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Source processes of the Haicheng, China earthquake from observations of P and S waves

Cipar, John (1979) Source processes of the Haicheng, China earthquake from observations of P and S waves. Bulletin of the Seismological Society of America, 69 (6). pp. 1903-1916. ISSN 0037-1106.

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The Haicheng, China earthquake of February 4, 1975, was the first major seismic event to be predicted. In this paper, long-period teleseismic P waves and S waves from this event are compared directly to time-domain synthetic seismograms to infer the source parameters. Results indicate the focal mechanism of the earthquake is nearly left-lateral strike slip along a northwest striking nodal plane (strike = 288°, dip = 78° N, rake = 342°). The strike of this nodal plane agrees with the trend of the aftershock distribution. Seismic moment is 3 × 10^(26) dyne-cm and source duration is 7 sec. Azimuthal variation of P-wave duration is attributed to fault propagation in a northwesterly direction along the strike of the aftershock zone. A model with a fault length of 22 km and rupture velocity of 3.2 km/sec can explain the observed P waves quite well. There is considerable discrepancy between observed SH waves and synthetics computed using this model. These discrepancies are due to source structure complexities and/or changes of fault mechanism as the rupture propagated along strike. The average dislocation is computed to be 2.8 m and the stress drop is 53 bars.

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Additional Information:© 1979 Seismological Society of America. Manuscript received March 27, 1979. I wish to thank Tom Hanks who originally suggested the research and who assisted in the early phase of the investigation. Wai Ying Chung, John Ebel, Don Helmberger, and Jim Pechmann critically read the manuscript and provided many valuable comments. Chuck Langston generously provided his computer programs for calculating synthetic seismograms. This research was supported by National Science Foundation Grant EAR78-14786.
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Caltech Division of Geological and Planetary Sciences3231
Issue or Number:6
Record Number:CaltechAUTHORS:20140915-094317491
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49695
Deposited By: Tony Diaz
Deposited On:15 Sep 2014 17:29
Last Modified:03 Oct 2019 07:16

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