HR: 10:35h
AN: G42A-02 INVITED     [Abstracts]
TI: SAR Observations and Theoretical Simulations of Interseismic, Coseismic, and Postseismic deformation: Toward a Realistic Mechanical Model of the Earth's Crust
AU: * Fialko, Y
EM: yfialko@ucsd.edu
AF: UCSD, IGPP-0225, La Jolla, CA 92093-0225 United States
AB: Spatially continuous and dense mapping of surface strain allowed by Synthetic Aperture Radar (SAR) reveals details of surface deformation associated with the earthquake cycle that can be used to infer the effective rheology of the Earth's crust, and perhaps the upper mantle. Comprehensive measurements of coseismic deformation (in some instances, in 3-D) due to large shallow earthquakes indicate that the upper crust to the first order is well described by the linearly elastic-brittle behavior. Variations in the effective elastic structure (e.g., the shear modulus) can be quite significant, both in vertical and horizontal dimensions. The vertical variations (e.g., due to layering) cannot be deduced from measurements of surface strain, and must be accounted for using auxiliary information. The lateral variations have a more discernible impact on the deformation field, although there are trade-offs between the rigidity structure and the rupture geometry. I show that such trade-offs may be reduced by combining the coseismic and interseismic geodetic measurements from the same area. The inferred lateral variations in the effective static elastic moduli of the upper crustal rocks are significant, from a factor of 2 contrasts between the damaged rocks within kilometer-wide fault zones and the ambient crustal rocks, to a factor of 3-5 contrasts across large-offset faults such as the San Andreas fault in southern California, presumably due to different lithologies of terrains brought in contact by the fault. The spatial and temporal signatures of postseismic relaxation imaged with interferometric SAR reveal a complex rheologic response of the crust to the coseismically induced stress changes, that appear to involve a variety of mechanisms, including poroelastic relaxation in the upper crust, afterslip on or below the seismic rupture, and perhaps visco-elasto-plastic yielding of the lower crust and upper mantle. The relative contributions of these relaxation mechanisms appear to be different for different events, hindering robust forecasts of the postseismic strain evolution.
UR: http://sioviz.ucsd.edu/~fialko/research4.html
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 1243 Space geodetic surveys
DE: 7215 Earthquake source observations (1240)
DE: 8419 Volcano monitoring (7280)
SC: Geodesy [G]
MN: Fall Meeting 2005