Evaluation of earthquake dynamic rupture simulation parameters: A case study on the northern segment of the Shunyi-Liangxiang fault

Numerical simulation of physics-based scenario earthquakes is recently one of the research focuses in seismology. This type of simulation requires certain parameter assumptions like fault geometry, regional stress fields, and nucleation conditions, all of which carry considerable uncertainty. This study utilizes the northern segment of the Shunyi-Liangxiang fault in the Beijing region as a case study, simulating a magnitude 7 scenario earthquake on this fault and further examines the effects of various initial parameters on dynamic rupture modeling. We first construct the fault geometry model of the north segment of the Shunyi-Liangxiang fault, the velocity structure model around the fault, the initial stress model on the fault plane, and the friction parameters model. We then simulate the spontaneous dynamic rupture of a scenario earthquake with magnitude of 7 using the curved grid finite-difference method. And the rupture propagation process, the final slip distribution, and the rupture velocity on the fault plane, as well as the moment releasing rate are obtained. The simulation results indicate that the fault slip of this scenario earthquake is predominantly characterized by strike-slip motion. Due to the blocking effect at the fault bends, the rupture area is constrained within the first 20 km of the northern segment of the Shunyi-Liangxiang Fault. Moreover, the rupture on the fault plane propagates at a sub-shear speed after initiating from the nucleation zone. Based on this earthquake rupture model, we discuss the qualitative effects of the stress configuration parameters, friction parameters, rupture initiation conditions in the nucleation patch, and nucleation locations on the rupture propagation. The simulation results show that the maximum principal stress azimuth θ, the location of the nucleation patch along the fault strike, and the radius of the nucleation patch have the greatest influence on the fault rupture dynamics. These influences are due to significant changes in the projected stresses on the fault plane under different stress azimuths, change in the projected stresses caused by changes in fault strike, and stress perturbation near the nucleation patch. The ratio between fluid pressure and lithostatic stress λ, the ratio between minimum horizontal principal stress and vertical principal stress kh, the stress factor R, the static friction coefficient μs, the dynamic friction coefficient μd, and the critical slip-weakening distance Dc on the fault plane have a strong influence on the rupture propagation. The increase or decrease of these parameters′ value results in changes in initial stress distribution on the fault plane, the strength of the fault plane, and stress drop, consequently affecting the final slip, the rupture speed on the fault plane, and the timing of release of the seismic moment. These conclusions can provide guidance for the simulation of physics-based scenario earthquakes or natural earthquakes performed on other active faults.