Recent Seismic Activity in Hualien, Taiwan: Geological Context and Event Analysis

Taiwan lies at the convergent boundary between the Eurasian Plate and the Philippine Sea Plate, where oblique collision drives rapid crustal deformation and frequent seismicity. The eastern region around Hualien City occupies the northern Longitudinal Valley, a major suture zone marking the plate boundary. Here, the Philippine Sea Plate subducts northwestward beneath the Eurasian Plate at rates exceeding 7 cm per year, producing both shallow crustal earthquakes and deeper events along the Wadati-Benioff zone. On 2 April 2024 at 23:58 local time, a magnitude 7.4 earthquake struck 15 km south of Hualien City at a focal depth of 40 km. The event originated within the collisional deformation belt, consistent with the regional stress regime dominated by northwest-southeast compression. Strong ground shaking was reported across eastern Taiwan, with the rupture likely involving reverse faulting on structures associated with the plate interface or nearby imbricate thrusts. Seismicity records since 2000 highlight recurring large events near Hualien. The 2 April 2024 earthquake was preceded by a magnitude 7.1 event on 31 March 2002 located 67 km ENE of the city at a comparable depth range. That earlier shock occurred approximately 76 km from the 2024 epicenter and similarly reflected the ongoing plate-boundary tectonics. Both events underscore the persistent seismic hazard along this segment of the margin, where accumulated strain from plate convergence is periodically released. Geological mapping of the Hualien area reveals a complex assemblage of metamorphic rocks, ophiolitic fragments, and Quaternary sediments deformed by active faults. The Longitudinal Valley Fault system accommodates much of the lateral and vertical motion, while subsidiary structures transfer slip into the Central Range. Historical instrumented records and paleoseismic studies indicate recurrence intervals for magnitude 7+ earthquakes on the order of decades to centuries in this corridor. The 40 km depth of the 2024 mainshock places it near the transition from brittle to ductile behavior, where fluids and temperature influence rupture dynamics. Aftershock distributions following such events typically migrate along the plate interface and adjacent faults, providing data for refining seismic hazard models. Regional monitoring networks operated by Taiwan’s Central Weather Administration continue to track post-seismic deformation using GPS and strong-motion instruments. Understanding these earthquakes requires integration of plate-tectonic theory with local structural geology. Continued convergence between the Philippine Sea and Eurasian plates ensures that Hualien and surrounding areas will experience future large-magnitude events. Mitigation strategies therefore emphasize building codes, early-warning systems, and public preparedness calibrated to the documented seismic potential of the northern Longitudinal Valley.

References

United States Geological Survey Earthquake Catalog (event parameters and historical data). Central Weather Administration, Taiwan (regional seismic monitoring records).