Bayesian Inference of Fault Slip and Coupling Along the Tuosuo Lake Segment of the Kunlun Fault, China

Integrating newly-processed Interferometric Synthetic Aperture Radar (InSAR) and available Global Positioning System (GPS) data, we obtained a dense interseismic velocity field across the Tuosuo Lake segment of the Kunlun fault. Using a Bayesian approach, we obtained the spatial distribution of fault slip and coupling. The slip rate below the locking depth, which represents contemporary steady-state faulting, demonstrates an overall decrease, and decreases non-monotonically toward the eastern fault tip in the range of similar to 5-11 mm/a. Two strongly locked zones are identified, extending 100-120 km along-strike and being separated by narrow sections of moderate coupling. These locked zones were likely ruptured during the 1937 M 7.5 Huashixia earthquake. The estimated moment accumulation rate provides a recurrence time of 428 +/- 57 years for an earthquake similar to the 1937 event. The Maduo Mw 7.3 earthquake on 21 May 2021 imposed stress loading on the locked zones, equivalent to tectonic loading of similar to 10 years, implying increased seismic hazard along the Kunlun fault. Plain Language Summary Strike-slip faults in Tibet are central to our understanding of the ways in which continental lithosphere deforms in response to the ongoing India-Eurasia collision. As a key parameter of faulting, fault slip rates have been well investigated for some major strike-slip faults in Tibet (e.g., the Altyn Tagh, Xianshuihe-Xiaojiang, and Haiyuan faults). However, the slip rate along the Kunlun fault, one of the main faults in central Tibet, remains controversial, especially along its eastern segment. In this study, from one track of descending Sentinel-1A Interferometric Synthetic Aperture Radar (InSAR) images, we obtained a dense velocity field across the Tuosuo Lake segment of the Kunlun fault. We applied a Bayesian dislocation model jointly to the InSAR and Global Positioning System data to obtain the spatial distribution of fault slip and coupling. Our detailed investigation demonstrates that slip rates vary, but overall decrease toward the eastern fault tip. Our results provide new insight into slip rate variation along the eastern Kunlun fault and suggest a similar to 430 year recurrence interval for large earthquakes along this segment (i.e., Mw 7.5, similar to the 1937 M 7.5 Huashixia earthquake).