Research On Application Of DInSAR And PS-InSAR Deformation Measurement

Both natural factors and human activities are responsible for the serious cause of geological disasters,thereby threatening safety of people’s lives and property by destroying a good livable environment.In the process of such a serious geological disaster,the corresponding surface deformation often occurs.Therefore,it is very important to monitor the surface deformation to predict the occurrence of disasters,understand the disaster process and reduce the disaster caused losses.Interferometric synthetic aperture radar(InSAR)is a new space geodetic technology,which can image the surface deformation with high resolution and wide coverage.In this dissertation,the traditional differential InSAR(DInSAR)is used to study the coseismic deformation of the Yutian Mw6.3 earthquake in 2020,and the land subsidence in the Fuyang area in recent three years is studied by using the the time series interferometric synthetic aperture radar(TS-InSAR)based on permanent scatterers.The specific research ideas and results obtained are as follows:(1)The DInSAR method was used to obtain the coseismic deformation field of the 2020 Mw6.3 Yutian earthquake,and to study the seismic deformation source.The noise level in the deformation signal is filtered by the interferogram stacking,and a high-quality coseismic deformation field is obtained;the quadtree down-sampling method is used,to sample the deformation field.Results can reflect the characteristics and redundancy of the deformation field for the subsequent deformation inversion work.On this basis,this paper first uses the geodetic Bayesian inversion algorithm to invert the deformation field of the 2020 Yutian earthquake,and obtain the optimal source parameters.The inversion results indicate that the strike and dip of the fault is 187.8 degrees and 60.1 degrees,respectively.The dimension of the rupture area is 11.32 km long and 5.24 km wide.The ruptured fault is buried at 2.49 km deep.Based on these inferred source parameters,we constructed a fault plane in uniform elastic half space,16 km long and 12 km wide,and used the gradient descent method to invert the coseismic deformation field again,and obtained the slip distribution on the fault plane and the three-dimensional surface displacement field.The slip distribution and the three-dimensional displacement field show that the rupture of this earthquake is mainly normal faulting;the hanging wall of the fault shows subsidence with a maximum subsidence of 18.11 cm;the footwall of the fault shows uplift with a maximum uplift of 5.49 cm.The slip distribution is concentrated within a depth of 4 to 9 kilometers,and the maximum amount of slip is at a depth of 6.5 kilometers.The geodetic moment is 3.18×1018 N·m,which is equivalent to an Mw 6.3 earthquake.The seismogenic fault may be a branch fault at the southwest end of Altyn Tagh Fault zone in the Gongga Co fault zone,(2)In this paper,the permanent scatterer-InSAR(Permanent Scatterer-InSAR,PS-InSAR)method is used to study the land subsidence in Fuyang area.From July 2017 to October 2020(nearly three years),106 SAR images were divided into three groups for time series InSAR analysis,and we obtained the average deformation rate map of the area.The results show that there are varying degrees of land subsidence in Fuyang and surrounding cities;the maximum average subsidence rate in Fuyang City can reach 35 mm/yr;in the surrounding rural areas,there is a slight uplift of the ground,with an average rate close to 5 mm/yr.In order to verify the reliability of the PS-InSAR method,we used the SAR image of October 18,2019 as the main image and the SAR image of October 24,2020 as the slave image,and used the DInSAR method to generate a one-year span surface deformation field.We converted it into a vertical deformation map.By comparing the results obtained by two different methods,we found that the results of the PS-InSAR method are reliable.Because Fuyang area is located in northern Anhui,rainfall is low,and deep groundwater has been exploited for a long time.Urban areas are densely populated,a large amount of groundwater is pumped and regional surface water replenishment is low,resulting in a decrease in the water content of the cohesive soil layer and consolidation and settlement.In rural areas,groundwater is extracted to irrigate crops,and the groundwater can be partially recharged by surface water,and there is almost no ground subsidence.Therefore,in Fuyang,urban and rural areas have inconsistent land subsidence.