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Fault-plane determination of the 18 April 2008 Mount Carmel, Illinois, earthquake by detecting and relocating aftershocks

Hongfeng Yang, Lupei Zhu and Risheng Chu
Fault-plane determination of the 18 April 2008 Mount Carmel, Illinois, earthquake by detecting and relocating aftershocks
Bulletin of the Seismological Society of America (December 2009) 99 (6): 3413-3420

Abstract

We developed a sliding-window cross-correlation (SCC) detection technique and applied the technique to continuous waveforms recorded by the Cooperative New Madrid Seismic Network stations following the 18 April 2008 Illinois earthquake. The technique detected more than 120 aftershocks down to M (sub L) 1.0 in the 2 week time window following the mainshock, which is three times more than the number of aftershocks reported by the seismic network. Most aftershocks happened within 24 hrs of the mainshock. We then relocated all events by the double-difference relocation algorithm. Accurate P- and S-wave differential arrival times between events were obtained by waveform cross correlation. After relocation, we used the L1 norm to fit all located events by a plane to determine the mainshock fault plane. The best-fit plane has a strike of 292 degrees + or -11 degrees and dips 81 degrees + or -7 degrees to the northeast. This plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks. By combining the aftershock locations and focal mechanism solutions, we conclude that the 18 April earthquake occurred on a nearly vertical left-lateral strike-slip fault orienting in the west-northwest-east-southeast direction. The fault coincides with the proposed left-stepping Divide accommodation zone in the La Salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the Midcontinent.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 99
Serial Issue: 6
Title: Fault-plane determination of the 18 April 2008 Mount Carmel, Illinois, earthquake by detecting and relocating aftershocks
Affiliation: Saint Louis University, Department of Earth and Atmospheric Sciences, Saint Louis, MO, United States
Pages: 3413-3420
Published: 200912
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 38
Accession Number: 2010-012564
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N38°30'00" - N38°30'00", W88°00'00" - W88°00'00"
Secondary Affiliation: California Institute of Technology, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201008
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