Seismogenic, coseismic and postseismic deformation and stress evolution of the 2008 Wenchuan earthquake: Numerical simulation analysis

Abstract

The 2008 MS 8.0 Wenchuan earthquake occurred in the Longmenshan fault zone, which has complex geological background, strong surface relief, and heterogeneous elastic-viscous structures; however, the seismic risk of the Longmenshan fault zone was underestimated before the Wenchuan earthquake due to the low seismicity and slight surface tectonic deformation. We established an elastic-viscous finite element model from the perspective of numerical simulation, taking multiple factors into consideration, such as initial topography, gravity, tectonic loading, and viscoelastic relaxation of the middle and lower crusts and the upper mantle. The effects of the mentioned factors on the dynamic process of seismogenic and coseismic deformations of the 2008 Wenchuan earthquake as well as the postseismic deformation in 150 years were analyzed. We quantitively studied the coseismic and postseismic deformations of the Yingxiu-Beichuan fault zone, and summerized the characteristics of stress accumulation, release, and adjustment in both the elastic and viscoelastic layers. The simulation results of the surface coseismic and postseismic displacements showed a good agreement with the geodetic data, and the aftershock distribution of the Wenchuan earthquake was explained in mechanics. The changes in preseismic, coseismic, and postseismic stress were calculated to analyze the dynamic cause of the Wenchuan earthquake and the influence on the seismic risk of surrounding areas.

Keywords

• wenchuan earthquake
• viscoelasticity
• stress adjustment
• postseismic deformation
• finite element model