Source Characteristics of the 2025 Mw 6.0 Aheqi Earthquake: Possible Relationship to the 2024 Mw 7.0 Wushi Earthquake

The 4 December 2025 Mw 6.0 Aheqi earthquake occurred on the Maidan–Shayilamusi Fault system in the western southern Tian Shan, approximately 23 months after the 2024 Mw 7.0 Wushi earthquake. We used ascending- and descending-track Sentinel-1A differential interferometric synthetic aperture radar (DInSAR) observations to map coseismic line-of-sight (LOS) deformation, jointly invert fault geometry and distributed slip, calculate Coulomb failure stress changes, and evaluate sequence association using earthquake-catalog statistics and an epidemic-type aftershock sequence (ETAS) model. The deformation field is elongated NEE–SWW, with maximum displacement toward the satellite of approximately 6 cm. The preferred model has a strike of 242°, dip of 40°, rake of 77°, and maximum slip of 0.21 m concentrated at depths of 4.89–7.46 km, corresponding to Mw 5.91. The joint inversion yields an RMSE of 0.0145 m. Coulomb stress calculations indicate positive ΔCFS at the Aheqi source within the principal rupture-depth interval of 4.89–7.46 km across all three tested receiver-fault geometries. For the preferred geometry, ΔCFS reaches +6.16 bar at the slip-centroid depth of 6.18 km and is close to zero (+0.29 bar) at 10 km, where its sign varies among the tested geometries. At 15 km, ΔCFS is negative for all three geometries. ETAS stochastic declustering assigns the Aheqi event a total triggered-component probability of 82.6% and a background-component probability of 17.4%. Separate attribution analysis yields a 65.7% probability of belonging to the Wushi mainshock’s descendant sequence and a 0.5% probability of direct triggering by the Wushi mainshock. Together with the spatiotemporal compatibility of the two events, these results support a possible interaction within the segmented Maidan–Shayilamusi Fault system, although they do not establish deterministic causation or uniquely identify the physical triggering pathway. The modeled stress pattern also highlights nearby positively loaded fault segments for continued monitoring.