Earthquake recurrence rate estimates for eastern Washington and the Hanford Site
The historical and instrumental records of earthquakes were used to estimate earthquake recurrence rates for input to a new seismic hazard analysis at the Hanford Site in eastern Washington. Two areas were evaluated, the eastern Washington region and the smaller Yakima Fold Belt, in which the Hanford Site is located. The completeness of a catalog of earthquakes was evaluated for earthquakes with Modified Mercalli Intensity (MMI) IV through VII. Only one MMI VII earthquake was reported in the last 100 years in eastern Washington. The reporting of MMI VI earthquakes appears to be complete for the last 80 years, and the reporting of MMI V earthquakes appears to be complete for the last 65 years. However, MMI IV earthquakes are consistently under-reported. For a limited set of earthquakes, both MMI and magnitude (M/sub L/) have been reported. A plot of these data indicated that the Gutenberg-Richter relationship could be used to estimate earthquakes magnitudes from intensities. A recurrence curve for the historical earthquake data was calculated using the maximum likelihood method, including corrections for the width of the magnitude conversion. The slope of the recurrence curve (i.e., b-value) was found to be -1.15. Another catalog, one that listed instrumentally detected earthquakes from 1969 to the present, was used to supplement the historical earthquake data. Magnitudes were determined using a coda-length method (M/sub c/) that had been approximately calibrated to local magnitude M/sub L/. For earthquakes whose M/sub c/ was between 3 and 5, the b-value ranged from -1.07 to - 1.12. 12 refs., 9 figs., 9 tabs.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5856847
- Report Number(s):
- PNL-6956; ON: DE89016579
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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