The numerical simulation and discussion on mechanism of postseismic deformation after Kunlun Ms 8.1 earthquake
昆仑山Ms 8.1级地震震后变形场数值模拟与成因机理探讨

On November 14th 2001 an earthquake with magnitude of Ms 8.1 occurred at the Qinghai-Xizang Plateau in China. The deformation observed by GPS shows that there are 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 are 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 viscosities of lower crust is 5.0×1017Pa·s and 9.0×1018Pa·s for the south and north sides 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 Ms8.1 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 be combinedly considered during process of analysis of postseismic deformation.