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Source properties of earthquakes near the Salton Sea triggered by the 16 October 1999 M 7.1 Hector Mine, California, earthquake

Hough, Susan E. and Kanamori, Hiroo (2002) Source properties of earthquakes near the Salton Sea triggered by the 16 October 1999 M 7.1 Hector Mine, California, earthquake. Bulletin of the Seismological Society of America, 92 (4). pp. 1281-1289. ISSN 0037-1106. doi:10.1785/0120000910.

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We analyze the source properties of a sequence of triggered earthquakes that occurred near the Salton Sea in southern California in the immediate aftermath of the M 7.1 Hector Mine earthquake of 16 October 1999. The sequence produced a number of early events that were not initially located by the regional network, including two moderate earthquakes: the first within 30 sec of the P-wave arrival and a second approximately 10 minutes after the mainshock. We use available amplitude and waveform data from these events to estimate magnitudes to be approximately 4.7 and 4.4, respectively, and to obtain crude estimates of their locations. The sequence of small events following the initial M 4.7 earthquake is clustered and suggestive of a local aftershock sequence. Using both broadband TriNet data and analog data from the Southern California Seismic Network (SCSN), we also investigate the spectral characteristics of the M 4.4 event and other triggered earthquakes using empirical Green's function (EGF) analysis. We find that the source spectra of the events are consistent with expectations for tectonic (brittle shear failure) earthquakes, and infer stress drop values of 0.1 to 6 MPa for six M 2.1 to M 4.4 events. The estimated stress drop values are within the range observed for tectonic earthquakes elsewhere. They are relatively low compared to typically observed stress drop values, which is consistent with expectations for faulting in an extensional, high heat flow regime. The results therefore suggest that, at least in this case, triggered earthquakes are associated with a brittle shear failure mechanism. This further suggests that triggered earthquakes may tend to occur in geothermal–volcanic regions because shear failure occurs at, and can be triggered by, relatively low stresses in extensional regimes.

Item Type:Article
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URLURL TypeDescription
Hough, Susan E.0000-0002-5980-2986
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2002 Seismological Society of America. Manuscript received 18 October 2000. I thank Joan Gomberg, Paul Bodin, Rachel Abercrombie, Victoria Langenheim, Ned Field, Ewa Glowacka, and an anonymous reviewer for comments and discussions that greatly improved this manuscript. This research was supported by the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement Number EAR-8920136 and USGS Cooperative Agreements Number 14-08-0001-A0899 and 1434-HQ-97AG01718. The SCEC Contribution Number for this paper is 575.
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
NSF Cooperative AgreementEAR-8920136
USGS Cooperative Agreement14-08-0001-A0899
USGS Cooperative Agreement1434-HQ-97AG01718
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center575
Issue or Number:4
Record Number:CaltechAUTHORS:20140115-154238987
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43394
Deposited By: Tony Diaz
Deposited On:30 Jan 2014 18:02
Last Modified:10 Nov 2021 16:37

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