Dynamic Simulation of Fault Rupture Propagation: A Symmetric Comparison of Normal and Reverse Faulting

Conventional assessments of fault rupture propagation in overlying soil layers often rely on static or quasi-static analysis, neglecting the dynamic nature of fault displacement and inertial effects. This study develops a comprehensive simulation method for the entire process from rupture initiation to propagation under dynamic fault displacement. The method integrates a nonlinear elastic constitutive model based on the Hardin backbone curve with a non-uniform input technique for seismic waves on both sides of the fault using viscoelastic artificial boundaries. To demonstrate the distinct capabilities of this dynamic method, we conduct a comparative study on normal and reverse faulting driven by fault displacement time histories of identical magnitude but opposite sense. The simulations reveal that: (1) the fault displacement required for rupture initiation and propagation remains consistent between dynamic and quasi-static analyses; (2) crucially, the proposed method captures the transient dynamic response of fault rupture in the overlying soil. The study confirms that the proposed dynamic simulation framework is essential for resolving transient peak responses, oscillatory behavior, and deformation features associated with different faulting mechanisms, providing a more realistic tool for seismic risk assessment compared to conventional static approaches.