Fault geometry and slip distribution of the 2025 MW5.8 Xinjiang Aheqi earthquake revealed by InSAR observations

On December 4, 2025, an M W 5.8 earthquake struck Aheqi County, located in the southern Tian Shan, approximately 24 km from the epicenter of the 2024 M W 7.0 Wushi earthquake. This proximity has prompted questions regarding the structural relationship and potential stress transfer between the two events. To investigate the coseismic deformation and fault slip characteristics of the Aheqi earthquake, we employ ascending and descending Sentinel-1 InSAR data. Geodetic inversion reveals rupture of an NNE-dipping fault (dip = 36.9°, rake = 113.9°) exhibiting right-lateral reverse oblique slip, with slip exceeding 0.2 m concentrated at depths of 5-9 km and a peak value of ∼1.2 m at ∼8 km depth. The absence of surface rupture and the marked contrast in fault geometry relative to the Wushi seismogenic fault indicate that the Aheqi event occurred on a previously unrecognized blind structure rather than representing a simple along-strike continuation of the Wushi rupture. Coulomb stress modeling further shows that the 2024 Wushi earthquake imposed a positive stress perturbation on the Aheqi fault plane. We infer that the 2025 Aheqi earthquake was likely promoted by coseismic and postseismic stress transfer within a structurally complex intracontinental fault system. These findings provide new insight into stress redistribution in the southern Tian Shan and have implications for regional seismic hazard assessment.