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Observations of multiple seismic events

Pilant, W. L. and Knopoff, L. (1964) Observations of multiple seismic events. Bulletin of the Seismological Society of America, 54 (1). pp. 19-39. ISSN 0037-1106.

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Two or more dispersed wave trains each with constant amplitude will interfere giving a resultant wave train which is amplitude modulated, if the individual waves have their principal energies in a common frequency band and if the trains arrive with time separations small compared to their total length. The dispersive characteristics of the trains need not be the same. If the component trains are of comparable magnitude, the modulation due to interference becomes significant and a "beat" phenomenon occurs. Multiple trains of dispersed seismic surface waves may occur because of a temporal and/or spatial distribution at the source or because of multipath propagation. Each of these causal mechanisms influences the amplitude and phase spectra of the resultant wave train; derived properties such as phase velocities and amplitude ratios are also influenced. In the case of multipath propagation, wavelength dependent time delays may occur. Two cases of twin earthquakes are analyzed, and the significant features of interference are demonstrated. In one case, estimates are obtained for the amplitude ratio and time delay of the second shock with respect to the first. The interpretation of seismograms and spectra influenced by multiple events is discussed.

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Additional Information:Copyright © 1964 by the Seismological Society of America. Manuscript received October 18, 1963. This research was supported by grant AF-AFOSR-26-63 of the Air Force Office of Scientific Research as part of the Advanced Research Projects Agency project Vela. We would like to thank Drs. M. Nail Toksoz, Ari Ben-Menahem and David Harkrider for their kind permission to use figures 20 and 21. We would like to acknowledge the assistance of Mr. Laszlo Lenches in the preparation of graphical material.
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Air Force Office of Scientific Research (AFOSR)AF-AFOSR-26-63
Advanced Research Projects Agency (ARPA), project VelaUNSPECIFIED
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Caltech Division of Geological Sciences1211
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47771
Deposited By: George Porter
Deposited On:01 Aug 2014 16:47
Last Modified:03 Oct 2019 06:56

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