ML20202G228
| ML20202G228 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 03/25/1986 |
| From: | Pomeroy P RONDOUT ASSOCIATES, INC. |
| To: | Savio R Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1837, NUDOCS 8607150338 | |
| Download: ML20202G228 (6) | |
Text
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RONDOUT ASSOCIATES,
]NCORPORATED IM8W
. O. Box 224. Stone Ridge. New York 12484 PDA i
- -. - 3
- arch 25,1936 p C.
Advisory Com.ittee on Reactor Safeguards g.b ' 4 f.T,,
r U.S. h'aclear Regulatory Comission 1717 il Street IN,10th Floor g
Washington, DC 20555 Att'n:
Dr. Richard Savio
Dear Dr. Savio:
In response to your request, I am pleased to provide the following evaluation of the letter dated 11 March 1985 to the ACRS from the Ohio Citizens for Responsible Energy (OCRE).
The letter makes two basic points:
1.
There is a capable fault in the vicinity of the plant, and 2.
The "best fit" lines through the aftershocks of the January 31st, 1986 event an1 through the historical seismicity aaree with the composite fault plane solution of the aftershocks and thus confirm the fault direction.
I will treat each of these issues separately.
1.
- icst seismologists (including myself) would strongly agree with the OCRE statement that "the earthauake was caused by fault movement".
The key ques-tien that has been litigated extensively is "Which f ault?". The concept of a capable fault was introducef te be used when a specific fault structure could he identified an! associated with movement, macroscismicity or another capable fault.
In the absence of a specific fault structure, the tectonic province approach (utilized at the Perry site and all other plants in the Eastern and Central United States) was required.
That approach, which is more conserva-tive, says, in essence, that since we cannot identify a specific structure, the largest event in the tectenic province should be utilized as the design basin earthquake.
In the Perry case, that was a 5.3 magnitude event (based on avents like the 1929 Attica,.'iY event, the 1937 Anna, OH event and the 1980 Sharpsburg,KYevent). The historic record clearly delineates these events and others as the largest events in this region.
The occurrence of a magni-tude 4.9 event then is not unexpected and the resultant accelerations (below 14 Hz) of the plant were well below the design or SSE levels.
In my judge-ment, the seismicity of the region is adequately accounted for using the tec-tonic province approach (in the absence of any situations that might tend to localize the seismicity, such as fluid injection).
The OCRE letter then goes on to say, "The fault is a right-lateral strike slip 9
fault...".
That sentence, I believe, is based on a misunersti: Hing.
The c
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only available data that bears on that subject is a composite fault plane j
solution based on some of the aftershocks (shown in Figure 1).
If one assumes that the composite fault plane solution is accurate and representative of the j
aftershocks, then these aftershocks are rupturing a fault or faults that are j
either:
i a.
right-lateral strike slip, vertical, Erie striking faults, b.
left-lateral strike slip, vertical Wi4U striking faults, or c.
both.
t Epicentral lccations, discussed below, are about the only information that can j
be used to attempt to distinguish the actual rupture plane from an orthogonal i
" nodal" plane.
i Furthermore, no fault plane solution has yet been determined for the main
(
shock that occurred on 31 January 1986.
Although it is often the case, it remins to be seen whether the main shock ruptured the same wa, the aft-ershocks did.
1 j
i
- 2. The sccond point is sur.ed up by the first sentence of paragraph,
of the l
OCRE letter, "The fault direction appears to be confirmed by observ.d seismi-city". The fault direction is apparently that inferred from the aftershock 4
composite fault planc solution discussed above.
The OCRE Er"'. : t 1 material (apparently based on early locations of six aftershocks by LDG0 personnel is j
quite different than that presented to the ACRS by Weston Geophysical (Figure l
2). The Weston material was based on data from 13 stations and shows the 10 aftershccks and the main shock location (USGS - Dewey and Gordon).
No error e
ellipses are shorn on either figare.
In a telephone conversation with Dr.
Seeber of LDGO, he indicated that a more recent study shows the same linear character ("'iE) about 1 Kn in length, 200m breadth and depths (of well located events) of 4 to 7 km.
Differe,ces beteeen the data for Figure 1 and the later i
LD",0 results can be interpreted as a measure of the uncertainty in location I
that must be resolved by further research. Similarly, Exhibit 2 of the OCRE letter c?n be compared with figure 3, which is the EPRI Data Base for the i
north central portion of the country.
Drawing straight lines on any of these i
maps of epicenters is a hichly suMeetive exercise, particularly in the absence of error ellipses.
Over the past 20-30 years, many competent seism 61-ogists have attenpted to define patterns on figures like tnese but, in most l
l
- cases, the results have been of extremely limited significance. At this f
point, further research is rcquired to deliccate the areal and vertical extent l
ur the aftershocks and potential fault structures in the region.
In my judge-j ment, that research can go forward in tendem with the licensing of the Perry Plant. This concludes my evaluation of the OCRE letter.
I
\\
j I do want to reiterate the points thet I made in the handwritten material I
i gave to you at the close of the ACRS Sub-Committee meeting on Perry.
- j 1.
Long teru seismic monitoring with high quality high sensitivity instru-ments should be carried out in the area (including the aftershock zone and the 4
f injection well area as well as the vicinity of the plant).
4 1,
s 4
2.
We cannot preclude the possibility of a relationship between fluid injec-tion and the seisiic activity in this area. The fluid injection may be the result of the Calhio waste injection wells, solution mining activities and/or gas and oil reccvery.
In any event, a vigorous research program by the USGS and others to investigate the relationship, if any, between injections and the earthquakes, is essential to enhance our understanding.
3.
Thc large higS frequency content of earthquake signals is a generic prob-lem of significance to the successful operation of these plants. At frequen-cics greater t'ian 14 P:, the SSE for Perry was significantly exceeded.
fio significant failures in systems operating at the time of the earthquake have been reportcJ.
Nonetheless, at some,; hat highcr magnitude levels, these high frevency signals will be of importance and a generic study should be under-taken.ith the goal of madifying required response spectra and to insure the cxti.siig safa operatinn of relays, valves anJ othcr devices that can poten-tiell., be affected by t',ese frcquencies.
Tha% you for the opportunity to co.nment on these issues.
Sir.cerely ycurs,
.O M. h.I-M, e.eu P a u l '.l. Pc ercy ACRS Cons.ltant U
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