Fault Slip Inversion Of 2016 Menyuan Earthquake From InSAR Deformation Fields By Multi-orbit Sentinel-1A Images

InSAR?Interferometric Synthetic Aperture Radar?,is booming to the present as an Earth observation new technology.It has produced great impact on many research fields of earth sciences.One of the most successful applications of InSAR is to survey the deformation caused by earthquakes.However,one of its limitations is that an interferogram only measures one component of the surface deformation,that is the projection of the surface three-dimensional deformation in the LOS direction,has greatly limited the capability of In SAR technique in characterizing the true surface displacements.At present,one way to solute“LOS Amphibious”is using the two different LOS direction coseismic deformation fields of ascending-orbit and descending-orbit modes,to inverse the fault slip distribution.An Mw5.9 earthquake struck the Menyuan County,Qinghai Province on January21,2016.The shock did not rupture to the surface,which caused it controversial about confirmation of the causative fault.By using the high-resolution,continuous coverage,multi-angle InSAR observations from the descending and ascending Sentinel-1A data,the causative fault and its geometry is determined by optimizing the inversion of the slip distribution.Those inversions provide an insight into the pattern of stress distribution of the crustal deformation in the northeastern margin of the Tibetan Plateau,and will be of benefit to studying the long-term earthquake hazard in this region.The main results and conclusions are as follows:?1?We processed the descending and ascending Sentinel-1A data by“two-orbit”D-In SAR technology and acquired surface deformation fields of the Menyuan earthquake.The results show the deformation occurred mainly in the south wall of fault,where uplift deformation is dominant.The uplift deformation is significantly larger than the subsidence and the maximum uplift for ascending and descending track in the LOS is 6cm,8cm respectively.?2?Based on the Okada Model,we inverted jointly the ascending and descending data for the fault slip distribution and source parameters by constructing different fault models with different dip angles.The optimal inverted result is that the dip is 43°,the strike is 128°with the mean rake of 85°.The maximum slip is about 0.27m.The inverted seismic moment M0 is 1.13×10¹⁸N·m,and the moment magnitude Mw is 5.9.?3?By making a comprehensive analysis of the focal mechanism,fine positioning aftershocks and regional tectonics,a conclusion is drawn that the causative fault for the Menyuan earthquake might be the Minyue-Damaying fault which dip to south-west,and the fault movement is dominated by the thrust with a small component of dextral strike-slip.