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First motions from seismic sources near a free surface

Burridge, R. and Lapwood, E. R. and Knopoff, L. (1964) First motions from seismic sources near a free surface. Bulletin of the Seismological Society of America, 54 (6). pp. 1889-1913. ISSN 0037-1106.

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The radiation patterns of first motions are calculated for the sudden occurrence of an arbitrarily oriented fault (dislocation) at the surface of a half space; the dislocation in the fault plane is also arbitrarily oriented and is assumed to occur over a very small area of the fault plane. Initially the source is considered at a finite depth and the solution is obtained by allowing the depth to tend to zero. In general the results show a surprising directionality for the radiation of SV. In the focal plane projection the first motions of P and SH for a strike-slip fault show the familiar four-lobed radiation patterns. The first motions of SV show some reversals in polarity with angular distance from the source. The first motions for all components of motion for a dip-slip fault have characteristics governed strongly by the presence of the free surface, and hence differ markedly from the usual radiation patterns for a deeply imbedded source.

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Additional Information:Copyright © 1965, by the Seismological Society of America. Manuscript received August 14, 1964. This research was supported, in part, by research grant No. AF-AFOSR-710-64 of the Air Force Office of Scientific Research as part of the Advanced Research Projects Agency project VELA UNIFORM. One of the authors (E.R.L.) participated in his work as the recipient of an N.S.F. Senior Foreign Scientist Fellowship.
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Air Force Office of Scientific Research (AFOSR)AF-AFOSR-710-64
Advanced Research Projects Agency (ARPA), project VelaUNSPECIFIED
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Caltech Seismological Laboratory1286
University of California, Los Angeles, Institute of Geophysics394
Issue or Number:6
Record Number:CaltechAUTHORS:20140811-130607651
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48309
Deposited By: George Porter
Deposited On:12 Aug 2014 14:38
Last Modified:03 Oct 2019 07:02

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