[S-CG50] Earthquakes, Tsunamis, Seismotectonics, and Hazard Potential of the Ryukyu Trench and Okinawa Trough

[SCG50-03] Spatiotemporal Patterns of the April 2, 2024, Hualien Earthquake Sequence and Finite Fault Solutions of Significant Aftershocks

*Yopi Ruben Serhalawan^1,2,4, Mei Chien³, Po-Fei Chen², Wei-Li Chen², Hsuan-Yu Kuo² (1.Taiwan International Graduate Student - Earth System Sciences, Academia Sinica and National Central University, Taiwan, 2.Department of Earth Sciences, National Central University, Taiwan, 3.Department of Earth, Environmental, and Planetary Sciences, Rice University, 4.The Indonesian Agency for Meteorological, Climatological and Geophysics, Indonesia)

Keywords:The 2024 Mw 7.4 Hualien earthquake, Spatiotemporal Patterns of Aftershocks, Significant Aftershocks, Finite Fault Inversion

The 2024 Mw 7.4 Hualien earthquake occurred on April 2 at a depth of 22 km beneath the coast of the northern Longitudinal Valley (LV) in eastern Taiwan. Throughout the remainder of the month, the Hualien earthquake sequence was characterized by more than 10 significant aftershocks (ML > 5.8) and intense seismic activity, which peaked immediately after the mainshock and again on April 22. Using data from a temporary SmartSolo array and permanent local networks, we applied a machine-learning phase picker (PhaseNet), rapid earthquake association and location (REAL), a least-squares location method (VELEST), and a high-precision relative location method (hypoDD) to analyze the spatiotemporal patterns of the earthquake series. To investigate the finite fault solutions of significant aftershocks (AF1 to AF13), we conducted joint inversions of body waves (P and SH) and strong-motion data using the Wavelet and Simulated Annealing SliP (WASP) inversion method. Our hypoDD results and Regional Moment Tensor (RMT) solutions were used to define the geometry of fault planes for finite fault inversion. The REAL catalog achieved a 92% recall rate compared to the CWA catalog, confirming similar spatial distribution and magnitude trends. The VELEST catalog, using density-based spatial clustering, identified two main aftershock clusters: (1) an immediate aftershock sequence with high seismic activity northward and lower activity in the asperity zone, and (2) a spatiotemporally confined swarm. Finally, a key spatiotemporal feature of the hypoDD catalog is its strong alignment with the fault planes of significant aftershocks.