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Crustal structure and seismicity distribution adjacent to the Pacific and North American plate boundary in southern California

Hauksson, Egill (2000) Crustal structure and seismicity distribution adjacent to the Pacific and North American plate boundary in southern California. Journal of Geophysical Research B, 105 (B6). pp. 13875-13903. ISSN 0148-0227. doi:10.1029/2000JB900016.

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New three-dimensional (3-D) V_P and V_P/V_S models are determined for southern California using P and S-P travel times from local earthquakes and controlled sources. These models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the Pacific-North America plate boundary. The models extend from the U.S.-Mexico border in the south to the southernmost Coast Ranges and Sierra Nevada in the north and have a 15-km horizontal grid spacing and an average vertical grid spacing of 4 km, down to 22 km depth. The heterogeneity of the crustal structure as imaged by V_P and V_P/V_S models is larger within the Pacific plate than the North American plate. Similarly, the relocated seismicity deepens and shows more complex 3-D distribution in areas of the Pacific plate exhibiting compressional tectonics. The models reflect mapped changes in the lithology across major geological terranes such as the Mojave Desert, the Peninsular Ranges, and the Transverse Ranges. The interface between the shallow Mono of the Continental Borderland and the deep Moho of onshore California forms a broad zone to the north beneath the western Transverse Ranges, Ventura basin, and the Los Angeles basin and a narrow zone to the south, along the Peninsular Ranges. The near-surface increase in velocity, from the surface to up to 8 km depth, is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins. At midcrustal depths a rapid increase in V_P is imaged beneath the sediments of the large sedimentary basins, while beneath the adjacent mountain ranges the increase is small or absent.

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Hauksson, Egill0000-0002-6834-5051
Additional Information:© 2000 American Geophysical Union. Manuscript Accepted: 20 December 1999; Manuscript Received: 15 June 1999. M. Oskin, J. Hardebeck, L. Jones, and two JGR reviewers, W. Lutter and N. Godfrey, provided comprehensive reviews. This research was supported by U.S. Geological Survey grants 1434-HQ-97-GR-02038 and 99HQGR0039 to Caltech SCEC is funded by NSF Cooperative Agreement EAR-8920136 and USGS Cooperative Agreement 14-08-0001-A0899 and 1434-HQ-97AG01718. Electronic version of the velocity models and the relocated catalog are available from the author or from the Southern California Earthquake Center, Data Center, anonymous FTP at scec.scecdc.orign /pub/hauksson. All maps and cross sections were made using GMT (Generic Mapping Tools) software [Wessel and Smith, 1991]. Contribution 8623, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena. Southern California Earthquake Center contribution 493.
Group:Seismological Laboratory
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Caltech Division of Geological and Planetary Sciences8623
Southern California Earthquake Center (SCEC)493
Issue or Number:B6
Record Number:CaltechAUTHORS:20130514-103432435
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Official Citation:Hauksson, E. (2000), Crustal structure and seismicity distribution adjacent to the Pacific and North America plate boundary in southern California, J. Geophys. Res., 105(B6), 13875–13903, doi:10.1029/2000JB900016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38492
Deposited By: Jason Perez
Deposited On:14 May 2013 18:21
Last Modified:09 Nov 2021 23:37

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