The 2024 Mw 7.3 Hualien Earthquake Sequence: Aftershock-Constrained Fault Geometry and Static Stress Triggering Analysis
Abstract
The 2024 Mw 7.3 Hualien earthquake represents a significant seismic event in a highly complex tectonic setting, providing a critical opportunity to constrain complex fault geometries and evaluate stress triggering mechanisms. We compiled a high-resolution aftershock catalog of 23,748 events from continuous seismic waveforms recorded over three months. This catalog systematically documents the spatiotemporal evolution of the 2 April 2024 Mw 7.3 Hualien mainshock and its aftershocks. The aftershock distribution outlines a conjugate fault system composed of the east-dipping Longitudinal Valley fault and the west-dipping Central Range fault, with clear depth-dependent variations in geometry. The seismicity front expanded as a logarithmic function of time, consistent with afterslip-driven migration of the Hualien earthquake sequence. The aftershocks predominantly occurred around and outside of the high-slip periphery, consistent with stress reduction within high-slip areas and stress concentration at the periphery and gradient zones of the high-slip area. Coulomb stress calculations further suggest that static stress transfer from the mainshock contributed to the occurrence of several major aftershocks. These results highlight the role of stress interactions in controlling aftershock distribution and provide constraints on postseismic hazard assessment in eastern Taiwan.