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A three-dimensional crustal seismic velocity model for southern California from a composite event method

Lin, Guoqing and Shearer, Peter M. and Hauksson, Egill and Thurber, Clifford H. (2007) A three-dimensional crustal seismic velocity model for southern California from a composite event method. Journal of Geophysical Research B, 112 (B11). Art. No. B11306. ISSN 0148-0227. doi:10.1029/2007JB004977.

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We present a new crustal seismic velocity model for southern California derived from P and S arrival times from local earthquakes and explosions. To reduce the volume of data and ensure a more uniform source distribution, we compute "composite event" picks for 2597 distributed master events that include pick information for other events within spheres of 2 km radius. The approach reduces random picking error and maximizes the number of S wave picks. To constrain absolute event locations and shallow velocity structure, we also use times from controlled sources, including both refraction shots and quarries. We implement the SIMULPS tomography algorithm to obtain three-dimensional (3-D) V_p and V_p/V_s structure and hypocenter locations of the composite events. Our new velocity model in general agrees with previous studies, resolving low-velocity features at shallow depths in the basins and some high-velocity features in the midcrust. Using our velocity model and 3-D ray tracing, we relocate about 450,000 earthquakes from 1981 to 2005. We observe a weak correlation between seismic velocities and earthquake occurrence, with shallow earthquakes mostly occurring in high P velocity regions and midcrustal earthquakes occurring in low P velocity regions. In addition, most seismicity occurs in regions with relatively low V_p/V_s ratios, although aftershock sequences following large earthquakes are often an exception to this pattern.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Shearer, Peter M.0000-0002-2992-7630
Hauksson, Egill0000-0002-6834-5051
Additional Information:© 2007 by the American Geophysical Union. Received 6 February 2007; revised 10 July 2007; accepted 14 August 2007; published 16 November 2007. All maps and cross sections in this article were made using the GMT mapping tools. We thank Paul Wessel and Walter Smith for developing and supporting GMT. We also thank the anonymous Associate Editor and the reviewer Toshiro Tanimoto for their detailed and constructive reviews. Funding for this research was provided by NEHRP/USGS grant 03HQPA0001 and the Southern California Earthquake Center, which is funded by NSF Cooperative Agreement EAR-0106924 and USGS Cooperative Agreement 02HQAG0008. Research is also supported in part by the U.S. Geological Survey, Department of the Interior, under USGS awards 06HQGR0055 and 07HQGR0050 to the University of Wisconsin-Madison. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. This is SCEC contribution 1050.
Group:Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:composite event; tomography; southern California
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)1050
Issue or Number:B11
Record Number:CaltechAUTHORS:20130304-094912894
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Official Citation:Lin, G., P. M. Shearer, E. Hauksson, and C. H. Thurber (2007), A three-dimensional crustal seismic velocity model for southern California from a composite event method, J. Geophys. Res., 112, B11306, doi:10.1029/2007JB004977
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37268
Deposited By: Tony Diaz
Deposited On:04 Mar 2013 23:49
Last Modified:09 Nov 2021 23:27

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