ML19254D981
| ML19254D981 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/04/1979 |
| From: | Ellen Brown CALIFORNIA, STATE OF |
| To: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19254D982 | List: |
| References | |
| TASK-03-06, TASK-3-6, TASK-RR NUDOCS 7910300386 | |
| Download: ML19254D981 (2) | |
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STATE OF CAUFORNIA-THE RESOURCf 3 AGENCY EDMUND G. BROWN JR., Cowwoe O(PARTMENT OF CON 11RVATION 8
DIVISION OF MINES AND GEOLOGY 189 DIVISION HEADQUARTERS go 1416 P7 NTH STRttT, ROOM 1341 g
SACR MINTO. CA 95814 (Phone 51F.51823)
October 4, 1979 Mr. Robert Jackson Chief, Geosciences Branch U S. Nuclear Regulatory Commission Wae.hgton, D.C.
20555 Suject: Questions Regarding San Onofre Nucler Project by the Division of Mines and Geology
Dear Mr. Jackson:
The staff of the Division of Mines and Geology has reviewed the Woodward-Clyde Consultant's report, " Report of the Evaluation of Maximum Earthquake and Site Ground Motion Parameters Associated with the Offshore Zone of Deformation, San Onofre Nuclear Gener& ting Station, June 1979", in conjunction with the NRC meeting held at Menlo Park on September 13, 1979.
We would appreciate having the following questions included with yourlist o,f questions which are to be presented to the applicant (;c is to be noted that the Division may have other concerns, but the questions in this letter apply only to the WCC study):
1.
Why didn't WCC use conventional methods in estimating the maximum earthquake magnitude such as employed in the Auburn Dam study? Any new method, no m'at'.er how promising, must be tested with the experience of %stablished methods. W form ad sh,e recommend that all methods of acceptable analysis be in tabular ow magnitudes and cccelerations.
2.
What are the limits of uncertainty in the determination of the slip rates for ranges of magnitude? The range of slip rates rather than single values should be plotted. Plotting in this manner could move the maximum earthquake line toward substantially higher values.
3.
Why hasn't the Coronado Barks-Palos Verdes fault been considered in the earthquake analysis? The fault has in excess of 50 feet sea floor offset and shows youthfui and long, continuous fault features (Unpublished report,
" Final Technical Report, USGS, Office of Earthquake Studies, Contract No.
14-08-0001-17699, Kennedy, et al.")
The slip rate on this fault may contra-dict WCC's view that all faults west of the San Andreas fault have lower slip rates with increasing westerly distance.
4.
Has the 1812 Earthquake (M6.5) been considered as bei;ig associated with a local structural source in the analysis of the safe shutdown earthquake?
If such is the case, how does this conclusion affect the determination (CCMG Open File report 79-6 SAC)?
1229 317
'T 910 3 00 3 7 6 Gu
Robert Jackson, NRC 5.
Can the San Miguel fault in Mexico be connected to the Rose Canyon fault with some degree of certainty? The San Miguel fault was apparently the cause of the February 9,1956 earthquake of M6.8 in the area.
If the San Miguel fault is considered as part of the Newport-Ingicwood-Rose Canyon fault system, can the suggested maximum M of 6.5 for this fault system offshore of the San Onofre site therefere be considered too smail?
6.
Because the slip rate approach involves only a small time sample, cannot the trend in figure 7 be derived from a nonrepresentative time window of obser-vation? The WCC approach presumes that the procability of observing the larges + magnitude on a particular fault during a given period is greater for higher rates of seismicity (slip rate).
Is the time period considered in the WWC study of sufficient length to give a meaningful conclusion?
7.
Has the focusing effect been considered in developing the design conclusions for San Onofre reactors 2 and 3? If it has not, we would recommend that NRC and the applicant explore the possible design implications of this phenomenon.
If the focussing effect significantly modifies the design peak acceleration, then does this also materially change the selection of the appropriate design spectra which would be adopted for construction.
8.
The "g-value versus distance" graph (figure 8, Woodward-Clyde report) is compiled from data recorded at a range of about 20 km and 150 km from the epicenter; no data at closer distances were plotted to confinn the graph for the San Onofre site which is assumed to be located 8 to 10 km frcn the postulated epicenter. Therefore, could higher accelerations than shown occur at closer distances in view of the lack of informatich as indicated ch the graph?
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Enclosuro:
Special Publication 54
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