Co-seismic Rupture Characteristics of the 2025 Mw 5.8 Akqi Earthquake and Its Relationship with the 2024 Mw 7.0 Wushi Event

Objectives: On December 4th, 2025, a Mw 5.8 earthquake occurred in Akqi County, Kizilsu Prefecture, Xinjiang, located approximately 24 km from the 2024 Mw 7.0 Wushi earthquake. The focal rupture characteristics of this event, as well as its structural and stress relationships with the previous major earthquake, remain unclear. The aims are to derive the coseismic deformation field, invert the source parameters, and clarify the focal mechanism, fault geometry, and potential stress interactions between these two seismic events. Methods: Three pairs of Sentinel-1 ascending and descending InSAR data were employed to determine the coseismic deformation field of the Akqi earthquake, revealing a maximum line-of-sight displacement of approximately 6 cm. Based on the InSAR observations, the earthquake source parameters were inverted using an elastic half-space rectangular fault model. A comparative analysis with the source mechanism of the 2024 Wushi earthquake was also conducted, and Coulomb stress analysis was performed to assess stress interactions between the two events. The Bayesian inversion method was applied to effectively address uncertainties in fault geometry and source parameter determination. Results: The fault plane of the Akqi earthquake strikes around 272° and dips approximately 50°, representing an oblique thrust fault dominated by reverse motion with a minor strike-slip component. The rupture was mainly concentrated at depths of 6–9 km and did not reach the surface, classifying it as a blind thrust rupture event. Comparative analysis with the 2024 Wushi earthquake indicates consistency in spatial distribution and fault system characteristics. Coulomb stress analysis suggests that the Akqi earthquake occurred within a stress zone influenced by coseismic stress changes from the Wushi earthquake, supporting a possible stress-triggered relationship. The Bayesian inversion approach effectively constrained fault geometry and slip distribution, demonstrating strong adaptability in handling complex fault systems. Conclusions: The 2025 Akqi Mw 5.8 earthquake is identified as a blind thrust event exhibiting oblique-reverse faulting characteristics. It shows notable consistency with the 2024 Wushi earthquake in spatial distribution and fault system attributes, while Coulomb stress analysis further indicates stress interaction between the two events. These findings provide insights into seismogenic mechanisms and stress transfer processes within the southern Tianshan seismic belt, contributing to improved seismic hazard assessment and offering references for understanding earthquake triggering and fault system dynamics in tectonically active regions.