Numerical Simulation Of Earthquakes On The Haiyuan Fault

With the exploration of active faults and the study of the paleoseismic event in the Haiyuan fault zone,seismic hazard in the area has attracted the attention of many scholars.By the strong ground motion simulation of historical lager earthquakes and scenario earthquake on the active faults,we can evaluate the seismic hazard scientifically.In recent decades,with the development of rupture dynamics,the simulation of spontaneous rupture process based on the physics can provide a reasonable source model for strong ground motion.In this paper,we apply curve-grid mesh finite difference method to simulate the spontaneous rupture process of earthquakes.Based on the results of the dynamic rupture,we simulate the strong ground motion by the curve-grid finite difference method.The Haiyuan fault zone includes the Jinqianghe fault in the western segment,the Maomaoshan-Laohushan fault in the middle segment,and the narrow Haiyuan fault in the eastern segment.The 16 December 1920 Ms 8.5 Haiyuan,which occurred on the narrow Haiyuan fault,was one of the rare devastating earthquakes in modern China.The surface rupture of the 1920 Haiyuan earthquake reached nearly 237 km with 10-11 m maximum sinistral strike-slip dislocation,and its maximum intensity reached XII.The fault zone is composed of 11 sub-faults with different scales.Pull-apart basins with a width of 1?3 km distributed between the sub-faults.In this paper,three geometric models are set to approximate the seismogenic fault of the Haiyuan earthquake by the surface rupture information.Considering that the instrument epicenter and the macro-seismic of the Haiyuan earthquake are different,we set two kinds of source locations at the same time.We analyze the rupture model for the Haiyuan earthquake for each source location with three geometric fault model.We compare the the surface slip distributions for five models with the investigation to select a better one.It is noticeable that the source location has little effect on the distribution of surface slip.Therefore,we simulate the strong ground motion based on the source models with different source location for further constraining the source location.Because the characteristics between the theoretical intensity and actual intensity distribution are similar,our source model is reasonable.In addition,we study the scenario earthquake on the "Tianzhu seismic gap",which is composed of the Jinqianghe fault,the Maomaoshan-Laohushan fault.First,we analyze the influence of the stress magnitude,stress direction and friction parameters on the rupture propagation in the 1888 Jingtai earthquake on the Laohushan fault zone.Then,we simulated the spontaneous rupture process of the Laohushan fault and the Jinqianghe-Maomao fault with different source locations.Besides,we analyze the theoretical intensity distribution by the results of strong ground motion,which indicates that the earthquakes with magnitude 7 or above in this area will cause serious damage on the county of Jingtai,Lanzhou and Jingyuan with the intensity above ?.