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Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake

dc.contributor.authorYao, Dongdong
dc.contributor.authorHuang, Yihe
dc.contributor.authorPeng, Zhigang
dc.contributor.authorCastro, Ra�l R.
dc.date.accessioned2020-07-02T20:34:30Z
dc.date.availableWITHHELD_12_MONTHS
dc.date.available2020-07-02T20:34:30Z
dc.date.issued2020-06
dc.identifier.citationYao, Dongdong; Huang, Yihe; Peng, Zhigang; Castro, Ra�l R. (2020). "Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake." Journal of Geophysical Research: Solid Earth 125(6): n/a-n/a.
dc.identifier.issn2169-9313
dc.identifier.issn2169-9356
dc.identifier.urihttps://hdl.handle.net/2027.42/155988
dc.description.abstractForeshocks can provide valuable information about possible nucleation process of a mainshock. However, their physical mechanisms are still under debate. In this study, we present a comprehensive analysis of the earthquake sequence preceding the 2010 Mw7.2 El Mayor‐Cucapah mainshock, including waveform detection of missing smaller events, relative relocation, and source parameter analysis. Based on a template matching method, we find a tenfold increase in the number of earthquakes than reported in the Southern California Seismic Network catalog. The entire sequence exhibits nearly continuous episodes of foreshocks that can be loosely separated into two active clusters. Relocated foreshocks show several seismicity streaks at depth, with a consistently active cluster at depths between 14 and 16 km where the mainshock was nucleated. Stress drop measurements from a spectral ratio approach based on empirical Green’s functions show a range between 3.8 and 41.7 MPa with a median of 13.0 MPa and no clear temporal variations. The relocation results, together with the source patches estimated from earthquake corner frequencies, revealed a migration front toward the mainshock hypocenter within last 8 hr and a chain of active burst immediately 6 min prior to the mainshock. Our results support combined effects of aseismic slip and cascading failure on the evolution of foreshocks.Plain Language SummaryThe 2010 Mw7.2 El Mayor‐Cucapah (EMC) earthquake was preceded by a prominent sequence of foreshocks starting ~21 days before the mainshock. Several methods based on the similarities of waveforms are applied to obtain spatiotemporal evolution of foreshocks. Ten times more events are found from a template matching method when compared to the SCSN catalog. The refined relative locations reveal two main active clusters in time, as well as two spatial patches with a shallower one to the north of the mainshock epicenter. The depth distribution indicates several linear lines of seismicity, with a consistently active cluster at depths of 14–16 km where mainshock started. An active cluster of foreshocks occurred in the last 6 min. They likely altered the stress state near the hypocenter and ultimately triggered the mainshock. Our analysis indicates that both aseismic slip and cascade triggering processes occurred and contributed to the eventual triggering of the EMC mainshock.Key PointsA waveform matching technique leads to tenfold increase in the number of foreshocks when compared with the SCSN catalogWe resolve the corner frequency of 20 foreshocks using the detected events as empirical Green’s functionsThe relocated catalog and estimated source patches reveal effects of both aseismic slip and cascading stress transfer
dc.publisherCambridge University Press
dc.publisherWiley Periodicals, Inc.
dc.subject.otherforeshock and mainshock nucleation
dc.subject.otherearthquake detection/relocation
dc.subject.otherstress drop
dc.subject.otherEl Mayor‐Cucapah earthquake
dc.titleDetailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake
dc.typeArticle
dc.rights.robotsIndexNoFollow
dc.subject.hlbsecondlevelGeological Sciences
dc.subject.hlbtoplevelScience
dc.description.peerreviewedPeer Reviewed
dc.description.bitstreamurlhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/1/jgrb54188.pdf
dc.description.bitstreamurlhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/2/jgrb54188_am.pdf
dc.identifier.doi10.1029/2019JB019076
dc.identifier.sourceJournal of Geophysical Research: Solid Earth
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dc.owningcollnameInterdisciplinary and Peer-Reviewed


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