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Temporal changes in P-wave velocity in Southern California

Kanamori, Hiroo and Chung, Wai-Ying (1974) Temporal changes in P-wave velocity in Southern California. Tectonophysics, 23 (1-2). pp. 67-78. ISSN 0040-1951. doi:10.1016/0040-1951(74)90111-5.

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P-wave delays at Tinemaha, China Lake, Pasadena, Riverside, Hayfield and Barrett, stations of the CIT Southern California seismic network, are measured for three explosions in the Aleutians and six deep-focus earthquakes in the Marianas. Except at Riverside, no change in P-delays exceeding the experimental uncertainty, ± 0.2 sec, is found during the period from 1965 to 1971. At Riverside, however, P-delay in 1971 is at least 0.4 sec smaller than that in 1965, indicating a temporal P-velocity increase beneath Riverside from 1965 to 1971. Evidence supporting this result is obtained from the P-times at Riverside for quarry blasts at Corona (Δ ≈ 20 km). Precise travel-time measurements are made for eight blasts since 1949. The travel time changes as a function of time, ranging from 3.3 to 3.7 sec. This range of variation seems to be larger than the experimental uncertainty. The trend for the period from 1964 to 1969 is consistent with the temporal change in the teleseismic P-delays observed at Riverside. The observed change in P-delays is not related in any obvious way to past seismic activity; rather it might represent a large-scale fluctuation of the property of the crust caused possibly by change in the tectonic stress and fluid-vapor flow, and may be related to future earthquake activity.

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Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1974 Published by Elsevier B.V. Received 1 October 1973, Accepted 24 January 1974, Available online 8 April 2003. Contribution No. 2395, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, Calif. This research was supported by U.S. Geological Survey Contract No. 14-08-0001-G52, Am. 1. We wish to acknowledge helpful discussions with Clarence Allen, Don Anderson and Donald Helmberger. We are indebted to Francis Lehner and Ralph Gilman for acquisitions of the field data. We are grateful to Minnesota Mining and Manufacturing Company at Corona, Calif., California Portland Cement Company at Mojave, Calif., and General Portland Incorporated, Lebec, Calif., for kind cooperation in this study.
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Caltech Division of Geological and Planetary Sciences2395
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Official Citation:Hiroo Kanamori, Chung Wai-ying, Temporal changes in P-wave velocity in Southern California, Tectonophysics, Volume 23, Issues 1–2, July 1974, Pages 67-78, ISSN 0040-1951, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54929
Deposited By: Ruth Sustaita
Deposited On:18 Feb 2015 17:12
Last Modified:10 Nov 2021 20:39

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