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Spatial Separation of Large Earthquakes, Aftershocks, and Background Seismicity: Analysis of Interseismic and Coseismic Seismicity Patterns in Southern California

Hauksson, Egill (2010) Spatial Separation of Large Earthquakes, Aftershocks, and Background Seismicity: Analysis of Interseismic and Coseismic Seismicity Patterns in Southern California. Pure and Applied Geophysics, 167 (8-9). pp. 979-997. ISSN 0033-4553. doi:10.1007/s00024-010-0083-3.

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We associate waveform-relocated background seismicity and aftershocks with the 3-D shapes of late Quaternary fault zones in southern California. Major earthquakes that can slip more than several meters, aftershocks, and near-fault background seismicity mostly rupture different surfaces within these fault zones. Major earthquakes rupture along the mapped traces of the late Quaternary faults, called the principal slip zones (PSZs). Aftershocks occur either on or in the immediate vicinity of the PSZs, typically within zones that are ±2-km wide. In contrast, the near-fault background seismicity is mostly accommodated on a secondary heterogeneous network of small slip surfaces, and forms spatially decaying distributions extending out to distances of ±10 km from the PSZs. We call the regions where the enhanced rate of background seismicity occurs, the seismic damage zones. One possible explanation for the presence of the seismic damage zones and associated seismicity is that the damage develops as faults accommodate bends and geometrical irregularities in the PSZs. The seismic damage zones mature and reach their finite width early in the history of a fault, during the first few kilometers of cumulative offset. Alternatively, the similarity in width of seismic damage zones suggests that most fault zones are of almost equal strength, although the amount of cumulative offset varies widely. It may also depend on the strength of the fault zone, the time since the last major earthquake as well as other parameters. In addition, the seismic productivity appears to be influenced by the crustal structure and heat flow, with more extensive fault networks in regions of thin crust and high heat flow.

Item Type:Article
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URLURL TypeDescription DOIArticle
Hauksson, Egill0000-0002-6834-5051
Additional Information:© 2010 Birkhäuser/Springer Basel AG. Received August 5, 2008, revised March 11, 2009, accepted May 24, 2009, Published online March 18, 2010. This research was supported by the US Geological Survey Grant 08HQGR0030 to Caltech, and by the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement EAR-0529922 and USGS Cooperative Agreement 07HQAG0008. We thank L. Jones and P. Shearer for feedback and discussions; and PAGEOPH reviewers and editors for detailed comments. Most figures were done using GMT (WESSEL and SMITH 1998). We thank A. Plesch for doing the distance measurements. SCEC contribution number 1214. Contribution number 10,007, Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena.
Group:Seismological Laboratory
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:Seismicity; California; faults; aftershocks; interseismic seismicity; fault damage zones; San Andreas fault system; evolution of fault zones; earthquake interaction
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)1214
Caltech Seismological Laboratory, Division of Geological and Planetary Sciences10,007
Issue or Number:8-9
Record Number:CaltechAUTHORS:20100913-111429257
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19906
Deposited By: Tony Diaz
Deposited On:16 Sep 2010 21:26
Last Modified:08 Nov 2021 23:56

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