Coseismic and Postseismic Deformation of the 2016 Mw 6.6 Aketao Earthquake from InSAR Observations and Modelling

On November 25, 2016, the Mw 6.6 Aketao earthquake occurred in Xinjiang, western China. We used the combination of ascending Sentinel-1A, descending Sentinel-1B and ascending ALOS-2 PALSAR data to measure the coseismic deformation. The line-of-sight (LOS) coseismic deformation implies that the earthquake was dominated by right-lateral strike-slip. Ignoring the fault-perpendicular deformation, the fault-parallel and up–down deformation was extracted based on the combination of Sentinel-1A and 1B observations. Results show that the maximum fault-parallel deformation is ~ 13.7 cm at the north wall and the minimum is ~ −16.5 cm at the south wall of the Muji fault. Then, coseismic slip distribution was derived using the steepest descent method (SDM) based on a single-segment fault model using the three InSAR LOS observations as constraints. The slip distribution reveals two slip centers. The maximum slip of the eastern center is 0.5 m at a depth of 8.8 km, where the rake angle is ~ 181.2°. The maximum slip of the western center is 0.6 m at a depth of 10.8 km, where the rake angle is ~ 181.1°. The derived seismic moment obtained equals the Mw 6.6 earthquake. In this study, postseismic deformation time series in 1.5 years after the earthquake were retrieved from 26 multi-temporal Sentinel-1 descending scenes. The postseismic LOS deformation at the north and south walls of Muji fault both increases with time but in opposite directions. The cumulative deformation is 60–80 mm at the north wall, and –30 to −20 mm at the south wall. The postseismic deformation shows similar patterns with the coseismic deformation, and has the same mechanism. There is no obvious lock at the unbroken gap.