HR: 09:45h
AN: U21C-07    [Abstracts]
TI: Implications of the Postseismic Displacement Field Generated by the 26 December 2004 and 28 March 2005 Earthquakes, as Measured by CGPS
AU: Banerjee, P
EM: parameshb@hotmail.com
AF: Wadia Institute of Himalayan Geology, 33 GMS Road, Dehra Dun, 248001 India
AU: * Pollitz, F F
EM: fpollitz@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025 United States
AU: Burgmann, R
EM: burgmann@seismo.berkeley.edu
AF: Department of Earth and Planetary Science and Berkeley Seismological Laboratory, University of California, Berkeley, CA 94720 United States
AB: The Mw=9.2 26 December 2004 Sumatra-Andaman and M=8.7 28 March 2005 Nias earthquakes, which collectively ruptured approximately 1800 km of the Andaman and Sunda subduction zones, are expected to be followed by vigorous viscoelastic relaxation involving the asthenosphere and underlying mantle. Both afterslip and viscoelastic relaxation may contribute to the postseismic displacement field. Our study explores the latter process using models of oceanic lithosphere and mantle rheology on a self-gravitating, compressible Earth. We present new coseismic slip models of both earthquakes based on compilations of continuous and campaign GPS data from four different regional networks, and we implement them as source models for coseismic and time-dependent postseismic deformation fields. For simple layered viscoelastic models which include a low-viscosity asthenosphere, we predict substantial postseismic effects over a region several 100s of km wide surrounding the eastern Indian Ocean. We compare observed GPS time series from ten regional sites (mostly in Thailand and Indonesia), beginning in December 2004, with synthetic time series that include the coseismic and postseismic effects of the 26 December 2004 and 28 March 2005 earthquakes. A viscosity structure involving a bi-viscous (Burgers body) rheology in the asthenosphere explains the pattern and amplitude of postseismic offsets remarkably well.
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Union [U]
MN: Fall Meeting 2005