Numerical Simulation and Discussion on the Mechanism of Postseismic Deformation After Kunlun <i>M</i>_s8.1 Earthquake

Abstract

Abstract On November 14th 2001 an earthquake of magnitude M s 8.1 occurred at the Qinghai‐Xizang Plateau in China. The deformation observed by GPS showed that there were many differences between the deformations of south and north sides of the Kunlun fault. And after a short span of about three months, the deformations at all GPS stations were eastward. In this paper, the postseismic deformation observed by GPS is used as constraints and we analyze the possible mechanism of postseismic deformation after Kunlun earthquake. Firstly, this paper constructs the virtual work equation and theoretically analyzes the effects of heterogeneous, viscoelastic, poroelastic characters on the postseismic deformation. Then this paper uses grid‐search procedure to determine the viscosity for different models. The best‐fitting viscosity of lower crust is 5.0 × 10 17 Pa·s and 9.0 × 10 18 Pa·s for the south and north side of Kunlun fault, respectively. The difference of viscosities brought on the special postseismic deformation. And this difference is not only the result of long‐term geological action but also one of the crucial factors of modern geodynamic environment. On the other hand, the simulation shows that the postseismic deformation after 2001 Kunlun M s 8.1 earthquake is caused not only by the viscoelastic relaxation but also by poroelastic relaxation. So, it is necessary that the viscoelastic relaxation and poroelastic rebound should be combinedly considered when analyzing poseismic deformation.