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A discrepancy between long- and short-period mechanisms of earthquakes near the Long Valley caldera

Wallace, Terry C. and Given, Jeffrey W. and Kanamori, Hiroo (1982) A discrepancy between long- and short-period mechanisms of earthquakes near the Long Valley caldera. Geophysical Research Letters, 9 (10). pp. 1131-1134. ISSN 0094-8276. doi:10.1029/GL009i010p01131.

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The largest events in the 1980 Mammoth Lakes earthquake sequence show a discrepancy between fault mechanisms which are determined on the basis of the local short-period first motions and those determined by modeling of long-period regional and teleseismic waveforms. The short-period solutions are left-lateral strike-slip on north-striking, near vertical planes. The long-periods invariably require a much more moderately dipping fault plane with a significant dip-slip (normal) component. Persistence of disagreements between short- and long-period polarities to teleseismic distances suggests that the source-time functions are complicated and may be responsible for at least part of the discrepancy. In addition, there seems to be a systematic difference between local short-period polarities and teleseismic long-period polarities that is related to travel paths across portions of Long Valley Caldera. It is possible that a low velocity zone related to recent magmatic activity is causing the deflection of local seismic rays, thus distorting the fault plane projection.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1982 American Geophysical Union. Received July 21, 1982; accepted August 23, 1982. We appreciate the review of this manuscript by L. Burdick, D. Hill, J. Pechmann and M. Walck. We also would like to thank J, Savage for a preprint of his paper. This research was supported by the U. S. Geological Survey Contract Nos. 14-08-0001-19755 and 14-08-0001-19270. Contribution Number 3828, Divsion of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125.
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Caltech Division of Geological and Planetary Sciences3828
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Deposited On:05 Nov 2014 00:11
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