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Internal structure of the San Jacinto fault zone at Jackass Flat from data recorded by a dense linear array

Qiu, H. and Ben-Zion, Y. and Ross, Z. E. and Share, P.-E. and Vernon, F. L. (2017) Internal structure of the San Jacinto fault zone at Jackass Flat from data recorded by a dense linear array. Geophysical Journal International, 209 (3). pp. 1369-1388. ISSN 0956-540X. doi:10.1093/gji/ggx096.

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The internal structure of the Clark fault in the trifurcation area of the San Jacinto fault zone is imaged using seismograms recorded by a dense linear array (Jackass Flat, JF) crossing the surface trace of the fault and an adjacent array (TR) to the SW. Delay times between phase arrivals associated with ∼3500 local earthquakes and nine teleseismic events are used to estimate velocity variations within the arrays. The teleseismic P waves travel faster beneath the TR than the JF array, in contrast to larger scale tomographic results. Statistical analysis of local P-wave delay times indicates that the entire JF array, with an aperture of ∼400 m, is inside a low-velocity damage zone. This low-velocity zone is bounded on the NE side by a shallow bimaterial interface generating fault zone head waves, and it contains an inner zone of more intense damage generating fault zone trapped waves. The P-wave velocity contrast across the local bounding bimaterial interface is 10–15 per cent. The trapping structure is associated with a width of ∼200 m, S-wave velocity reduction of ∼35 per cent with respect to the surrounding rock, Q-value of ∼20 and depth of ∼3.5 km. The imaging results suggest that the main seismogenic fault is near the SW end of the JF array, in agreement with a prominent geomorphologic feature. The existence of intense local damage on the crustal block with faster larger scale velocity at depth is consistent with common propagation of earthquake ruptures in the area to the NW.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ben-Zion, Y.0000-0002-9602-2014
Ross, Z. E.0000-0002-6343-8400
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Received: 05 December 2016; Revision Received: 02 March 2017; Accepted: 06 March 2017; Published: 07 March 2017. The study was supported by the National Science Foundation (grant EAR-162061) and the U.S. Department of Energy (awards DE-SC0016520 and DE-SC0016527). We thank the Anza-Borrego Desert State Park for permission to collect data on Jackass Flat. The seismic instruments were provided by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech. Data collected are available through the IRIS Data Management Center. 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 by two anonymous referees.
Group:Seismological Laboratory
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0016520
Department of Energy (DOE)DE-SC0016527
Department of Energy (DOE) National Nuclear Security AdministrationUNSPECIFIED
Subject Keywords:Body waves, Earthquake dynamics, Guided waves, Interface waves, Rheology and friction of fault zones, Continental tectonics: strike-slip and transform
Issue or Number:3
Record Number:CaltechAUTHORS:20170913-154346772
Persistent URL:
Official Citation:H. Qiu, Y. Ben-Zion, Z.E. Ross, P.-E. Share, F.L. Vernon; Internal structure of the San Jacinto fault zone at Jackass Flat from data recorded by a dense linear array, Geophysical Journal International, Volume 209, Issue 3, 1 June 2017, Pages 1369–1388,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81427
Deposited By: Tony Diaz
Deposited On:14 Sep 2017 02:33
Last Modified:15 Nov 2021 19:43

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