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Effects of lateral heterogeneity and source process time on the linear moment tensor inversion of long-period Rayleigh waves

Nakanishi, Ichiro and Kanamori, Hiroo (1982) Effects of lateral heterogeneity and source process time on the linear moment tensor inversion of long-period Rayleigh waves. Bulletin of the Seismological Society of America, 72 (6). pp. 2063-2080. ISSN 0037-1106.

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Spectra of mantle Rayleigh waves recorded on the IDA network are inverted to determine the seismic moment tensor of the 9 June 1980 California-Mexico Border earthquake, the 29 July 1980 Vanuatu Islands earthquake, and the 9 July 1980 Santa Cruz Islands earthquake. Examinations are made to correct for phase velocity lateral heterogeneity and source process time. A simple regionalization (stable continent, tectonic region, young ocean, and old ocean) improves results of the linear inversion, but the phase correction is not large enough, and the discontinuous change of phase velocity across the boundary between regions causes an artificial rapid change in apparent phase velocity as a function of azimuth. Therefore, a more detailed but gradual representation of the lateral heterogeneity is desirable to correct for the propagation effect in the linear inversion. A source process time which consists of the nondirectional part of the apparent duration of main faulting and the delay time of the faulting from initial break is estimated by a phase analysis of Rayleigh waves. The source process time is generally proportional to the seismic moment on the log-log scale, but some earthquakes deviate considerably from the general relation. Therefore, the measurement of the source process time should be made before the moment tensor inversion. The phase errors introduced by the lateral heterogeneity and source process time may cause a bias to low scalar moment.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1982 by the Seismological Society of America. Manuscript received 14 April 1982. The IDA data used in this study were made available to us by courtesy of the IDA project team at the Institute of Geophysics and Planetary Physics, University of California, San Diego. We would like to thank Jeff Given for reviewing the manuscript. We thank Adam Dziewonski and Joseph Steim for a preprint of their paper. We appreciate suggestions made by Howard Patton as a reviewer of the manuscript. We thank Laszlo Lenches for drafting the figures. We thank Lynn Finger for typing the manuscript. This research was supported by the U.S. Geological Survey Contracts 14-08-0001-19755 and 14-08-0001-19265 and the National Science Foundation Grant EAR-811-6023.
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Caltech Division of Geological and Planetary Sciences3759
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ID Code:49246
Deposited By: Tony Diaz
Deposited On:04 Sep 2014 20:19
Last Modified:09 Mar 2020 13:18

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