Post-seismic Coulomb stress simulation and seismic hazard analysis of the 2025 Myanmar M_W7.7 earthquake

On March 28, 2025, an M_W7.7 earthquake struck Myanmar, with the epicenter located in the central segment of the Qinghai–Xizang–Yunnan–Myanmar–Indonesia η-type structure. This region hosts a series of active faults, including the right-lateral Sagaing Fault and the Red River Fault in southwestern Yunnan. Based on the fault geometry model published by Zhang et al. and the Crust1.0 layered medium model, this study simulates the co-seismic and post-seismic Coulomb stress changes at depths of 5, 10, and 15 km on the main fault zones within the study area. The results indicate that the earthquake was dominated by Coulomb stress unloading, with localized loading observed at the northern and southern ends of the rupture. On the Sagaing Fault, Coulomb stress changes were dominated by unloading: average decreases ranged from −2.4 to −4.7 bar across all depths and timescales, indicating a low likelihood of large-scale rupture on that fault. However, in the northern segment of the rupture, localized stress loading exceeded the critical threshold of 0.1 bar, suggesting a possible enhancement of local seismic hazard. In southwestern Yunnan, co-seismic Coulomb stress loading at all depths ranged from −0.37 × 10⁻² to 1.8 × 10⁻² bar. Post-seismic stress changes were minor, with a maximum of 3.2 × 10⁻³ bar. These results imply that the M_W7.7 event induced only subtle adjustments to the long-term tectonic stress field in southwestern Yunnan; nevertheless, the presence of stress-loading regions within seismic gaps warrants continued attention to potential hazard.