Parameter Inversion of the 1997 Mani Earthquake from Insar Co‐Seismic Deformation Field Based on Linear Elastic Dislocation Model–I. Uniform Slip Inversion

Abstract

AbstractThe Nov. 8, 1997 Mani (Xizang) Mw7.5 Earthquake is an important event since Synthetic Aperture Radar Interferometry was used for earthquake studies. Peltzer et al. argued that the deformation field indicated the nonlinear elastic response of crust with a ratio of 2 between compressive and tensile elastic moduli. No other similar case appeared in co‐seismic deformation field. Generally, linear elastic theory can give satisfactory explanation to the observation. Considering their excessively simplified fault model and the pure strike‐slip assumption, we deem that nonlinear elasticity explanation is far‐fetched. By using the widely‐used Okada linear elastic dislocation model and the fault location on the surface from satellite observations, removing the zero dip‐slip constraint, we seek best‐fit fault geometry parameters and uniform slip vectors from radar observation based on nonlinear optimization inversion. The result shows that linear elastic model can satisfactorily explain the observation. The maximum depth of the fault reaches 16.5 km at the segment near the east side of Chaoyang Lake. The depth decreases gradually when the fault extending to the east and the west; inverted fault dipping direction and dip‐slip are consistent with field investigation; the maximum strike‐slip component reaches 4.44 m, and the dip‐slip component also reaches its maximum 1.1 m at this segment, which can not be ignored in the inversion; the total seismic moment is 2.08×1020 N·m from inversion, which equals to a Mw7.5 earthquake. The seismic moment is close to the 2.23×1020 N·m of Harvard solution and the 1.8×1020 N·m of Velasco's inversion.