Research on the Locking and Slip Deficit of the Anninghe Fault Zone Constrained by Electrical Structure

The Sichuan-Yunnan Block, located on the southeastern margin of the Tibetan Plateau, is one of the regions with the highest tectonic activity and seismicity in China. However, the Anninghe Fault Zone (ANHF) has not produced an M≥7.0 earthquake for centuries, which warrants a systematic assessment of its seismic hazard. Based on deep electrical resistivity structural models derived from four magnetotelluric sounding profiles across the eastern boundary fault system of the Sichuan-Yunnan Block, this study constrains the deep geometric configuration of major faults and yields high-fidelity subsurface constraints on the Anninghe-Zemuhe Fault Zone (ANHF-ZMHF). Using the negative dislocation theory and fault locking model, we derive robust estimates of locking degree and slip deficit rate along the ANHF. Our results reveal prominent strike-wise segmentation in fault locking and slip deficit along the ANHF-ZMHF. The Shimian segment is strongly locked from the surface down to ~20 km depth, with pronounced slip deficit and significant elastic strain accumulation. The segment north of Mianning remains largely unlocked and dominated by aseismic creep. The Mianning-Xichang segment acts as a zone of high coupling with strong fault locking. In contrast, the segment south of Xichang exhibits clear locking only in the shallow crust, while its deeper portion remains mostly unlocked in a creep-dominated state. Cumulative strain energy estimates indicate that the fault system is capable of generating strong earthquakes with magnitudes of M_W6.95-7.35. Overall, the locked Shimian segment and the strongly locked Mianning-Xichang segment are currently at high risk of strong earthquake occurrence, whereas the unlocked segment north of Mianning and the creep-dominated southern Xichang segment pose relatively low short-term seismic hazard. This discrepancy is attributed to weak fault coupling and ongoing stress relaxation via aseismic slip in the latter zones.