Static Stress Triggering Effect on the Surrounding Major Faults and Aftershocks of the 2024 M 7.4 Earthquake in Hualien, Taiwan

Earthquakes not only release the long-term accumulated stress on the seismogenic fault but may also increase the stress on some surrounding faults or other segments of the seismogenic fault, thereby raising the seismic risk on these faults. This study investigates the impact of the April 2, 2024, Mw 7.4 earthquake in Hualien, Taiwan, on the surrounding faults and aftershocks. We analyze stress-triggering effects by calculating Coulomb stress changes (ΔCFS) using rupture models and focal mechanism data. Historical focal mechanism nodal planes serve as receiver fault parameters for ΔCFS calculations. Our findings indicate significant Coulomb stress loading on the Longitudinal Valley fault and Central Range structure due to the mainshock, promoting their seismic activity. Loading effects vary by fault type, with thrust and strike-slip faults experiencing more stress loading than normal and odd faults. Conversely, the rupture’s coseismic slip concentration area shows predominant stress unloading, inhibiting seismic activity in the region. Aftershocks mainly experience increased ΔCFS, suggesting that the stress-triggering induced by the mainshock considerably influences the earthquake sequence evolution. These insights are crucial for understanding aftershock patterns and enhancing seismic hazard assessments.