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Shear-wave travel times and amplitudes for two well-constrained earthquakes

Hart, Robert S. and Butler, Rhett (1978) Shear-wave travel times and amplitudes for two well-constrained earthquakes. Bulletin of the Seismological Society of America, 68 (4). pp. 973-985. ISSN 0037-1106.

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The wave-form correlation technique (Hart, 1975) for determining precise teleseismic shear-wave travel times is extended to two large earthquakes with well-constrained source mechanisms, the 1968 Borrego Mountain, California earthquake and the 1973 Hawaii earthquake. A total of 87 SH travel times in the distance range of 30° to 92° were obtained through analysis of WWSSN and Canadian Network seismograms from these two events. Major features of the travel-time data include a trend toward faster travel times at a distance of about 40° (previously noted by Ibrahim and Nuttli, 1967; Hart, 1975); another somewhat less pronounced trend toward faster times at about 75°; a +6 sec base line shift, with respect to the Jeffreys-Bullen Table, for the Borrego Mountain data; and large azimuthally-dependent scatter for the Hawaiian data, probably reflecting dramatic lateral variations in the near-source region. When azimuthal variations in the Hawaii data are removed, the travel times from both events show very low scatter. The correlations were also used to investigate SH amplitudes for possible distance dependence in the data and variations in t_β*. The Borrego Mountain data show very low scatter and no discernible distance dependence. All of the data are compatible with a value of t_β* = 5.2 ± 0.5. The amplitudes from the Hawaii earthquake show the same azimuthal variations found in the travel-time data. When those effects are removed, the Hawaii data satisfies a value of tβ* equal to 4.0 ± 0.5 and, as with the other data set, no distance dependence is apparent.

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Additional Information:Copyright © 1978, by the Seismological Society of America. Manuscript received November 18, 1977. The authors thank David Hadley for critically reading the manuscript. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Office of Scientific Research under Contract F49620-77-C-0022. Rhett Butler was supported by a Fannie and John Hertz Foundation Fellowship.
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Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F49620-77-C-0022
Fannie and John Hertz FoundationUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences2999
Issue or Number:4
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ID Code:48512
Deposited By: George Porter
Deposited On:14 Aug 2014 16:21
Last Modified:03 Oct 2019 07:04

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