HR: 08:30h
AN: G21D-03    [Abstracts]
TI: Evolution of Deformation, Pore Pressure, and Coulomb Stress Following the M9 Sumatra- Andaman Earthquake.
AU: * Masterlark, T
EM: masterlark@geo.ua.edu
AF: The University of Alabama, 202 Bevill Bldg., Tuscaloosa, AL 35487, United States
AU: Hughes, K L
EM: klhughes@bama.ua.edu
AF: The University of Alabama, 202 Bevill Bldg., Tuscaloosa, AL 35487, United States
AB: The M9 Sumatra-Andaman Earthquake of 2004 ruptured the interface of the subducting Indo-Australian plate and overriding Burma microplate. Near-field GPS measurements of the coseismic deformation are on the order of several meters. This deformation induced a devastating tsunami and generated transient stress and pore pressure changes that triggered numerous aftershocks, including the M8.7 Nias earthquake. Finite element models (FEMs) are uniquely capable of simulating the coseismic load and induced evolution of postseismic deformation, pore pressure, and Coulomb stress; while simultaneously honoring the known geologic complexity of the subduction zone. We construct FEMs that simulate deformation of the earthquake for a three-dimensional problem domain partitioned to account for the distribution of material properties of the subducting slab, mantle wedge, forearc, volcanic arc, and backarc. The coseismic slip distribution is estimated from the near-field GPS data via standard inverse methods and FEM-generated Green's functions. Forward models, driven by this slip distribution, predict the evolution of poroelastic and viscoelastic deformation, stress, and pore pressure following the earthquake. Preliminary results suggest poroelastic deformation may be up to several tens-of-centimeters in offshore regions, although predicted poroelastic displacements for near-field GPS sites are generally a few centimeters. Initial pore pressure magnitudes, due to the load of the coseismic slip, exceed 1 MPa in the near- field region. Predicted postseismic pore pressure recovery correlates to the observed spatial and temporal distribution of aftershock swarms, in accord with the poroelastic formulation of Coulomb failure theory. Although the predicted poroelastic displacements are resolvable by GPS measurements in the near-field region, more than a meter of viscoelastic deformation is expected for near-field GPS sites over the next decade.
DE: 0560 Numerical solutions (4255)
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 3260 Inverse theory
DE: 5114 Permeability and porosity
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Geodesy [G]
MN: 2007 Fall Meeting