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Constraints on Temporal Variations in Velocity near Anza, California, from Analysis of Similar Event Pairs

Haase, Jennifer S. and Shearer, Peter M. and Aster, Rick C. (1995) Constraints on Temporal Variations in Velocity near Anza, California, from Analysis of Similar Event Pairs. Bulletin of the Seismological Society of America, 85 (1). pp. 194-206. ISSN 0037-1106.

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Similar earthquake pairs recorded by the Anza Seismic Network in southern California are used as repeatable sources to place an upper limit on temporal changes in seismic velocity which occurred in the vicinity of the Anza seismic gap in the last 9 yr. Relative arrival times for each pair of events are found using a cross-correlation method and relative locations are calculated to verify that the pairs have nearly identical hypocenters. The time separation between events in these pairs varies from less than a day to almost 7 yr. The long-term changes in seismic travel times, as measured from the pairs with the longest time separation, are not significantly greater than the noise level estimated from the short-time-separation event pairs. Almost all P-wave paths show less than 0.06% (0.007 sec) change in travel time and all S-wave paths have less than 0.03% (0.004 sec) change. Sensitivity tests place an upper bound on travel-time changes that could be compensated by hypocenter mislocation at 0.2%. There is no evidence that localized stress accumulation causes measurable changes in seismic velocity in the Anza region.

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Shearer, Peter M.0000-0002-2992-7630
Additional Information:© 1994, by the Seismological Society of America. Manuscript received 6 July 1993. Funding for this study was provided by USGS Grant Numbers 14-08-0001-G1767, 1434-93-G-2295, and 1434-92-G-2202. The authors would like to thank Frank Vernon for his interest and support in this project and his help in working with the Anza Network dataset.
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Official Citation:Jennifer S. Haase, Peter M. Shearer, and Rick C. Aster Constraints on temporal variations in velocity near Anza, California, from analysis of similar event pairs Bulletin of the Seismological Society of America, February 1995, v. 85, p. 194-206
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48043
Deposited By: Ruth Sustaita
Deposited On:06 Aug 2014 16:10
Last Modified:03 Oct 2019 06:59

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