HR: 0800h
AN: S11B-1025    [Abstracts]
TI: Relocation of a Cluster of Earthquakes in the Wabash Valley Seismic Zone
AU: * Eagar, K C
EM: keagar@indiana.edu
AF: Indiana University, Department of Geological Sciences 1001 East 10th Street, Bloomington, IN 47405
AU: Pavlis, G L
EM: pavlis@indiana.edu
AF: Indiana University, Department of Geological Sciences 1001 East 10th Street, Bloomington, IN 47405
AU: Hamburger, M W
EM: hamburg@indiana.edu
AF: Indiana University, Department of Geological Sciences 1001 East 10th Street, Bloomington, IN 47405
AB: In 1995-1996, a regional network of 10 three-component seismometers and a 10 element three-component phased array was deployed in the Wabash River valley of southern Illinois and Indiana. Previous analysis of 83 days detected 232 earthquakes. Nearly 78% of these earthquakes were located near the town of New Harmony, IN and form what we refer to as the New Harmony cluster. We finished processing the remaining 128 days of data and 417 more earthquakes were added to the catalog. The majority of the coherent signals during this deployment were distinguished as quarry blasts, while at most 20% represent earthquakes. Beamforming from the array produced backazimuths and slowness vectors used for initial locations, however accuracy is limited by the low-amplitude, emergent nature of the signal. The geometry of this cluster currently extends 40 km southeast of the array. Since the earthquakes display similarities in phase arrivals, amplitude, and frequency content, we suggest a more closely spaced grouping. Ongoing work continues on a cross-correlation approach to improve initial locations.
DE: 7230 Seismicity and seismotectonics
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2004 AGU Fall Meeting