HR: 16:45h
AN: U44A-06    [Abstracts]
TI: Structural Setting and Seismicity in the Vicinity of the Great Sumatra-Andaman Islands Earthquake
AU: * Ritzwoller, M H
EM: ritzwoller@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0390 United States
AU: Shapiro, N M
EM: nshaprio@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0390 United States
AU: Engdahl, E R
EM: engdahl@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0390 United States
AU: Levshin, A L
EM: levshin@ciei.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0390 United States
AU: Park, J
EM: jeffrey.park@yale.edu
AF: Department of Geology and Geophysics, Yale University, New Haven, CT 06520-8109 United States
AB: The earthquake of 26 December 2004 was a thrust event that occurred at the interface between the Burma/Andaman Plate and the Indian Plate. We discuss the seismic and thermal structure of the upper mantle in the vicinity of this earthquake revealed by modeling broad-band surface wave dispersion. The upper mantle model is constructed on a 1 deg by 1 deg grid across a broad region centered on the Sumatra-Andaman Islands earthquake. Seismic and thermal parameterizations are used in the Monte-Carlo inversion resulting in both a shear velocity and temperature model of the upper mantle to a depth of about 250 km. Several issues are discussed: (1) the thermal age of the incoming Indian plate, (2) the ability to resolve slabs subducting at the Andaman, Sunda, and Java trenches, (3) the extent and geometry of the subducting plate, (4) thermal anomalies associated with the Andaman Spreading Zone, and (5) the possibility of high temperature (low velocity) anomalies in the supra-slab mantle wedge that may be associated with slow moment release down-dip of the rupture zone. Slow moment release may be responsible for discrepancies between moment release estimated with the gravest normal modes and with long period surface waves. Finally, historical and recent seismicity is presented in the context of the mantle model. Particular attention is paid to the depth extent of seismicity and the correlation of hypocentral locations with images of the subducted slab.
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
DE: 8150 Plate boundary--general (3040)
DE: 8180 Tomography
SC: Union [U]
MN: 2005 Joint Assembly