InSAR 3D Coseismic And Postseismic Deformation Of Maduo Mw7.4 And Inversion Of Fault Slip Distribution

The Bayanhar block on the north-central Tibetan plateau and its surrounding areas have strong tectonic stress and deformation,which is the most active area of earthquakes in China.For the interior of Bayanhar block,there are few previous studies on fault tectonic stress and seismogenic environment.The 2021 Mw7.4 Maduo(Qinghai,China)earthquake is the only large-scale earthquake in recent years,which fills the gap of large-scale earthquakes above M7+ in Bayanhar block.Therefore,it has important research value for further exploring the stress development,fault tectonic activity and seismogenic environment in Bayanhar block.In this paper,the 2021 Mw7.4Maduo earthquake as the research object,the coseismic and postseismic characteristics are studied.In terms of coseismic research,firstly,coseismic deformation fields in LOS direction and azimuth direction are obtained separately based on D-InSAR and POT in the ascending and descending orbits.Then,the three-dimensional coseismic deformation field of the higher accurate is solved by using SM-VCE algorithm.Then,the geometric parameters of seismogenic fault are obtained by the nonlinear inversion method based on Levenberg Marquardt minimization algorithm,which is used as the prior information of linear inversion.Finally,the SDM is used to linearly invert the fine slip distribution of seismogenic faults constrained by three-dimensional coseismic deformation field.In terms of postseismic research,the time series deformation results of the Mw7.4 Maduo earthquake are obtained based on SBAS-InSAR,and the kinematics mechanism of postseismic deformation is analyzed.The main conclusions are as follows:Coseismic research:(1)Based on the coseismic deformation map which are obtained by D-InSAR and POT in the ascending and descending orbits,found that the seismogenic fault may have geometric changes such as fault bending.The fault trace shows that the approximate strike of seismogenic fault is 282°.The upper and lower parts of the fault trace of the coseismic deformation field on the ascending and descending orbits show inconsistency,which may indicate that the deformation movement is dominated by the horizontal deformation and is generated by the strike-slip movement of the seismogenic fault.(2)Based on the analysis of three-dimensional coseismic deformation field with higher accuracy constructed by SM-VCE algorithm,it is found that the Mw7.4 Maduo earthquake is dominated by left-lateral strike-slip motion,and the deformation is mainly contributed by the horizontal displacement components of E-W and N-S.Meanwhile,the deformation distribution appears multiple bends in space with the fault trace,which means that the fault stress may be released at the bend,and it also indicates that the lower part of the seismogenic fault may break and there may be fault segmentation.(3)The fine slip distribution of seismogenic fault based on the SDM linear inversion shows that the seismogenic fault shows obvious left-lateral strike-slip motion characteristics.Along the fault,four large convex sliding sources are unevenly distributed in the shallow crust,which are mainly concentrated in the depth ?6 km,and the coseismic sliding is mainly limited to the depth range of 0-15 km.Along the seismogenic fault,the strike dip angle and strike have changed,with dip angles of 72.7°,78.9°,80.6° and 84.0° respectively.Postseismic research:The postseismic time series deformation results are obtained based on SBASInSAR.The result shows that there is obvious shallow slip in the early stage after the earthquake.The postseismic afterslip mainly occurs in the velocity-strengthening layer around the fault trace area,and the occurrence of postseismic shallow slip is largely the result of the gradual release of postseismic afterslip stress driven by stress.At the same time,the inferred shallow coseismic slip deficit may be caused at least in part by the velocity-strengthening conditions above the seismogenic layer.