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

摘要

In this study, 1338 relocated earthquakes (M-s >= 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 M(w)7.1 earthquake.