HR: 1400h
AN: G43B-08    [Abstracts]
TI: Space geodetic investigation of the co- and post-seismic deformation due to the 2003 M_w 7.3 Altai earthquake: Implications for the local lithospheric rheology
AU: * Barbot, S D
EM:
AF: Institute of Geophysics and Planetary Physics, 9500 Gilman Dr. 0225, La Jolla, CA 92093, United States
AU: Hamiel, Y
EM: yhamiel@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, 9500 Gilman Dr. 0225, La Jolla, CA 92093, United States
AU: Fialko, Y
EM: yfialko@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, 9500 Gilman Dr. 0225, La Jolla, CA 92093, United States
AB: We use ENVISAT Advanced Synthetic Aperture Radar data and SPOT optical imagery to investigate the co- seismic and post-seismic deformation due to the September 27th 2003, M_w7.3 Altai earthquake, which occurred in the Chuya Basin near the Russia-China-Mongolia border. Based on the SAR and SPOT data, we determined the rupture location and developed a co-seismic slip model for the Altai earthquake. The inferred rupture location is in good agreement with field observations, and the geodetic moment from our slip model is consistent with the seismic moment determined from the tele-seismic data. While the epicentral area of the Altai earthquake is not optimal for radar interferometry (in particular, due to temporal decorrelation), we were able to detect a transient signal over a time period of 3 years following the earthquake. The signal is robust in that it allows us to discriminate among several commonly assumed mechanisms of post-seismic relaxation. We find that the post-earthquake InSAR data do not warrant poro-elastic rebound in the upper crust. The observed deformation also disagrees with linear viscous-elastic relaxation in the upper-mantle or lower-crust. The data can be explained in terms of fault slip in the seismogenic zone, at the margin of areas with high co-seismic slip. Most of the postseismic deformation can be explained in terms of seismic moment release in aftershocks, however, some slip may have occurred aseismically. The observed post-seismic deformation due to the Altai earthquake is qualitatively different from deformation due to other similar-size earthquakes, in particular, the Landers and Hector Mine earthquakes in the Mojave desert, southern California. The observed variations in the deformation pattern may be indicative of different rheologic structure of the continental lithosphere in different tectonically active areas.
DE: 1020 Composition of the continental crust
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1209 Tectonic deformation (6924)
SC: Geodesy [G]
MN: 2007 Joint Assembly