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Internal structure of the San Jacinto fault zone in the trifurcation area southeast of Anza, California, from data of dense seismic arrays

Qin, L. and Ben-Zion, Y. and Qiu, H. and Share, P.-E. and Ross, Z. E. and Vernon, F. L. (2018) Internal structure of the San Jacinto fault zone in the trifurcation area southeast of Anza, California, from data of dense seismic arrays. Geophysical Journal International, 213 (1). pp. 98-114. ISSN 0956-540X. http://resolver.caltech.edu/CaltechAUTHORS:20180208-083541297

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Abstract

We image the internal structure of the San Jacinto fault zone (SJFZ) in the trifurcation area southeast of Anza, California, with seismic records from dense linear and rectangular arrays. The examined data include recordings from more than 20 000 local earthquakes and nine teleseismic events. Automatic detection algorithms and visual inspection are used to identify P and S body waves, along with P- and S-types fault zone trapped waves (FZTW). The location at depth of the main branch of the SJFZ, the Clark fault, is identified from systematic waveform changes across lines of sensors within the dense rectangular array. Delay times of P arrivals from teleseismic and local events indicate damage asymmetry across the fault, with higher damage to the NE, producing a local reversal of the velocity contrast in the shallow crust with respect to the large-scale structure. A portion of the damage zone between the main fault and a second mapped surface trace to the NE generates P- and S-types FZTW. Inversions of high-quality S-type FZTW indicate that the most likely parameters of the trapping structure are width of ∼70 m, S-wave velocity reduction of 60 per cent, Q value of 60 and depth of ∼2 km. The local reversal of the shallow velocity contrast across the fault with respect to large-scale structure is consistent with preferred propagation of earthquake ruptures in the area to the NW.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/gji/ggx540DOIArticle
https://academic.oup.com/gji/article/213/1/98/4757070PublisherArticle
ORCID:
AuthorORCID
Ben-Zion, Y.0000-0002-9602-2014
Ross, Z. E.0000-0002-6343-8400
Additional Information:© 2017 the Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2017 December 15. Received 2017 November 26; in original form 2017 May 29. Published: 18 December 2017. We are grateful to Bud Wellman for allowing us to deploy the instruments on his property. The study was supported by the National Science Foundation (grant EAR-1620601) and the Department of Energy (awards DE-SC0016520 and DE-SC0016527). The seismic instruments of the dense rectangular array were provided by Nodal Seismic with help from Dan Hollisand and Mitchell Barklage. The seismic instruments of the linear array were provided by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech. The facilities of the IRIS Consortium are supported by the National Science Foundation under Cooperative Agreement EAR-1261681 and the DOE National Nuclear Security Administration. The manuscript benefitted from comments of two anonymous referees.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR-1620601
Department of Energy (DOE)DE-SC0016520
Department of Energy (DOE)DE-SC0016527
NSFEAR-1261681
Subject Keywords:Body waves, Earthquake dynamics, Guided waves, Interface waves, Rheology and friction of fault zones, Continental tectonics: strike-slip and transform
Record Number:CaltechAUTHORS:20180208-083541297
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180208-083541297
Official Citation:L Qin, Y Ben-Zion, H Qiu, P-E Share, Z E Ross, F L Vernon; Internal structure of the San Jacinto fault zone in the trifurcation area southeast of Anza, California, from data of dense seismic arrays, Geophysical Journal International, Volume 213, Issue 1, 1 April 2018, Pages 98–114, https://doi.org/10.1093/gji/ggx540
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84738
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Feb 2018 18:29
Last Modified:08 Feb 2018 18:29

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