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

We 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. Plain Language Summary: More probable location and size of future large earthquakes can be anticipated if we accurately know the present‐day distribution of interseismic fault coupling. Knowing date of the latest large earthquake, one can infer slip deficit and estimate the energy available for forthcoming seismic ruptures. Here, we focus on the Xianshuihe‐Anninghe‐Zemuhe‐Xiaojiang fault system in Tibet, which is the largest strike‐slip fault crossing southwestern China. Historical records attest numerous earthquakes during the last few centuries, but the fault has remained relatively silent in the past few decades. We use GPS data spanning nearly 20 years to investigate the present‐day interseismic fault coupling along the fault system. We find the Anninghe, Zemuhe, and Xiaojiang faults have accumulated enough energy for several Mw > 7 earthquakes. However, our results show that the northern segment called the Xianshuihe fault is not locked, suggesting a relatively low energy accumulation rate and seismic potential, despite a long history of frequent earthquakes. Finally, we identify a new ∼30 km‐long creeping section on the Xianshuihe fault, whose creep rate show a transient behavior, possibly induced by the effect a ∼200 km remote earthquake that occurred in 2008. Key Points: Highly heterogeneous interseismic coupling along the Xianshuihe‐Xiaojiang fault system, with the northern Xianshuihe fault predominantly creeping at depthSurface creep observed during 4 decades after the 1973 M 7.6 Luhuo earthquake has endedA new ∼30 km‐long transient creeping segment on the Xianshuihe fault, with creep rate increasing after the 2008 Mw 7.9 Wenchuan earthquake [ABSTRACT FROM AUTHOR]