Effects of large historical earthquakes, viscous relaxation, and tectonic loading on the 2008 Wenchuan earthquake

Abstract

The 2008 Wenchuan earthquake (M7.9) occurred on the Longmenshan Fault in Sichuan, China. Both the seismicity and slip rate of the fault are lower than those of other faults in the region. By incorporating large earthquakes in the region during the past 222 years into our investigation, the effects of historical earthquakes, viscous relaxation, and tectonic loading on the Wenchuan earthquake were studied, using a quasi-static, finite element model. In this model, we first simulated an initial stress field constrained by fault slip rates obtained by GPS and geologic observations in the region. We then simulated earthquakes by fault softening. The results show that tectonic loading has the most significant effect on the Longmenshan Fault, whereas viscous relaxation of the lower crust and upper mantle has the least effect. The effects of the historical earthquakes are variable; some promote the earthquake potential and others retard the earthquake potential. © 2012. American Geophysical Union. All Rights Reserved.