Coseismic deformation and slip distribution of the 2017 Mw 6.3 Jinghe, Xinjiang, western China earthquake based on InSAR observations: a buried reverse event on previously unknown fault

Abstract

SUMMARY The 2017 Mw 6.3 Jinghe earthquake occurred in the orogenic zone of the North Tianshan mountain range, Xinjiang, western China. No evident surface rupture was identified by field investigation conducted immediately after the earthquake. We investigate the coseismic and post-seismic deformation fields due to the Jinghe event using the C-band Sentinel-1 SAR imagery, and further analyse its causative fault. The Generic Atmospheric Correction Online Service for InSAR (GACOS) model is employed to remove the atmospheric phase delay of multiple InSAR deformation maps. Coseismic deformation fields are resolved by averaging the high quality deformation maps. A nonlinear inversion scheme is used to find the optimized fault geometry in a layered elastic crust. The results imply that the Jinghe earthquake is characterized by thrust faulting, with striking and dipping angles of ∼62° and ∼28°, respectively. Subsequently coseismic slip distribution is estimated using the steepest descent method program, constrained by the derived coseismic deformation fields. The inversion results show that the average slip is ∼0.08 m and the average rake angle is ∼98°. The maximum slip is ∼0.24 m, located at the depth of 12.9 km. The moment magnitude is estimated to be Mw 6.38. The fault geometry is generally consistent with the relocated aftershocks distribution. Both the InSAR-derived deformation field and the aftershock distribution indicate that the Jinghe earthquake is attributed to a previously unknown buried fault beneath the Yongji fold with a strike of 62°. No significant post-seismic deformation is identified in the zone of coseismic deformation. This study shows that the Jinghe earthquake is a typical inland thrust event in the North Tianshan area, which is affected by south to north compression due to the Indian-Eurasian collision.