Slip Model for the 25 November 2016 Mw 6.6 Aketao Earthquake, Western China, Revealed by Sentinel-1 and ALOS-2 Observations

Abstract

On 25 November 2016 (UTC 14:24:30), an Mw 6.6 dextral strike-slip earthquake ruptured Aketao county in the northwestern portion of the Kongur Shan extensional system, western China. We extracted surface deformation maps and investigated the distribution of the coseismic slip of the 2016 Aketao earthquake by exploiting the Interferometric Synthetic Aperture Radar data imaged by the Sentinel-1 satellites of the European Space Agency and the ALOS-2 satellite of the Japanese Aerospace Exploration Agency. Assuming the crust of the earth is an elastic half-space homogeneous medium, the best fitting slip model suggests a dip angle of 78° for the seismogenic fault. The rupture of the 2016 Aketao earthquake may have consisted of two sub-events that occurred in rapid succession within a few seconds, resulting in two large discrete asperities with maximum slip of ~0.85 m, which were separated by a ~6 km-wide small slip gap. The maximum slip for the sub-event near the epicenter was mainly concentrated at a depth of ~10 km and that of the other at a depth of ~5 km. The estimated total seismic moment from the optimal slip model is 1.58 × 1019 N•m, corresponding to an event with a moment magnitude of 6.74. More than 65% of the aftershocks occurred in the areas of increased Coulomb failure stress, in which the stress was estimated to have been increased by at least 0.1 bar. Matching the potential barrier on the fault with the depth distribution of aftershocks implies that friction on the causative fault was heterogeneous, which may play a primary role in controlling the active behavior of the Muji fault.

Keywords

• radar interferometry
• Pamir
• Aketao earthquake
• rate- and state-dependent friction
• seismic risk