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Empirical Green’s Function Analysis of Recent Moderate Events in California

Hough, S. E. (2001) Empirical Green’s Function Analysis of Recent Moderate Events in California. Bulletin of the Seismological Society of America, 91 (3). pp. 456-467. ISSN 0037-1106. doi:10.1785/0119970154.

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I use seismic data from portable digital stations and the broadband Terrascope network in southern California to investigate radiated earthquake source spectra and discuss the results in light of previous studies on both static stress drop and apparent stress. Applying the empirical Green's function (EGF) method to two sets of M 4–6.1 events, I obtain deconvolved source-spectra estimates and corner frequencies. The results are consistent with an ω^2 source model and constant Brune stress drop. However, consideration of the raw spectral shapes of the largest events provides evidence for a high-frequency decay more shallow than ω^2. The intermediate (≈f^(–1)) slope cannot be explained plausibly with attenuation or site effects and is qualitatively consistent with a model incorporating directivity effects and a fractional stress-drop rupture process, as suggested by Haddon (1996). However, the results obtained in this study are not consistent with the model of Haddon (1996) in that the intermediate slope is not revealed with EGF analysis. This could reflect either bandwidth limitations inherent in EGF analysis or perhaps a rupture process that is not self-similar. I show that a model with an intermediate spectral decay can also reconcile the apparent discrepancy between the scaling of static stress drop and that of apparent stress drop for moderate-to-large events.

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Hough, S. E.0000-0002-5980-2986
Additional Information:© 2001 by the Seismological Society of America. Manuscript received 24 September 1997. I thank Hiroo Kanamori, Tom Heaton, Doug Dreger, Tom Hanks, Bill Joyner, Gail Atkinson, Nancy King, and Art Frankel for helpful discussions in the course of this work and Katrin Hafner for assistance with processing the codes for the Terrascope data. I thank Yoshihas Iio and two anonymous reviewers for helpful comments and very gratefully acknowledge Michael Fehler for his suggestions and patience. The Joshua Tree/Landers GEOS deployment involved the hard work of numerous individuals, including Jim Mori, Gene Sembera, Chris Dietel, Joe Sena, Gary Glassmoyer, and Scott Lydeen, and the helpful cooperation of Ralph Skaggs and Ginny Whitney. The Terrascope data was accessed through the Southern California Earthquake Center data center, which is supported by grants from the National Science Foundation and the United States Geological Survey.
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United States Geological Survey (USGS)UNSPECIFIED
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Record Number:CaltechAUTHORS:20140806-090203196
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Official Citation:S. E. Hough Empirical Green's Function Analysis of Recent Moderate Events in California Bulletin of the Seismological Society of America, June 2001, v. 91, p. 456-467, doi:10.1785/0119970154
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48049
Deposited By: Ruth Sustaita
Deposited On:06 Aug 2014 16:52
Last Modified:10 Nov 2021 18:03

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