Seismic rupture and earthquake sequence along the Ganzi-Yushu fault in Eastern Tibet: From kinematics to dynamics

The Ganzi-Yushu fault, striking in a northwest direction with a length of approximately 500 km, delineates the boundary between the Bayan Har block and the Qiangtang block. Due to the ongoing collision between the Indian plate and Eurasia plate and the resultant eastward extrusion process in the Tibetan Plateau, the fault system is characterized by rapid left-lateral strike-slip and frequent major earthquake events. The 2010 M_S 7.1 Yushu earthquake ruptured the northwestern segment of the fault, resulting in significant casualties and property losses. Apart from the 2010 Yushu earthquake, this fault has experienced four M > 7.0 earthquakes in the past 300 years, marking it as one of the most seismically active fault systems in the Tibetan Plateau.

In this study, we use Sentinel-1 InSAR data spanning from 2014 to 2023 to derive the interseismic velocity fields along the Ganzi-Yushu fault. Based on the interseismic velocity field, we derive the slip rates and interseismic coupling distribution along the Ganzi-Yushu fault using elastic block model. The results indicate left-lateral slip rates of 4.0~6.5 mm/yr along the Ganzi-Yushu fault. We identify five locked segments along strike, which has good consistency with historical earthquakes.

To assess the earthquake potential along the Ganzi-Yushu fault, we simulate earthquake rupture sequences using quasi-dynamic earthquake cycle model. We set the friction coefficient of the rate- and state-dependent friction law according to the interseismic coupling model, thereby obtaining interseismic slip rates in numerical simulations that align with the kinematic results. Our quasi-dynamic earthquake cycle model generates both single- and multi-segment ruptures with magnitudes approximating those inferred from the historical events. Owing to variations in seismogenic width and slip rate, different segments exhibit distinct recurrence intervals, which is consistent with the results from geological surveys. The locations of nucleation and the slip history on fault determine whether a rupture can propagate across multiple segments and generate a major event. By integrating the kinematic model with the physics-based seismic cycle simulations, our results shed light on the earthquake potential along the Ganzi-Yushu fault.