Tectonic features of the deformation front in western Taiwan and implications for recent earthquake clusters

The Western Foothills Belt of Taiwan, shaped by the collision between the Eurasian and Philippine Sea plates, exhibits high seismicity concentrated along its deformation front. For example, Chongpu region in southwestern, Taiwan, characterized by active thrust faulting and fold structures, represents a zone of elevated seismic hazard. The most significant historical event in the area was the 1941 Chongpu earthquake (ML 7.1). Since the 1999 Chi-Chi earthquake (Mw 7.6), however, seismicity has predominantly involved smaller earthquakes. Notably, two earthquake swarms near the 1941 epicenter in 2017 and 2018 have raised questions about their potential implications. Similar phenomena have been observed in the Noto Peninsula, Japan, where prolonged earthquake swarms preceded the 2024 Mw 7.5 Noto earthquake. Previous research highlights the highly fractured subsurface environment beneath the Chongpu region, suggesting the possibility of analogous swarm patterns. This study aims to investigate the spatiotemporal characteristics of recent earthquake cluster in the Chongpu area, examining their relationship to the 1941 event. By conducting seismic data inversion to derive subsurface imaging, integrating these results with structural analysis of fault-fold systems, and assessing stress distributions from geological surveys, this research seeks to elucidate the seismogenic processes at the deformation front. The findings are expected to enhance the understanding of earthquake clusters mechanisms, evaluate their potential as precursors to major seismic events, and contribute to improved earthquake hazard assessment and disaster mitigation in urban settings.