Hypocentral Relocations of the 2008 Mt. Carmel, Illinois Aftershock Sequence
Abstract
On April 18, 2008, a moderate sized earthquake (Mw 5.2, hypocentral depth of 16 km) occurred near the Indiana-Illinois state border within 3 km of the Mt. Carmel-New Harmony fault at the northern termination of the Wabash Valley Fault System. A total of 257 aftershocks were recorded over the next month by a fourteen-station temporary network deployed by Indiana University and University of Memphis/Center of Earthquake Research and Information (CERI). The number of recorded aftershocks is greater than aftershocks recorded from previous earthquakes in the WVFS of similar magnitude within the last 50 years. The number and density of local stations allowed the generation of precise hypocentral relocations with the combination of waveform cross-correlation and joint hypocentral techniques. The relocated hypocenters indicate a well-defined near-vertical fault plane striking east-west. The fault orientation is consistent with the focal mechanism of the main shock and nearly orthogonal with respect to the trace of the neighboring Mt. Carmel-New Harmony fault. The interpreted ruptured fault orientation suggests the aftershock sequence occurred on a transfer structure at the fault termination. The structure may be related to the change in deformation styles suggested by the transition from the northeast-trending WVFS to the northwest-trending La Salle anticlinorium.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.S51B1421S
- Keywords:
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- 7230 SEISMOLOGY / Seismicity and tectonics;
- 8010 STRUCTURAL GEOLOGY / Fractures and faults