ML16341C361

Affidavit Advising of Recent Investigations Indicating That Hosgri & San Simeon Zones Represent Continuous & Throughgoing Fault Sys.Chart Encl

ML16341C361
Person / Time
Site:	Diablo Canyon
Issue date:	02/28/1980
From:	Leslie R CALIFORNIA, UNIV. OF, SANTA CRUZ, CA
To:
Shared Package
ML16340A907	List: ML16340A906 ML16340A908 ML16340A909 ML16341C361 ML19323A544
References
NUDOCS 8004210329
Download: ML16341C361 (14)

Text

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In The Matter Of: )

GAS AND ELECTRIC COMPANY) )'ACIFIC

) Docket Nos. 50-275(OL)

(Diablo Canyon Nuclear Power ) 50-323(OL)

Plant Units 1 and 2) )

AFFIDAVIT OF ROBI B'RUCE LESLIE STATE OF CALIFORNIA )

) ss.

COUNTY OF SANTA CRUZ)

ROBIN B. LESLIE, bei'ng of legal age and duly sworn, deposes and says as follows:

1. I am a graduate student in Earth Sciences. (geology) at the University of California, Santa Cruz campus. I completed my B.S. degree from the: University of California, Santa Cruz in Earth Science:in June, 1978. I am currently completing work on a geophysical study of the central California coast between Cape San Martin and Pt. Estero as a portion of my masters, degree.'program.

I expect to receive my M.S. degree in June, 1980. Prior to college, I served for four years in the U.S. Navy where I reached the grade of E-5.

As part of my masters thesis I designed and con-ducted a seismic reflection data collecting cruise of the shallow nearshore areas between Cape San Martin and Pt. Estero.

I have interpreted this data in conjunction with pre-existing

/

reflection profiles obtained by the U.S.G.S. as well as data privately collected by the firms of. Bolt, Beranek, and Newman and Aquatronics. In addition, I am currently employed by the U.S. G.S. to interpret and report on this new data. Hence, I am very familiar with previous investigations of the geology of the central California coast, including the investigations of the relationship between the San Simeon and Hosgri fault zones.

I presented preliminary conclusions of my investigation to the American Geophysical Union at the Fall 1979 meeting which took place in December 1979 in San Francisco, California.

2. The purpose of this affidavit is to describe my investigation of the relationship between the San Simeon and Hosgri fault zones. My affidavit demonstrates, based on the recently acquired sei;smic reflection'ata, that the San Simeon and Hosgri fault zones represent a continuous and throughgoing fault system. Further, my affidavit demonstrates that the Hosgri

fault zone veers toward the San Simeon fault zone in the between Pt. Estero and San Simeon Bay. 'egion

3. The continuity between the San Simeon and Hosgri fault zones is of critical importance due to the numerous evolving models for the Neogene tectonic evolution of central California. These models incorporate right lateral offsets along the San Gregorio-Hosgri fault trend which range from less than 20 km as suggested by Hamilton and Willingham (1977) to as much as 115 km as proposed by Graham and Dickinson (1978) .

Hamilton and Willingham's model does not require a continuous San Simeon-Hosgri fault trend. However, the models, proposed by Hall (1975, 1978), Silver (1974), Graham and Dickinson (1978),

and Dickinson and Seely (1979), do require a continuous San Gregorio-Sur-San Simeon-Hosgri fault system.

4. The U. S. Geological Survey fault map of central California (Buchanon-Banks et. al, 1978) illustrates the offshore faults of coastal central California as well .as faults which have been mapped on land. In the shallow near-shore areas where the relationship between the San Simeon fault zone and its offshore extensions is in question, data were lacking. The purpose of my study was to collect high resolution seismic reflection data in these near shore areas in order to clarify the structural relationship between the San Simeon and Hosgri fault zones.

Highresolution seismic reflection profiles were obtained in the shallow near shore 'areas between Cape San Martin and Pt. Estero from the .University of California at Santa Cruz R/V Scammon during the April 1979 cruise. The track chart for my cruise is shown in Attachment A. The high resolution reflection profiles were obtained using a 500 joule mini-sparker system with either .5 or .25 second fire/sweep rate (Leslie, 1980) . The quality of the data varied with sea conditions, but in general is very good. Maximum penetration obtained is approximately -.5 seconds with a mean effective pene-tration of about . 25 seconds two-way travel time. Navigation was land based (Del Norte Txisponder) . Xt has a system accuracy of 3 meters and the overall accuracy of line locations is about 75 meters. Lines were generally run at 1 kilometer spacing normal to the trend of geologic structures which are oriented subparallel to the coastline. The tight coverage thus allows for detailed mapping of structural trends. The high resolution data was interpreted in conjunction with pre-existing deep penetration reflection profiles (Wagner, 1974), (McCulloch, 1975), (Aquatronics, data collected July 1974), (Bolt, Beranek, and Newman, data collec'ted Dec'ember 1973 and April 1974). Ages have been assigned to four acoustic units based on correlations with work done by Hoskins and Griffiths '(1971), Wagner (1974),

and from dart core samples collected by McCulloch on a 1974 U.S.G.S. cruise. The samples were dated by Dave Bukry, also of the U.S.G.S.

6. My investigations indicate that the San Simeon fault zone is a complex structural break which in general 1 separates Cretaceous basement rocks from a thick section of deformed Tertiary sediments. Reflection profiles I acquired in 1979 in very shallow .near shore areas were interpreted in conjunction with pre-existing offshore profiles and provide data for-detailed study of structural relations of offshore extensions of the San Simeon fault zone. I conclude that:

a) The zone is 2 to 8 km wide and composed of numerous anasto-mosing fault strands, b) The offshore extension of the San Simeon fault zone to the northwest acts primarily as a boundary between Mesozoic basement 'and Tertiary sediments, c) A zone of chaotically deformed. Pliocene sediments lies adjacent a near surface mass of acoustic basement in the area northwest of Pt. Piedras Blancas, d) The southern extension of the San, Simeon fault zone, which may act in part as a boundary between Upper Cretaceous forearc basin deposits (Cambria Slab) and Franciscan assemblage rocks, can be followed approximately 10 km southeastward from San Simeon Bay where it joins a strand of the Hosgri fault zone. A short segment offshore from Cambria is 'nferred due,to the linear trend of the fault to the north-west and southwest of this area. The lack of change in acoustic signature across this segment is probably due to the similar reflection characteristics of the cherty middle Miocene unit

and the Mesozoic unit, e) Refolded en-echelon folds in Miocene sediments are. truncated by the fault on its west side and are consistent with a right lateral shear couple along the fault trend, and f) Although major movement along faults occurred during Miocene and Pliocene time, faulting may be as recent as late Pleistocene or Holocene. Evidence for relatively recent movement includes possible offset of post-Wisconsin sediments (< 20,000 years), and linear trends of landward facing scarps on the sea floor.

7. Xn summary, my recent investigations are inter-preted to indicate that the Hosg'ri and San Simeon fault zones n

represent a continuous and thro'ughgoing fault system.

8. All of the matters herein are known to me of my personal knowledge or of my personal opinion based on my educa-tion, research, and experience. Xf called as a witness, T. am competent and w'ould testify thereto.

Robe.n Bruce Leslie Subscribed and sworn to before me this . S day of February, 1980 OFAQlA'Ryfair.

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'RA'-'Q NOTARY FURLIC.CALIFORNIA a CIli:Iin Sinta C;ua Cnu yy Fain:ln:I tAy Commissioa s Expires !,1ar. 1&. 1s83 NOTARY PUBLIC My commission expires: J~ ~,pm'J>

ATTACHMENT A: Track Chart for Acoustic-Reflection Profiles U. C. Santa Cruz R/V Scammon April 1979 Cruise Central Cali fornia 0 ffshore.

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