Unzipping of the Conjugate Fault System During the 2024 Mw7.4 Hualien Earthquake

Abstract On 2 April 2024, a Mw7.4 earthquake struck Taiwan's eastern coast near Hualien City. The fault responsible for the mainshock remained under debate due to the region's complex plate boundary system and intricate fault interactions. To determine the fault plane and resolve the rupture process, we analyzed local and teleseismic waveform recordings, along with near‐field and satellite geodetic data. We employed Slowness‐Enhanced Back‐Projection and Finite Fault Inversion techniques across seismic and geodetic data sets. Our analysis revealed that the rupture propagated on the east‐dipping Longitudinal Valley Fault (LVF) and its west‐dipping conjugate fault. The rupture started on the LVF and reached the conjugate fault at ∼8 s, after which slip occurred simultaneously on both faults. The aftershock distribution validated the fault geometry. The 2024 mainshock demonstrated the seismic potential of the LVF and its role in accommodating the thrust component of strain accumulation from the plate collision near Hualien.