InSAR observations reveal interactions between seismic and aseismic slip during and after the 2016 Mw 6.6 Muji earthquake

Studying the relationship between coseismic slip and aseismic creep helps better understand the seismic and aseismic behavior of crustal faults. We use multi-platform synthetic aperture radar (SAR) and global positioning system data to invert for the coseismic fault slip of the 2016 Mw 6.6 Muji earthquake in western China. Our results indicate that the earthquake ruptured two asperities, which were separated by a ~ 10-km-long slip gap. InSAR observations (2014-2016) before the earthquake show two aseismic creeping sections along the Muji fault. The western creeping section overlapped with the coseismic slip gap, and the eastern creeping section marked the eastern termination of the earthquake rupture. The spatial coincidence of creep with coseismic slip gap suggests aseismic slip might arrest and act as a barrier to seismic rupture propagation. Moreover, we observe that the creep rate along the western creeping section was similar before and after (2017-2020) the earthquake, while it accelerated along the eastern creeping section after the earthquake. Creep rate acceleration along the eastern creeping section is likely to be promoted by positive Coulomb stress changes. InSAR time-series data show that the promotion has lasted several years and is perhaps long lasting, highlighting a need to reassess the aseismic slip behavior and seismic potential along creeping faults with large historical earthquakes.