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Large-amplitude Moho reflections (SmS) from Landers aftershocks, southern California

Mori, Jim and Helmberger, Donald (1996) Large-amplitude Moho reflections (SmS) from Landers aftershocks, southern California. Bulletin of the Seismological Society of America, 86 (6). pp. 1845-1852. ISSN 0037-1106.

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Closely spaced aftershocks of the 28 June 1992 Landers earthquake (M_w 7.3) were used to make event record sections that show the transverse components of S and SmS arrivals at a distance of 70 to 170 km. For the data recorded toward the north in the Mojave desert, large SmS phases are observed with amplitudes 2 to 5 times greater than the direct S. For similar distances to the south, the SmS arrival is comparable to or smaller than the S. Comparisons to synthetic seismograms indicate that the large-amplitude SmS phases are produced by the simple crustal structure of the Mojave desert that allows a large Moho reflection. In contrast, the more complex geologic structure to the south partitions the seismic energy into a more complicated set of seismic phases, so that the Moho reflection is diminished in amplitude. The large SmS phases observed in the Mojave enhance the overall ground motions by a factor of 2 to 3. This suggests that when damaging earthquakes occur in other regions of simple crustal structures, Moho reflections will produce amplified strong motions at distance ranges around 100 km depending on the local structure.

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Additional Information:© 1996 by the Seismological Society of America. Manuscript received 12 September 1995. We thank H. Benz, G. Fuis, R. Herrmann, and P. Somerville for useful comments on this article. Waveform data were retrieved from the Southern California Earthquake Center Data Center. Partial funding for this project was provided by the Nuclear Regulatory Commission and by the U.S. Geological Survey, Grant 1434-93-G-2322. Contribution 5570, Division of Geological and Planetary Sciences, California Institute of Technology.
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Nuclear Regulatory CommissionUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences5570
Issue or Number:6
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35926
Deposited By: Tony Diaz
Deposited On:11 Dec 2012 23:47
Last Modified:03 Oct 2019 04:33

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