Interseismic Fault Movement of Xianshuihe Fault Zone Based on Across-Fault Deformation Data and InSAR

Abstract

Tectonic movement is closely related to earthquake preparation. Across-fault sites and InSAR data are applied to reveal crust deformation from different precision, different temporal scale, and different spatial scale. In this paper, Xianshuihe fault zone is taken as an example; dislocation model in near-fault field is derived from screw dislocation model proposed by Savage and Burford (1973), which can reveal the locking information of the across-fault site using baseline data. Locking depth of each across-fault site on Xianshuihe fault zone is calculated using baseline data, which indicates that the locking depth of Laoqianning across-fault site is about 18 km and the locking depth of other sites is shallow. Time series analysis of SBAS-InSAR is used to study interseismic tectonic deformation. Deformation field from InSAR reveals the left-lateral slip property of Xianshuihe fault zone. The average locking depth is about 2–4 km calculated by the pixels’ slip rate around in near-fault field, which indicates that locking depth is shallow and consistent using InSAR data as well as across-fault data. Screw model is used to obtain the best-fitting result of fault locking depth and slip rate. Layered dislocation model is put forward to explain shallow locking depth of fault zone. According to the theory of fault-slip deficit and seismic moment equilibrium, accumulative seismic moments caused by fault slip and the release amount of MS ≥ 5.0 earthquakes are calculated to estimate seismic risk of study area. All results indicate that Qianning segment of Xianshuihe fault zone is the future danger area with strong earthquakes.