Characterizing creeping faults using InSAR: a case study of the Xianshuihe Fault

Abstract:

The Xianshuihe Fault is located at the eastern boundary of the Tibetan Plateau and is one of the most active faults in China. It is associated with substantial seismic potential, with more than 20 Mw>6 earthquakes since 1700. The fault has been documented to be creeping at the surface for decades; however, the details of the distribution of creep in space and time are not well resolved. In this study, we use more than 3 years of Sentinel-1 InSAR data from ascending and descending orbits to retrieve the subtle interseismic deformation signal in the Xianshuihe Fault region. LOS velocity maps are further decomposed into fault parallel and vertical components. We identified two ~25-km-long creeping segments indicated by a sharp velocity gradient across the fault. To better quantify the along strike variation of the surface creep, we determine velocity profiles and estimate the surface fault creep rate every 2km along the fault. The results indicate high spatial variability ranging from 0~4 mm/yr. To investigate if the surface creep is modulated by seismic events or other external factors (e.g., creep acceleration or deceleration, afterslip and triggered creep transients), a time-series analysis of persistent scatters along the fault is conducted.