A NE-Trending Oblique-Slip Fault Responsible for the 2016 Zaduo Earthquake (Qinghai, China) Revealed by InSAR Data

Abstract

Twelve Sentinel-1 images are used to measure the surface displacements caused by the Zaduo earthquake on 17 October 2016 in Qinghai, China. Comprehensive analysis of the local geologic structure, focal mechanisms, relocated aftershocks, and fault geometrical parameters from nonlinear inversions of the InSAR data indicates that a NE-trending fault with a strike of ~ 61°, namely the Aduo fault, was responsible for this event. Further geodetic inversions for finite fault models show that the dip angle of this fault is 75° to the SE. The majority of the slip occurred at the depth from 5 km to 17 km, and the normal-slip component was comparable to the strike-slip component. The peak slip of ~ 31 cm occurred at a depth of ~ 10 km. The InSAR determined moment is 9.61 × 1017 N m with a rigidity of 30 GPa, equivalent to Mw 5.9. The geological map reveals that the Aduo fault was characterized by a left-lateral strike-slip component in the past, as evidenced by the offset of Paleogene sedimentary rocks. Our results for the Zaduo earthquake suggest that the Qiangtang block probably consists of two or more sub-blocks with different eastward extrusion velocities and that the deformation of the Qiangtang block is occurring not only along its boundaries but also in its interior.