The Relationship between Clustered-Aftershocks and 3D-Fault Models in Eastern Taiwan

The aftershock sequence typically consists of numerous seismic events, with their distribution exhibiting clustering characteristics. In geologically complex areas, such as the convergence boundary between the Eurasian and Philippine Plate in eastern Taiwan, it is challenging to explain the relationship between seismic events and regional structures. This area has experienced several disastrous earthquakes in recent years, including the Hualien earthquake (Mw 6.4) in 2018, the Chihshang earthquake (Mw 7.0) in 2022, and the Hualien earthquake (Mw 7.3) in 2024. Here, we aim to explore the relationship between the aftershock sequences of three events and the known active faults. Firstly, we apply the algorithm to cluster aftershocks. We analyze aftershock sequences for three events with local magnitudes greater than 3, spanning 45 days after the mainshock. Secondly, we examine the relationship between these clustered sequences and the 3D fault models developed by National Science and Technology Center for Disaster Reduction (NCDR). The results reveal that the aftershock sequence of the 2018 Hualien earthquake can be divided into five clusters, while the 2022 Chihshang earthquake can be divided into seven clusters. The mainshocks are separately located at clusters which have the largest number of aftershocks within their respective sequences. The aftershock sequence of the 2024 Hualien earthquake can be divided into eight clusters. The mainshock is located at a cluster with minor number of aftershocks, which is distributed along the Lingding Fault. Additionally, 3D visualization is employed to better illustrate the relationship between earthquake sequences and active faults, as well as to study potential earthquake mechanisms.