Study on the influence of local mountainous topography to fault dynamic rupture

In this study, the curved grid finite-difference method was implemented to investigate the effect of local irregular topography on the dynamic rupture process of a vertical strike-slip fault and the resultant strong ground motions. The rupture propagation and ground motions were simulated with different irregular topography in a three-dimensional homogeneous half-space. Our results show that the scale of ridge topography including its height and bottom extension size has great impact on the dynamic rupture process, and then will affect the distribution of ground motions. The mountainous topography will obstruct the generation of super-shear induced by free surface when it is located near the subshear-to-supershear transition position on free surface. Generally, for the faults with a certain buried depth, with the same size of topography bottom extension, the higher the mountain height is, the stronger prevention it has on the generation of super-shear. In addition, when the mountain height is fixed, the larger extension of mountain bottom size has more obstacles to the generation of the super-shear induced by free surface. The variation of fault rupture process will make different distribution of ground motions. Furthermore, the response of dynamic rupture process and the corresponding ground motion to the change of initial shear stress outside the nucleation area was discussed. Our result shows that with the high initial shear stress, the super-shear induced by high stress drop also plays an important role in dynamic rupture and distribution of the resultant ground motion.