Inversion of post-seismic GPS data for effective viscosity of Wenchuan region

Combing with the after-slip model, the viscoelastic relaxation model and the elastic block model, this paper estimates the effective viscosity of middle to lower crust by fitting the observed GPS velocity in Wenchuan region in the period of 2009—2011. The results indicate that the effective viscosity of middle to lower crust in Wenchuan region varies largely for the two sides of Longmenshan fault zone, which impacts the kinematics’patterns of the crust in the study region. The effective viscosity of lower crust is about 7×10¹⁹ Pa·s to the western side of Longmenshan fault except the Minjiang block which contains a slightly stronger middle to lower crust; the effective viscosity is about 7×10²² Pa·s to the eastern side of Longmenshan fault, showing a strong rigid motion characteristics. In addition, the after-slip effect is notable because of the existing coseismic rupture surface.