ML19254D672
| ML19254D672 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos File:GEH Hitachi icon.png |
| Issue date: | 08/08/1979 |
| From: | Slemmons D AFFILIATION NOT ASSIGNED |
| To: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19254D659 | List: |
| References | |
| NUDOCS 7910290327 | |
| Download: ML19254D672 (3) | |
Text
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Appendix 8 DAVID B. SLEMMONS CCNSUL 71NG GECLCC $7 2995 GCLDEN VALLEY RCAO RENO. NEVACA aS!C6 - (7C2) 972 8877 August 8, 1979 Mr. Rchert E. Jackson, Chief m T:' H 9
O Mg i
D Geosciences Branch Division of Site Safety and g g,
@.d'Ll Environmental Analysis U. S. Nuclear Regulatory Ccemission Washington, D.C. 20555 Cear Mr. Jackson:
During the period from Septa ^ er 21, 1978 to present, I have reviewsd all available reports concern!ng the potential for surface faulting at the General Electr.ic Ccmpany's Test Reacter (GETR) at vallecitos, California.
My evaluation ineludes visits to the site, examination of all trenches that were open for inspection during this period, and one icw-sun angle aerial re-connaissance of the area.
In view of the wide divergence of opinion on the origin and character of the shears at tne site and their relationship to major geologic structures in the region, I have arrived at my opinions slowly, with censideration of all viewpoints that have been expressed.
This letter s- =ri:es my conclusions.
My main sources of documentation include the folicwing basic reports and the publications that are referenced in these reports:
Earth Sciences Associates, 1978a, Geologic investigation, General Electric Test Reactor Site, Vallecitos, California: for General Electric Co., February 1978.
- 1978b, Geologic Investigation, General Electric Test Reactor Site, Vallecites, California:
for General Electric Co., Addendum 1, April 1978.
- 1978c, Landslide s-d ility, General Electric Test Reactor Site, Vallecitos, California:
for General Electric Co., July 1978.
- 1979, Geologic investigation, Phase II, General Electric Test Reactor Site, Vallecitos, California:
for General Ziec--ic Co., February 1979.
- Herd, J.
G.,
- 1977a, Geologic map of the Las Posi:as, Greenville, and Verona faults, eastern Alameda Ccunty, California:
C.
S.
Gecl. Survey Open-file rept.77-689.
19~7b, Map of Ouaternary faulting along -he Eayward and Calaveras * *"' - -- es, Niles and Milpitas 7 i' ruadranglas, California:
7.
S. Seci
- "-"ey Cpen-file rap ~7-643.
1345 32
- e. 3GWW c
0 g
Robert E. Jackson Page 2
- Jahns, R.H.,
1979, Evaluation of seismic hazard at the General Electric Test Reactor Site, California:
for General Electric Ccmpany, February 1979.
U. S. Nuclear Regulatory Cc= mission, 1978, Show cause proceeding, safety Evaluation report input, GE Test Reactor Site /
Vallecitos Nuclear Center, August 17, 1978.
My observations and study of this area leads =e to the conclu-sien that the shears observed in exploratory trenches 3-2, 3-1/
B-3, and E are capable surface faults.
Review of the field data and earthquake. magnitudes of examples of surface faulting through-out the world, including a newly described example of reverse-slip faulting (Rothe and others,1977), confirm the general statement of the U. S. N. R. C (1978) document.
The N.R.C.
staff position is stated on pages 6-9, and my ccaments follow for the numbered conclusions (2) to (5) :
(2)
The overall appearance of the shears, their parallelism, their recurrent activity, and the presence of some strands well in front of the hill front, all support a tectonic origin.
They appear to be par: of a =cne of shears or faults that does not conform exactly with the Verona f ault as mapped by Herd (1977).
The widespread development of dip-slip striations on fault planes suggest a major dip-slip ccmponent that appears to be ancmalous for a fault that is both subparallel to and near the Calaveras fault :ene.
This orientation of striaticas could be the result of a ecmbined fault-ing-folding mechanism, since many of the regional fault and fold structures are of similar strike and since the folding of late
' Cenozoic deposits is widespread in the vicinity of Livermore Valley.
The possible development of shorter faults, or of smaller displace-ment values frem either secondary distributed effects of folding, or from the detachment of surface faults by late Ceno:cic deposits of the deeper, pri=ary f ault displacements appears to =e to be possible, but is not verified or well documented for this area.
(3)
The co nclusion tha: the Verona fault is capable within the meaning of Appendix A to 10 CFR Part 100 is proved by the separa-tions of the =cdern sola by the 3-2, 3-1/3-3, and H shears.
(4)
The N.R.C.
(1978) description of the faults exposed in the exploratory trenches as having the potential for an esti=ated 2.5 meter ne: slip offse: on a reverse-oblique fault with a dip of 100 to 600 is obtained by several mecheds and is supported by both the new explora:Ory trench data and by the curren: worldwide data bank of information on the relationships between earthquake magni-tude to faul: rupture length and maxi =um surface displacement.
The esti= ate is ccmpatible with the curren: ssti=ates of :ccal fault length ( 3. 2 k= :o 12 km), the observed seriations along the shears expcsed by :ne explora:Ory trenches, with striations tha: very fr:m reverse-slip := s t:Lke-slip, and the verldwide fault rup ture data
- Sle== cts, 1377} and the field data f or the San Fernand ear nquake Of 1371 and the II Asnam, Algeria earthquake Of 1354.
The excellen:
dccu=entatica cf of fsets of up to 1.0 meter for the =cdern scia expcsed by the renches defines the =cs: pr:bable fi= ens _cn for a 1345 328
Robert E. Jackson Page 3 future offset.
The lack of definitive offset data for earlier displacements on these shears, and the historic variations between earthquake magnitude and associated amount of offset that occurs during each new event, requires that a larger displacement value be used to provide a conservative estimate of potential offset.
The 2.5 meter net slip value of the N.R.C. report (1978) is reasonable for a fault with a length of between 8.2 and 12 km and the observed 1 m offset of the modern solum; it is consistent with the dispersion of data shown on the worldwide data for earthquake magnitude to maximum displacement relations (Sle= mons, 1977, Figure 25).
The =aximum earthquake magnitude described for the Verona fault
- ene is listed as 6 to 6 4 My review of the possible faulc parameters, the 8.2 to 12 km length, the surface displacement of 1 to 2.5 m, and the San Fernando and El Asnam case histories of 6.4 and 6.7 magnitude, respectively, all indicate a potential magnitude of about 6.5 0.5, for an earthquake generated by f aulting. that is limited to the Verona f ault :ene.
The matter of earthquake recurrence is i=portant if a probabilistic analysis is used for assessing the earthquake risk.
Table A-l of the report by Engineering Decisien Analysis Company (1979, Probability analysis of surface rupture offset beneath reactor building, General Electric Test Reactor: for General Electric Co.) indicates that the three shears, 3-2, 3-1/3-3, and H, have cumulative offsets of more than 80, 40 and 20 feet respectively.
This amount of offset, if it occurred in the inferred 70 to 195,000 yr period i= plies a high frequency of earthquakes if each event involves an average displacement of 1 m.
Alternatively, if longer recurrence intervals are used, then the average offset is likely to be much greater than 1 m, or the offset at depth could be much greater.
I recommend that your staff position be an up-dated modification of the August 17, 1978 report.
The new data does not suggest a need for substantial changes in rationale or content frem the basis used in the earlier report.
Sincerely yours, b.k. - '
c Cavid 3. Sle== ens Consulting Geologist i345 329