Study On Rupture Dynamics Of Three-dimensional Non-planar Fault

The issue of earthquake dynamics, especial for the three-dimensional sponta-neous dynamic rupture of fault with complex geometry, is a hot topic in seismol-ogy. There is no analytic solution for this problem, only relying on simulations with numerical methods. Due to its efficiency and accuracy comparing to oth-ers numerical methods, the finite-difference method (FDM) has become a very common method in the dynamic rupture simulation of earthquake, and has been widely used in earthquake source research and real earthquake modeling.Based upon Cartesian coordinates, the traditional FDM needs to construct orthogonal grids. It cannot be implemented to model dynamic rupture on fault with complex geometry. Although some improvements have been made by previ-ous authors, it is still a long way to common implementation. The problem can be well solved by curvilinear grids, which can be constructed along the irregular interfaces. The curved grid finite-difference method (CG-FDM) has been vali-dated that it can model seismic wave propagation in heterogeneous media with irregular free surface. In this work, we implement the CG-FDM to solve the dy-namic rupture problem. While keeping the advantages of conventional FDM, that is, computational efficiency and easy implementation, CG-FDM also is flexible in modeling the complex fault by using general curvilinear girds, and thus is able to model the rupture dynamics of a fault with complex geometry, such as oblique dipping fault, non-planar fault, fault with step-over, even if irregular topography exists.The discontinuity of fault is represented by split-node in this method. The curvilinear grids is constructed along the irregular fault plane and free surface. With new defined physical variables on split nodes, the elastodynamic equations can be written in form of traction that given by the friction law. For the interjec- tion between fault plane and free surface, we adopt a specific physical condition to make the intersecting point obeying both the laws of faulting and free surface to get the stable simulation.To validate the accuracy of this method, we model spontaneous rupture of some benchmarks provided by South California Earthquake Center, and compare the results with that derived by other numerical methods. After the validations, we simulate rupture on faults with complex geometries and analysis some phe-nomena of earthquake dynamics. At the last, we run the modeling of spontaneous rupture of Wenchuan earthquake, with varying strike and dipping angles and mod-eling parameters are chosen based on field research. Our study reveals that the fault’s geometry of Wenchuan earthquake play an important role on determining the final slipping pattern on fault surface. The simple planar fault and equivalent planar fault cannot give the reasonable distribution of slip on fault surface.Summarily, the method we introducing can model dynamic rupture on3D fault with complex geometry. With enough computing resource, we can model physical-based high-frequency seismic wave from the beginning of rupture dynam-ics, providing scientific foundation for seismic prevention and hazard mitigation.