Locking depth, slip rate, and seismicity distribution along the Daofu–Kangding segment of the Xianshuihe fault system, eastern Tibetan Plateau

Abstract

In this study, 1338 relocated earthquakes (Ms ≥ 1.6) from 1981 to 2018 and 53 GPS velocities from 2004 to 2017 were processed to obtain the geometry and kinematic characteristics of the Daofu–Kangding segment of the Xianshuihe fault system in southwestern China. By analyzing the seismicity depth distribution of the Selaha–Kangding fault, we inferred its three branches, the Yalahe fault, Selaha fault, and Zheduotang fault converged into one fault at a depth of approximately 15 km and that a flower-shaped structure was observed above this depth. Furthermore, based on a 2D elastic dislocation model, the creep rates, creep depths, slip rates, and locking depths of the Daofu–Kangding segment were analyzed. In case of the Daofu–Qianning fault, the obtained left-lateral slip rate was 4.5 ± 1.1 mm/a and the locking depth was 5.3 ± 1.9 km. Because the fault creep rate from a depth of 2.6 km to the surface was 1.3 ± 1.0 mm/a, the Daofu–Qianning fault cannot generate earthquakes having magnitudes of greater than 7 in the near future. However, the slip rates were 7.5 ± 1.6, 2.3 ± 1.5, and 1.9 ± 1.5 mm/a by assuming a locking depth of 15 km for the Selaha fault, Yalahe fault, and Zheduotang fault, respectively. Furthermore, because the creep depth of the Selaha fault was 3.4 ± 1.6 km and the creep rate was 7.5 ± 2.8 mm/a, the accumulated seismic moment since 1725 corresponded to a Mw7.1 earthquake.