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Published August 1978 | Published
Journal Article Open

t* for S waves with a continental ray path

Burdick, L. J.

Abstract

The purpose of this study was to determine t* for S waves with ray paths under the continental United States. The data set consists of long- and short-period body waves from the Borrego Mountain earthquake as observed in the northeastern U.S. The P wave forms are dominated by the sP phase and the SH wave forms by the sS. It is assumed that there are no losses in pure compression so that the relative attenuation rate of P and S waves is known. The initial source radiation is determined from the sP phase and the value of t_β* from the spectral content of the S wave. The results indicate that t_β* is 5.2 ± 0.7 sec along this ray path. Long- and short-period body waves from some deep South American events are used to test for lateral asymmetry of the Q distribution under the U.S. No lateral amplitude variation exists in this data, but this result is difficult to correlate with many previous results. The t_ β* value for a 600-km deep earthquake appears to be about 3 sec. A comparison of these values with values computed from current models of the Earth's Q distribution indicates that the models are slightly too high in Q overall and that more of the total body-wave attenuation occurs above 600 km than is indicated by the models.

Additional Information

Copyright © 1978, by the Seismological Society of America. Manuscript received November 14, 1977. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Scientific Research under Contract F44620-72-C-0078. The author is grateful for the advice and assistance of Dr. D. V. Helmberger and Rhett Butler which helped considerably in the completion of this work.

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Created:
August 19, 2023
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