The Seismogenic Potential of the Xianshuihe-Xiaojiang Fault System, Eastern Tibet: A Probabilistic Seismic Moment Budget Approach Incorporating Fault Coupling Heterogeneity

Summary The Xianshuihe-Xiaojiang Fault System (XXFS), with slip rates of centimeters per year, is a major tectonic boundary accommodating southeastward extrusion of the Tibetan Plateau. Stretching over ~1,000 km through the densely populated Sichuan and Yunnan provinces in western China, it is particularly important to evaluate its potential for generating destructive earthquakes. This study systematically evaluates the XXFS within a physically grounded probabilistic framework by integrating geodetically modeled interseismic coupling, seismicity, empirical magnitude-area scaling laws, and barrier effects of creeping zones during dynamic rupture. We assess a range of rupture scenarios and obtain most probable maximum magnitudes of Mw 7.4 for the Xianshuihe fault, Mw 7.3 for the Anninghe-Zemuhe Fault, and Mw 7.2 for the Xiaojiang Fault, with corresponding fault-level recurrence of ~300, ~1 500 and ~170 years. The probabilities of occurrences of Mw 7.0 earthquake are higher along the northern and southern Xianshuihe, southern Anninghe, northern Zemuhe, and southern Xiaojiang segments. By assimilating geodetic and seismic data into a probabilistic framework that incorporates moment balance and rupture dynamics, our study provides a physics-based foundation for assessing regional seismic hazard in this tectonically active area. The approach is generalizable and can be applied to other fault systems where seismicity, basic geometry and geodetic coupling are constrained.