Fault-Plane Determination of the 18 April 2008 Mount Carmel, Illinois, Earthquake by Detecting and Relocating Aftershocks
- Creators
- Yang, Hongfeng
- Zhu, Lupei
- Chu, Risheng
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_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°±11° and dips 81°±7° 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.
Additional Information
© 2009 Seismological Society of America. Manuscript received 11 February 2009. The authors thank editor Ivan G. Wong and two anonymous reviewers for their valuable comments that improved the manuscript greatly. We benefited from discussions with Robert B. Herrmann and John Encarnicion of Saint Louis University. We also thank Abuduwasiti Wulamu of Saint Louis University for helping to visualize 3D relocation results. This work is supported by the National Science Foundation under Grant Number EAR-0609969.Attached Files
Published - Yang2009p6510B_Seismol_Soc_Am.pdf
Supplemental Material - 2009038-esupp_Table1.dat.zip
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Additional details
- Eprint ID
- 16899
- Resolver ID
- CaltechAUTHORS:20091208-111254029
- EAR-0609969
- NSF
- Created
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2009-12-08Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field