ML16341A019
| ML16341A019 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/29/1984 |
| From: | Page B Advisory Committee on Reactor Safeguards, STANFORD UNIV., STANFORD, CA |
| To: | Okrent D, Savio R Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1749, NUDOCS 8406210566 | |
| Download: ML16341A019 (4) | |
Text
STANFORD UNIVERSITY SThNFORD, ChUFORNlh 94305 H'hRTRFhT OF GEOLOGY oC Eanh Scknces P. EC; c
TELEPHONE: (4Z3) 497-2537 Dz-. Devi6 6hz ent Dz. Ri,chard Savio":
AORS, MC, Keshington, DC
Dear Dave and Dich:
The following remark pertain to the findings of Dr. James Crouch et al.,
as pzesente6 at the meeting he16 in Los Angeles on Ray 24, 'i984 ~
Kin oonclusionsz
- 1. I third the staff's draft elements for the Diablo Canyon L5.oense Cond5tion are very good indeed.
They appear t,o provide logice1 proce6ures for 6eeling with the seismotectonic pz oblems that, are now ar5.s5ng end those that m y arise in the future. There will surely be e nearly oontinuous 5nflow of diet,e.
- 2. At the
- p. esent moment, the latest findings (published by Crouch et a1.)
regarding the Hosgri end other offshore faults 6o not necessarily increase
'the maximm ground mo ion the m5.ght be experienced by the Di.eblo Canyon
- plan, end do not neoesserily increese the frequency of strong eeMquakes.
As mo. e in ormetion is acquired, the implioetions could be either moze favorable or less favorable t,o the perceive6 safety of the plant.
Further cozmentsz If the offshore Hosgri fault dips landward beneath the Diablo Canyon plan, the ver icel dis ence from the site to the fault, could be either greeter:or
'3.ess hen the horizon al distance from the plant to the su<ace trace of the fault, diepending on the curveture of the feu1t, profile, which has not been es eblished.
In any ease, it, "s highly unlMely that a stz.ong earthque>
e would be geziere e6 et e depth less then 8-10 3',
as a certa5.n amount of confining pressu e is. equired. If the Hosgri fault were to pess uzider the plant at e vertical d5.stence of o M, sey, 5t would be totally unrealistic to postulate e s rong eerthque3:e s e~ng from the fault directly benee h the plant The moderate to inconspicuous 6is urbence of the uppermost strata neer the Hosgri feult, as seen 5n Dr. Crouch's reflection p. ofiles, woad argue f'r very infreouen~
(o very smell) slip-events if the Hosgr5. fa's largely a th. ust fault. However, we must, not be to'o optimis ic, as we ~illdo not liow for su;e whet the size and recurrence 5.nterval e.>>e for slip-events on the fault.
A downwe d-f1e tening, thrust-live configuration would me>e it high
~,g gq5s s~G
unli3.ely that the Hosgri fault has accrued 80-150 3an of stri3".e-slip, The fault would be oharacterized by predominan thrust-or oblique-slip, and the vibratory motion might differ somewhat from that which has been envisioned for the Diablo Canyon site. Fihether the SSE and the ground mo ion would be more seve. e or less severe rema'Lns to be seen. It aey tu n out that, if all other factors were equal, an SSE from e thrust fault would be more'evere than an SSE from a stri3 e-slip fault, However, if the Hosgri fault is really a thrust fault, the "new" Hosgri may be shorter than the "old" Hosgri fault. It may not be a part of the San Gregorio zone, after all. It m y not have a history of large slip-events.
So, the various facto;s, when combined, may give a result compatible with the earlier postulations.
Sincerely, Benjamin H. Page Copies sent to each add essee.