Numerical simulation of coseismic and postseismic deformation through a node-splitting algorithm: A case study of the Wenchuan earthquake

Abstract

The coseismic and postseismic effects are crucial elements in analyzing fault interactions and the regional seismic risk. In this paper, we developed a three-dimensional viscoelastic finite element code to simulate the coseismic and postseismic deformation. We calculated the coseismic and postseismic deformations caused by the strike-slip fault with a conceptual model, and compared the results with the analytic and semi-analytic solutions so as to verify the reliability of the code. Meanwhile, we also analyzed the influence of different parameters on the coseismic and postseismic deformation, uncovering a significant effect of the earth's lateral heterogeneity on the coseismic displacement. And the viscosity of the middle-lower crust and upper mantle plays a major role in controlling the postseismic displacement. At last, we used the three-dimensional viscoelastic model to calculate the changes of the coseismic and postseismic Coulomb stress caused by the 2008 MW7.9 Wenchuan earthquake, and analyzed the subsequent effect on the 2013 MW6.6 Lushan earthquake and the 2017 MW6.5 Jiuzhaigou earthquake. The calculation results show that the Coulomb stress changes caused by the Wenchuan earthquake is positive near the hypocenters of the Lushan earthquake (0.013 MPa) and the Jiuzhaigou earthquake (0.009 MPa), indicating the Wenchuan earthquake might have triggered both the Lushan earthquake and Jiuzhaigou earthquake.

Keywords

• earthquake dislocation
• postseismic deformation
• three-dimensional viscoelasticity
• coulomb stress
• wenchuan earthquake