Fast report: source rupture model analysis of the 2025 Dapu earthquake, Taiwan

Abstract A joint source inversion analysis integrating teleseismic waveforms, near-field GNSS coseismic displacement, and strong ground motion data was performed to investigate the rupture process of the 2025 M L 6.4 Dapu earthquake in southwest Taiwan. The inversion incorporated two nodal fault planes determined by the real-time moment tensor system, with results indicating that the west-dipping fault plane provided the best fit across all three datasets. Rupture initiated at approximately 10 km depth and propagated southwestward. A single prominent asperity was identified ∼ 10 km from the epicenter in the southwestern region, characterized by a compact slip area with a maximum slip of ∼ 30 cm and an estimated stress drop of 1.0 MPa. The inversion results suggest that the primary seismogenic structure is a west-dipping blind thrust fault in the middle-to-deep crust beneath the detachment. This fault does not reach the surface and exhibits limited interaction with the shallow east-dipping structures. These findings highlight the need to reassess deep structures beneath the detachment in southwest Taiwan.