Discrete element modeling of earthquake-induced fault rupture evolution: The 2024 Mw7.4 Hualien Taiwan earthquake

Surface rupture caused by a strong earthquake is extremely hazardous to the safety of people’s lives. Understanding the rupture evolution mechanism of co-seismic faults and assessing the influence of fault area propagation is essential for disaster prevention and resilience. Since 2000, Hualien and nearby areas in eastern Taiwan have experienced 33  earthquakes, which is a good area to study the evolution of fault rupture. In this study, we propose a dynamic discrete element model to explain fault rupture evolution and use it to analyze the rupture behavior of the 2024 Mw7.4 earthquake of Hualian. This earthquake occurred near the northern Longitudinal Valley Fault (LVF), where crustal movement can be seen from the Milun Fault (MF) to the north part of the LVF. We use ALOS-2 data to identify major faults and the Interferometric Synthetic Aperture Radar (InSAR) method to access the spatial displacement on the surface of the study area. In order to simulate the complex geometry and corresponding deformation of the co-seismic rupture surface under the compound influence of multiple faults, we set a rock biaxial simulation test to obtain effective model parameters. We then established a series of dynamic models with different bond types and strengths based on the discrete element method. The model demonstrates the deformation along the fault rupture surface, corresponding to the observation results. The simulation results cover the rupture behavior of the fault and the displacement of the shallow fault under long time series, which can provide a reference for the subsequent seismic hazard assessment and fault displacement analysis.