Coseismic Deformation and Fault Inversion of the 2017 Jiuzhaigou Ms 7.0 Earthquake: Constraints from Steerable Pyramid and InSAR Observations

The 8 August 2017 Ms 7.0 Jiuzhaigou earthquake was generated in the transition zone between the Tazang fault, Huya fault, and Minjiang fault, all being part of the East Kunlun fault system. In this study, two pairs of SAR (synthetic aperture radar) data from Sentinel-1 satellite were used to derive the surface displacement observations along the satellite line-of-sight (LOS) directions using the differential interferometric SAR (D-InSAR) method. A steerable pyramid filtering method (i.e., a method for a linear multiscale, multidirectional decomposition and filtering technology) was proposed to optimize and enhance the geological features from interferometric image and coseismic deformation field. The 3D deformation was derived under the constraint of the combined D-InSAR and MAI method. The small baseline subset InSAR (SBAS-InSAR) time series method was used to obtain the cumulative deformation across the fault system. Fault slip inversion results from interferogram of InSAR indicate that the 2017 Jiuzhaigou earthquake was dominated by left-lateral slip, the surface movement was dominated by horizontal deformation, the vertical deformation was small, and the coseismic deformation variable in the east–west direction was the largest, with a maximum deformation of 0.2 m to the east and 0.14 m to the west. The maximum slip is about 77 cm, which is located at a depth of 9 km. The moment magnitude obtained by inversion is Mw 6.6, and the seismic fault is the Huya fault