InSAR Extraction Of Seismic Deformation Field And Inversion Of Fault Slip Distribution Considering Atmospheric Effect

The destructive power of earthquake disaster is very strong,which has brought great losses to all parts of the world.InSAR technology can carry out large-scale observation on the surface,and has inherent advantages in seismic deformation monitoring.However,in the process of InSAR imaging,it is inevitably affected by the environment or its own systematic error,which reduces the monitoring accuracy of InSAR technology.Studies have confirmed that among many influencing factors,the influence of atmospheric delay effect is particularly prominent.Therefore,in order to suppress the influence of atmospheric delay effect on the extraction accuracy of seismic deformation field,the improved iterative tropospheric decomposition method is used to correct the atmospheric delay of the obtained coseismic interferogram in order to reduce the interference of atmospheric effect.Based on the corrected coseismic deformation field data,the nonlinear Bayesian algorithm is used to obtain the optimal geometric parameters of the fault,and then the EI curve method considering the model error is used to inverse the fault slip distribution,and the fine slip distribution results of the fault are obtained.The main research contents are as follows:(1)Removal of tropospheric delay effect in InSARWhen the iterative tropospheric decomposition method is used for atmospheric delay phase correction,the inverse distance interpolation method is generally used to determine the turbulence component,but this method does not fully consider the influence of elevation change on the estimation results when estimating the turbulence component,resulting in the inaccurate estimation of turbulence component,which affects the effect of tropospheric delay estimation.Therefore,this paper proposes an improved inverse distance weighted interpolation tropospheric decomposition optimization model to improve the accuracy of turbulence component delay estimation,and then realize the purpose of tropospheric atmospheric delay phase correction.In order to verify the effectiveness of the optimization model,taking Jiashi earthquake on January 19,2020 and Yangbi earthquake on May 21,2021 as examples,the iterative tropospheric decomposition optimization model were used to correct the tropospheric delay of the obtained coseismic differential interferogram.The results show that the atmospheric effect in the interferograms of Jiashi earthquake and Yangbi earthquake can be effectively removed.The average deformation monitoring accuracy of Jiashi earthquake’s ascending and descending orbit were increased by 37.3% and 9.8% respectively,and the average deformation monitoring accuracy of Yangbi earthquake’s ascending and descending orbit were increased by 14.3% and 11.1% respectively.After atmospheric correction,the deformation range and the value of near-field deformation can be determined more clearly.(2)InSAR extraction of coseismic deformation field and inversion of fault slip distribution in typical seismic areasThe selection of smoothing factor value plays a key role in fault slip distribution.Accurate smoothing factor value will greatly improve the accuracy of slip distribution inversion.Relevant research shows that the L-curve method is commonly used to select the smoothing factor value,but this method depends too much on the data fitting accuracy,and there is a convergence problem in the calculation.Therefore,a fault fine slip distribution inversion method based on EI curve method considering model error is proposed in this paper.Firstly,the optimal geometric parameters of fault are obtained based on nonlinear Bayesian algorithm,then the optimal value of smoothing factor is selected by EI curve method considering model error,and finally the optimal value of smoothing factor is used for fine slip distribution inversion in SDM fault slip distribution inversion.In order to verify the effectiveness of this method,based on the atmospheric delay correction of Jiashi earthquake and Yangbi earthquake,this paper carries out the inversion of fault fine slip distribution by EI curve method considering the model error.The results show that for Jiashi earthquake,the optimal smoothing factor is0.06,and the optimal fault model parameters are: strike 274 87 °,dip angle 20 °,average slip angle 90.59 °,moment magnitude is Mw6 06。At the same time,the inversion results show that Jiashi earthquake is a typical thrust fracture event with a small amount of strike slip component.For Yangbi earthquake,the optimal smoothing factor value is 0.08,and the inversion results show that the strike of the fault is 310.80 °,the dip angle is 89.00 °,the average slip angle is172.42 °,the moment magnitude is Mw 6.13。 At the same time,the fault slip model shows that the Yangbi earthquake is a strike slip fracture event caused by NW trending dextral strike slip fault.