HR: 10:20h
AN: G12A-01    [Abstracts]
TI: Thin-plate modeling of interseismic deformation, application to the observed asymmetric deformation across the Altyn Tagh fault zone
AU: * Cattin, R
EM: cattin@geologie.ens.fr
AF: Ecole Normale Superieure Laboratoire de Geologie, 24, rue Lhomond, Paris, 75005, France
AU: Jolivet, R
EM: romain.jolivet@wanadoo.fr
AF: Ecole Normale Superieure Laboratoire de Geologie, 24, rue Lhomond, Paris, 75005, France
AU: Chamot-Rooke, N
EM: rooke@geologie.ens.fr
AF: Ecole Normale Superieure Laboratoire de Geologie, 24, rue Lhomond, Paris, 75005, France
AU: Lasserre, C
EM: lasserre@geologie.ens.fr
AF: Ecole Normale Superieure Laboratoire de Geologie, 24, rue Lhomond, Paris, 75005, France
AU: Peltzer, G
EM: peltzer@ess.ucla.edu
AF: Department of Earth and Space Sciences University of California, Los Angeles, 595 Charles Young Drive East, Box 951567, Los Angeles, CA 90095-1567, United States
AB: Geodetic measurements of interseismic velocities are key data for assessing seismic hazard and plate motion in actives fault zone. Creeping dislocations in a homogeneous elastic half-space are commonly used to model these deformations. However it would be more realistic to replace that half-space by elatic plates with finite thickness and rigidity variations. Here, we propose a new modeling approach, which includes a thin-plate model sheared at its base by opposite velocities on both sides of a burried creeping zone. We compare both models for vertical strike-slip fault. Our results suggest that the use of a half-space model to interpret interseismic velocity field leads to underestimate the fault locking depth or to overestimate its slip rate if the far-field velocity is neither available nor well- constrained. Next we apply these two approaches to interpret InSAR data across the Altyn Tagh fault system near longitude 94°E, which shows a significant asymmetry of interseismic velocity. Our results suggest a locking depth of 7- 9 km and a present-day geodetic slip rate of 8-10 mm/yr. We interpret the asymmetric pattern as the joint effect of a rigidity decrease from the Tarim basin north of the fault to the Qaidam basin south of it and of a 5-7 km southward offset of strain concentration from the quaternary active fault. This suggests that the rigidity contrast as well as most of the strain accumulation at depth occurs on the southern geological fault.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 7218 Lithosphere (1236)
DE: 8111 Continental tectonics: strike-slip and transform
SC: Geodesy [G]
MN: 2007 Fall Meeting