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The 1999 M_w 7.1 Hector Mine, California, Earthquake Sequence: Complex Conjugate Strike-Slip Faulting

Hauksson, Egill and Jones, Lucile M. and Hutton, Kate (2002) The 1999 M_w 7.1 Hector Mine, California, Earthquake Sequence: Complex Conjugate Strike-Slip Faulting. Bulletin of the Seismological Society of America, 92 (4). pp. 1154-1170. ISSN 0037-1106.

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The 1999 M_w 7.1 Hector Mine mainshock showed right-lateral strike-slip faulting, with an initial strike of N6°W and vertical dip. The mainshock was preceded within 20 hours by 18 recorded foreshocks of 1.5 ≤ M ≤ 3.8 within a few kilometers distance of the mainshock hypocenter. The aftershocks delineate how the Hector Mine earthquake ruptured with strike N6°W to the south for a distance of 15 km, and possibly to the north for a distance of several kilometers. The two largest aftershocks of M 5.9 and M 5.7 occurred near the north and south ends of the first mainshock rupture segment. The second segment of rupture, starting 15 km to the south away from the mainshock hypocenter, delineated by strike-slip and thrust-faulting aftershocks, extends 10 km farther away with a strike of S140°E along the Bullion fault. The aftershocks also outline an unusual third rupture segment, extending from about 5 km south of the hypocenter with a strike of N30°W to N35°W for a distance of 20 km. Approximately 10 to 25 km farther to the north and west of the mainshock epicenter, several clusters form a complex aftershock distribution. Three-dimensional Vp and Vp/Vs models of the region exhibit only small regional changes, as is typical for the Mojave region. Nonetheless, the mainshock rupture started within a region of rapidly varying Vp, and at least three regions of low Vp/Vs are imaged within the aftershock zone. The rate of decay for the Hector Mine earthquake sequence has been slightly above the mean for both p-values and b-values in southern California. The focal mechanisms of the aftershocks and the state of stress are consistent with strike-slip faulting, including a component of normal faulting most prominent to the north. The orientation of the regional maximum horizontal stress, the variation in orientation of the mainshock fault segments by 30°, and scattered distribution of aftershocks suggest that the mainshock and aftershock deformation field exhibit volumetric shear deformation accommodated by complex conjugate sets of strike-slip faults.

Item Type:Article
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URLURL TypeDescription
Hauksson, Egill0000-0002-6834-5051
Jones, Lucile M.0000-0002-2690-3051
Additional Information:© 2002 Seismological Society of America. Manuscript received 10 December 2000. Most figures were done using GMT (Wessel and Smith, 1991) and Zmap (Wiemer, 2000). This research was supported by U.S. Geological Survey Grant Numbers 99HQGR0039 and 01HQGR038 to Caltech and grants from the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement Number EAR-8920136 and USGS Cooperative Agreement Numbers 14-08-0001-A0899 and 1434-HQ-97AG01718. SCEC Contribution Number 553. Contribution Number 8748, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena.
Group:Seismological Laboratory, Division of Geological and Planetary Sciences
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Southern California Earthquake Center (SCEC)UNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)553
Caltech Division of Geological and Planetary Sciences8748
Issue or Number:4
Record Number:CaltechAUTHORS:20130228-074444230
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Official Citation:Egill Hauksson, Lucile M. Jones, and Kate Hutton The 1999 Mw 7.1 Hector Mine, California, Earthquake Sequence: Complex Conjugate Strike-Slip Faulting Bulletin of the Seismological Society of America, May 2002, v. 92, p. 1154-1170, doi:10.1785/0120000920
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37187
Deposited By: Ruth Sustaita
Deposited On:28 Feb 2013 16:20
Last Modified:24 Feb 2020 10:30

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