ML20210S476

Discusses ACRS Consideration of Regional Tectonics of Pacific Northwest.Studies Being Performed Will Better Identify Seismic Potential of Various Regions within Pacific Northwest

ML20210S476
Person / Time
Site:	Washington Public Power Supply System
Issue date:	11/15/1977
From:	Bender M Advisory Committee on Reactor Safeguards
To:	Gossick L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
Shared Package
ML20210S468	List: ML20210S466 ML20210S476
References
CON-WNP-1400 NUDOCS 8605290203
Download: ML20210S476 (3)

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UNITED STATES y) se i

NUCLEAR REGULATORY COMMISSION a '

l ADVISORY COMM'iTTIE ON REACTOR SA FFGUARDS

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VVASHlhGioN, D. C. 20665 November 15, 1977 Mr. Lee V. Gossick Executive Director for Operations U. S. Nuclear Regulatory Comission Washington, DC 20555 SUR7ECI: REGIONAL TEC'lWICS OF ' DIE PACIFIC NORDMEST

Dear Mr. Gossick:

The Advisory Comittee on Reactor Safeguards mt and considered matters related to the regional tectonics of the Pacific Nortnwest at its 209th and 211th meetings. Subcomittee meetings have been held on this subject on Septaber 1-2, 1977 in San Francisco, California and on October 27-28, 19'7 in Portland, Oregon. Tne Comittee and its consultants have had the tvenefit of presentations on this matter by representatives of the Nuclear Regulatory Comission (NRC) Staff, the U. S. Geological Survey (USGS),

Puget Sound Power and Light Coupany, Portland General Electric Conpany, Washington Public Power Supply System, their consultants, and members of the public.

The Comittee and its consultants have given extensive consideration to tne possible intensity of the 1872 Wenatchee earthquake. The USGS, as a consequence of the manner of application of the Modifiec Mercalli (MM) criteria, considers that the assigned intensity of this earthquake cannot be less than MM Intensity VIII and is probably fM Intensity IX, based pri-marily on the occurrence of a large landslide at Ribbon Cliffs, believed to have been caused by this earthquake. This higher intensity differs from the previously cited Intensity of VII - VIII, usually given in prior studies and discussed in the Coonbs Review Panel Report. The Comittee and its consultants have considered this matter and have concluded that the 1872 Wenatchee earthquake should be considered as an Intensity VIII.

In reaching tnis conclusion, the Comittee considered the bases on which the relation cetween MM intensity and horizontal ground acceleration re-lationships were derived. The Comittee remgnizes that higher MM inten-sities of ten are reported when seismic data are scanty and ultiple MM criteria cannot ce used. The extensive data conpiled by the utilities and their consultants nave been reviewed by the ACRS and its consultants.

These data pertain not only to the 1872 earthquake but also to the region-al tectonics, regional geology, and the various mechanisms considered responsible for the seirnic events observed throu3 out the Pacific North-h l

west. Based on a review of tnese data, the Comittee agrees with the i

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Mr. Lee V. Gossick November 15, 1977 opinions expressed Dy most participants and ACRS consultants that arbitrary novement over extenced distances of a prototype 1872 earthquake, for pur-poses of seismic design, should be reexamined. Tnis is particularly true for tne Columbia Plateau whi:n appears to ce eitner a different tectonic province than that in which the 1872 earthquake occurred, or a region of lower seimic activity with regard to frequency and intensity.

Tne Comittee believes that the studies currently being performed on the tectonics of the Pacific Northwest will better identify the seismic po-tential of the various regions within the Pacific Northwest. The studies being performed for the Columbia Plateau Region are particularly prom-ising with respect to oetter defining its seismic potential. The Commit-tee wishes to be kept informed of the progress of these studies and to discuss these matters with the NRC Staff when they have conpleted their review.

Sincerely yours, M. Bender Chairman Ieferences:

1.

H. A. Coonbs, " Report of the Review Panel on the Decenter 14, 1872 Earthquake," dated Decemoer,1976.

2.

Puget Sound Power and Light Company: " Preliminary Safety Analysis Report for Skagit Nuclear Power Project, Units 1 and 2," Cnapter 2.5 and Appendix 2J, " Investigation of tne Deceaber 14, 1672 Eartnquake in the Pacific Northwest," by Bechtel Corporation, Inc., dated June, 1975.

3.

Portland General Electric Cortpany: " Preliminary Safety Analysis Report for Peoble Springs Nuclear Plant, Units 1 and 2," Cnapter 2.5.

4.

Washington PuDlic Power Supply Systems: " Preliminary Safety Analysis Report for WPPSS Nuclear Power Projects 1 and 4," Cnapter 2.5 and Amendment 23.

5.

Weston Geophysical Research, Inc., "Tne 1872 Earthquake - Significant Data and Conclusions," urdated.

6.

WoodVard-Clyde Consultants, " Review of the Pacific Northwest Earth-quake of December 14, 1872," undated.

7.

N. H. Scott, " Evaluation of the Epicenter and Intensity of the Pacific Northwest Earthquake of Decemoer 14, 1872," dated Septemoer 13, 1976.

3 y

Mr. Lee V. Gossick November 15, 1977 8.

Shannon and hilson, Inc., " Reconnaissance Investigation of the Ribbon Cliff Landslide, Entiat, Cnalan County, Washington," dated August, 1976.

9.

Shannon and Wilson, Inc., " Geologic Studies of Columbia River Basalt Structures and Age of Deformation, The Dalles-unatilla Region, Wash-ington and Oregon, Boardman Nuclear Project," dated November,1973.

10. Shannon and Wilson, Inc., " Regional Geologic and Seismic Investiga-tions, Boardman Nuclear Project," dated January,1973.

11. Letters from D. L. Renberger, Washington Public Power Supply System, to O. L. Parr, Office of Nuclear Reactor Regulation, dated Septenber 14, 1977 and September 2,1977, respectively, concerning the results of field investigation of the Fraser River - Straight Creek Fault Zone.

12.

E. S. Cheney, " Interim Report on the Seismic and Geologic Hazards to the Proposed Skagit Power Site, Sedro Wooley, Washington," Revision of Octooer, 1977, unpublished manuscript.

13.

U. S. Geological Survey, "A Study of Earthquake Losses in the Puget Sound, Washington Area," Open File Report 75-375, dated 1975.

14.

U. S. Geological Survey, " Maximum Intensity of the Washington Earth-qaake of December 14, 1872," dated April 1, 1977.

15.

U. S. Geological Survey, " Status of Review - Skagit, Washington," by W. Hays and S. Brockman, dated July 21, 1977.

16. Portland General Electric Conpany: " Final Safety Analysis Report for the Trojan Nuclear Plant," Chapter 2.5.

17. Washington Puolic Power Supply System: " Preliminary Safety Analysis Report for WPPSS Nuclear Project No. 2," Chapters 2.6 and 2.7.

18. Letter from Edson G. Case, Acting Director, Office of Nuclear Reactor Regulation, to R. F. Fraley, Executive Director, Advisory Comnittee on Reactor Safeguards concerning the review of tne geology and seis-mology for the _SKagit Nuclear Project, dated July 28, 1977.

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