Heterogeneous Interseismic Coupling Along the Xianshuihe‐Xiaojiang Fault System, Eastern Tibet

Abstract

AbstractWe use Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data to quantify the interseismic coupling along the Xianshuihe‐Xiaojiang fault system (XXFS). Our results confirm 7–11 mm/a of left‐lateral strike‐slip motion along the XXFS. South of the Shimian County, high interseismic coupling is found down to 20 km‐depth along the Anninghe‐Zemuhe fault. A second 130 km‐long section, highly coupled down to 10–15 km‐depth, is identified along the northern Xiaojiang fault. North of the Kangding County, the Xianshuihe fault appears to be predominantly creeping at depth. Previously identified long‐lasting surface creep following the 1973 M 7.6 Luhuo earthquake has now ended, possibly marking the initiation of a new period of stress accumulation and progressive relocking of the fault. Farther south along the fault, we identify a ∼30 km‐long section (∼30.2°–30.4°N) creeping at ∼7 mm/yr. Furthermore, creep accelerated by ∼2 mm/yr during the 2008–2014 period, possibly as a result of the static Coulomb failure stress increment induced by the 2008 Mw 7.9 Wenchuan earthquake, that occurred ∼200 km northeast of it. The 2014 Mw 5.9 Kangding earthquake occurred along the creeping section at the end of the period of accelerated creep. Finally, taking advantage of the long historical records of past large earthquakes available since 1327, we quantitatively compare the moment budget along the XXFS. Results highlight that along the Anninghe, Zemuhe, and Xiaojiang faults, moment deficit for Mw > 7 earthquakes has now accumulated.