HR: 0800h
AN: T51D-0767    [Abstracts]
TI: High-resolution Earthquake Location in the New Madrid Seismic Zone
AU: * Dunn, M
EM: mmdunn@memphis.edu
AF: University of Memphis, CERI, 3876 Central Avenue, Suite 1, Memphis, TN 38152,
AU: Horton, S
EM: shorton@memphis.edu
AF: University of Memphis, CERI, 3876 Central Avenue, Suite 1, Memphis, TN 38152,
AU: DeShon, H R
EM: hdeshon@memphis.edu
AF: University of Memphis, CERI, 3876 Central Avenue, Suite 1, Memphis, TN 38152,
AU: Powell, C
EM: capowell@memphis.edu
AF: University of Memphis, CERI, 3876 Central Avenue, Suite 1, Memphis, TN 38152,
AB: We present high-resolution earthquake locations for the New Madrid Seismic Zone (NMSZ) using the double- difference method developed by Waldhauser and Ellsworth (2000). The NMSZ consists of three intersecting faults centered in the central United States and is one of the few places where earthquakes frequently occur away from a major plate boundary. The zone generates approximately 200 earthquakes per year, and double- difference relocation techniques prove well suited for this region because the distance between neighboring events is small and station coverage relatively dense. The initial dataset consists of 1394 earthquakes recorded between 2000 and 2006 by 197 stations. The catalog contains approximately 67,000 P-wave and 54,000 S-wave observations, which yields 480,000 differential times. Waveform cross-correlation of P and S-waves provides an additional 73,000 high-precision differential times. We use the 1D model generated for the NMSZ. One unique characteristic of this model is the high (>3.0) Vp/Vs ratio, which reflects the thick sediment coverage in the region. Tests using synthetic data indicate that this high ratio has little effect on locations. Following relocation, hypocenters align along individual segments of the seismic zone and provide a sharper image of the NMSZ faults. We establish the robustness of these results through the use of synthetic differential times. We will also present initial P-wave and Vp/Vs velocity models derived using the double-difference tomography approach of Zhang and Thurber (2003).
DE: 8180 Tomography (6982, 7270)
DE: 8199 General or miscellaneous
SC: Tectonophysics [T]
MN: 2007 Fall Meeting