= a locality (M-1441) alcng North Livermore Avenue, about 6 3 mi northeast of the GETR. The fauna contains, according to Repenning (written 00 unication, January 18, 1980): " Fish, not identified Turtle, not identified Snake, not identified Bird, not identified Paranyloden harlani (Owen)? Sylvilarus audubenii (Baird) 3rer0rnilus tcwnsendi Sachnan Themerys of. T. umbrinus (Richardsen) Dicedemys sp. Reithrodonte=ys aff. R. tecalotis (3aird) Neotera cf. N. albicula Hartley Needen readensis (Hibbard) Microtus californicus (Peaie) Proboscidean Seven species in the fauna are still living and the Dicode=vs certainly could be a living species. Soermochilus tewnsendi, however, is greatly out of place with respect to its modern range: Nevada, eactern Oregcn, southern Idaho, and western Utah. The same could be said of Neotoca albigula which was tentatively identified; this species new lives in the southernmost I=perial Valley of California, and in Arizona, New Mexico, western Texas, and Mexico. This modern look of the fauna would suggest a young age, except for Needen. The species Neoden readensis is the most time-significant element of the fauna. This microtine rodent is extinct, although a close 1 l 70 + l l l
I relative still lives in a small area east of Mexico City. Its dated temporal range in the United States is from 1.2 to 0.6 m.y. It appeared in this continent by ic=igratica from Asia, where the genus still lives from western Nepal eastward to northern Burma, S echuan and Hansu, essentially the south and east edge of the Tibetan Plateau. The youngest dated record of Neoden meadensis is in the Cudahy fauna of Kansas at the base of the 600,000 year old Tvpe "0" ash. Extinct species constitute 66 percent of the rodents known from the Cudahy fauna. Of the eight rodents from North Livermore Avenue fauna, only Needen meadensis is clearly extinct. The seven living species of the fauna are products of ende=ic evolution in North America; five of these belong to genera that are represented by extinct species in the Cudahy fauna. The next =icrotine rodent invasion of the United States, =arking the beginning of a younger faunal age, is currently dated at 450,000 years by correlation to oxygen isotope Stage 12. These invading microtines are presumed to be the cause for the extirpation of Neodon mesdensis from the United States for there is no record of this genus or species in these younger faunas except in Mexico. From these constraints, it is =y opinion that the North Livermore Avenue fauna is significantly younger than 600,000 years old but older than 450,000 years. The nature of the modern habitat of Soerrochilus tewnsendi, Neoteca albigula, and even Neodon itself strongly suggest hot and very dry sum =ers and the possibility of a correlation with oxygen isotope Stages 13 or 15, although Stage 15 is not very much younger than the Cudahy fauna. By E=iliani's (1978) composite Caribbean "cora", Stage 13 was about 475,000 to 530,000 years ago." 71
O 5 The 'traer age limit of tne Livar cre Gravels is restricted by the age of 1 111uvial terrace depcsits resting une:=fercably a:cve the gravels in Liver: re 7:11ty. 7:ur terrace unit: have been =apped (1). Fre: cne of the (Oca2' i rec:nd frc: / unge:t terr 20e f::ve the =0dern fleed alain) in Doolan Canyon, abcut 7.5 mi ncrth of tha GITR, the felicwing fessil was reported by Repenning,~4agner, and May (written ec==unication, August 20, 1979): "Mammuthus celusti 'yal::ner) Age: 1.3 :.y. cr younger." 430 ft farther south, the Univer:ity :: lalif rnia palecntologists collected material frc elay: Of :he : r::: C ant:. " (Localit7 7 4103) Mammut of. _M.. *-aricanur Pararyloden of. ?_. Mariani 310:n cr. _3_. anticuus ,cuus sp. The presence Of 31:en in their eclinti:n strenglf Ouggests i Rancholabrean II ca= al age that 2; pears, fr:: inf:rmation available to date, to be younger than 175,000 years old." '4e believe these terrace deposits are correlative with those directly beneath the GITR. i I Using the soil and isotope stage correlatiens developed by Shle=en and others (17), the oldest terrace deposit (Ocag) resting unconfor ably on the Livermore Gravels =ay be about 300,000-350,000 years old. Thus, both soil stratigraphy and the vertebrates indicate that the upper:ost part of the Liver: ore Gravels is older than 300,000 years and nuch younger than 600,000 years. The age of basal Liver ore Gravels is not as well established. The Liver:cre Gravels rest uncenfor: ably on the Oursan Sandstone of =iddle Miccene age in the Arrcyo del Valle area about 5 =i east of the GETR, according to 1 i Huey (18). In this sa e area, a tuff about 660 ft above the base of the -n to
Livermore Gravels has been dated by Sarna-Wojcicki (19) as 4.520.5 =.y. old. At locality M-1431, about 30 ft stratigraphically above the tuff, the following fossil was collected: "Hyeolacus limnetus Gazin Lower p3 and 3 other lower cheek teeth; upper cheek tooth and a few dentary fragments." At location M-1432, several hundred feet above the tuff, the following fossils were collected: "Hypolacus sp. cf.1[. furlenei Gazin Lcwer p3 slightly worn and 3 upper cheek teeth. An unidentifiable fragment of a horse lower cheek tooth was also found at this locality." According to C. A. Repenning (written c0==unication, April 25, 1979): "The record of these small species of Hvoolacus is weak; however, the genus is almost exclusively Pliccene and older. j[. limnetus was described from Blancan III deposits between 3.7 and 3.4 m.y.o. and 1[. furlenei from Blancan V deposits between 2.5 and 1.3 m.y.o. In the Snake River basin of Idaho, the two species have overlapping ranges in faunas that are as young as 2.5 m.y. and as old as 3.1 m.y. Earliest Pliocene forms (between 4.8 and 5.4 m.y.o.) seem related but separable from these younger species. There is virtually no record of related small species during the following one millien years that precedes the earliest record of H. li=netus. The suggested age therefore is between 2 and 4 m.y. but could be more than 4 m.y. based upcn current lack of records." In su==ary, paleontolegic and other information indicate that the Livermore Gravels are not younger than 300,000 years (Pleistocene) and not older than about 5 m.y. (Pliocene); their deposition spans a time ranging from 73
about 2.5 to less than 0.6 millien years ago. The beds closest to the GETR are probably 2.5 to 4.0 m.y. old, but given all the uncertainties in 4 j correlation, the wider age range (300,000-5,000,000 3.P.) for the formation as + a whole is a =cre conservative esti= ate. i ' Assuming that the alluvial deposits exposed in trench B-1 extend beneath 4 the GETR, the reactor rests on beds that are older.than 70,000 to 130,000 years and younger than 300,000 years. If the reactor rests directly on ~ Liverscre Gravels, it is en deposits that are older than 300,000 years and younger than 5 m.y. f i 4 i l 1 i i i 1 1 1 I h i I I l 74
References Cited 1. Herd, D. G.,1977, Geologic map of the Las Positas, Greenville, and Verona faults, Eastern Alameda County, California: 'J.S. Geological Survey Open-File Report 77-689, 1 sheet, scale 1:20,000; 25 p. text. 2. Earth Sciences Associates, February 1978, Geologic investigatien, General Electric Test Reactor site, Vallecitos, California: Palo Alto, California, varicusly paginated. 3 U.S. Nuclear Regulatcry Cc==issien,1977, In the matter of General i Electric Cc=pany (Vallecitos Nuclear Center - General Electric Test Reactor), Operating License No. TR-1, order to shcw cause: '4ashington, D. C., 9 p. 2 Earth Sciences Asccciates, April 1978, Geologic investigation, General 1 Electric Test Reactor site, Vallecitos, California, Addendu: 1: Palo Alto, California, 5 p. 5. Earth Sciences Associates, July 1978, Landslide stability, General Electric Test Reactor Site, Vallecitos, California: Palo Alto, California,16 p. 6. Earth Sciences Associates, February 1979, Geologic investigation, Phase II, General Electric Test Reactor Site, Vallecitos, California: Palo Alto, California, variously paginated. 7. Jahns, R. H., February 1979, Evaluatien of seismic hazard at the General Electric Test Reactor Site, California: 19 p. 8. Brabb, Earl, Herd, Darrel, and Devine, J. F., (September) 1979, General Electric Test Reactor, Vallecitos Nuclear Center, Vallecitos, California: U.S. Geological Survey Administrative Report, 17 p. t 75
9. Earth Sciences Associates, (Nove=ber 1979), Advisory Committee on Reactor Safeguards, Meeting of GETE Cubectrittee, November 14, 1979, Presentation by Earth Sciences Associates: Palo Alto, California, i unpaginated. 1G. Nilsen, T. H.,1973, preli=inary photointerpretation =ap of landslide and other surficial deposits of the Livermore and part of the Hayward 15 minute Cuadrangles, Alameda and Contra Costa Counties, California: U.S. Geolcgical Survey Map MF-519, 2 sheets, scale 1:62,500. 11. Nuclear Regulatory C ::ission, Advisory Cctsittee en Reactor Safeguards, 1979, In the matter of: Subec==ittee meeting on General Electric Test 3eacter (November it, 1979, Burlingame, California): Ace-Federal Reports, Inc., '4ashington, D. C., 331 p. 12. Herd, D. G.,1979, Neotectonic framework of central coastal California and its i=plications to micro:cnatien of the San Francisco Bay region, jn., Brabb, E. E., ed., Progress en seismic tonation in the San Francisco Bay regien: U.S. Geological Survey Circular 807, p. 3-12. 13 McLaughlin, R. J., 1974, The Sargent-Berrocal fault sene and its relation to the San Andreas fault system in the southern San Francisco Bay region and Santa Clara Valley, California: U.S. Geological Survey, Journal of Research, v. 2, no. 5, p. 593-598. 14 Dibblee, T. W.,1972, Preliminary geologic map of the San Jose East Quadrangle, Santa Clara County, California: U.S. Geological Survey Open-file Map, 1 sheet, scale 1:24,000.
15. Bonilla, M. G., Lienkae: peer, J.
J., and Tinsley, J. C.,1980, Surface faulting near Livermove, California associated with the January 1980 earthquakes: U.S. Geological Survey Open-file Report 80-523, 27 p. 76
16. Benilla, M. G., 1979, "i:t0ric surface f aulting--Map patterns, rela-icn e-... - - -. - ~,, 1 n. a...,.< -..,.,,.. -~<. s- . o s u,u...... 1n.,. .er. .-e.....-- Geol:gical Sur tey Cpen-file Report 79-1239, p. 36-65. 17. Shlenon, R. J., Wright, R. H., and 7ercsu'c. K. L., *980, Late Cuaternary nultiple buried paleosols, Vallecit:0 Valley, Ala: eda County, Ca,, s, 2 0,.../ .--.- a n. .,...w 4, .w c,,c3.,.a.s e.. - -, A,.... _, s .s Prograts, v. 12, no. 3, p. 152. 18. Huey, A. S., 1908, Geclegy of the Tesla Cuadrangle, California: California Divicion of !!ines 2ulletin 120, ~5 p. 19. Sarna-Wojcicki, A. M.,1976, Correlati:n of late Cen 20ic tuff; in the central Ceast Ranges cf Calif:r-ia cy eans of trace-and siner-ele:ent chemictry: U.S. Geological Survey Professicnal paper 972, 30 p. l l l gg de}}

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