Surface Deformation Monitoring Research Of Danjiangkou Dam Area Based On InSAR Technology

Danjiangkou Reservoir is the main water source for the middle route of South-to-North Water Transfer Project,and its geographical location is extremely important.The Danjiangkou Dam is the core hub of the reservoir and deformation will inevitably occur in its long-term use.If the surface deformation of the dam and dam area cannot be discovered in time,it may cause catastrophic accidents,leading to major casualties,environmental damage and economic losses.Therefore,the effective monitoring for the deformation of the dam and dam area,the analysis for main inducements of deformation,the summaries for the distribution of deformation in time and space,are of great significance for the early prevention and control of Danjiangkou dam and dam area.However,the traditional ground monitoring method can only obtain the deformation information in a small range,and the space coverage obtained by these methods is discrete in results.Meanwhile,the deformation of the continuous region cannot be obtained.For some areas with poor natural conditions and being difficult to reach,it is impossible to arrange ground monitoring points,which directly leads to obstacles in obtaining ground deformation monitoring data in these areas.Interferometric Synthetic Aperture Radar(InSAR)technology can process efficient wide-area deformation measurement,which has the advantages of wide-range,low-cost,high-precision,and no affection by night and weather.It can monitor without ground monitoring sites and in the areas where man is difficult to reach.Furthermore,it can make up the shortcomings of traditional monitoring methods.Theoretically,InSAR can achieve millimeter or even higher accuracy in surface deformation monitoring.Therefore,synthetic aperture radar interferometry has become an important means in the field of ground monitoring,and it is powerful in surface deformation monitoring.Due to its strong advantages and development potential in surface deformation monitoring,InSAR technology has been widely used.In previous studies on factors leading to surface deformation,the influence of the area around the deformation area was often neglected,which would lead to incomplete analysis results.Therefore,this paper bases on the Single Look Complex(SLC)data product of interferometry Wide(IW)mode of the Sentinel-1A satellite,adopting the Differential interferometry(Differential InSAR,D-InSAR)technology and combining with Okada model theory which is important for analyzing the causes and mechanisms of seismic deformation,to study the influence of transient deformation caused by earthquakes around the dam area on the dam area.And study the influence of large-scale slow surface deformation around the dam area on the dam area by using the Small Baseline Subset InSAR(SBAS-InSAR)technique.The main work of this paper is given as follows:1.The development status of InSAR technology and its main applications in surface monitoring are studied.The development history of InSAR,D-InSAR and SBAS-InSAR technology in the field of ground measurement technology is carding.The principle of InSAR technology in the direction of ground mapping and the background and technical principle of D-InSAR technology monitoring surface deformation are sorted out.On the basis above,the main data processing flow of SBAS-InSAR technology in the slow surface deformation measurement in a large area is summarized.The conclusions show that the application potential of InSAR technology in surface deformation monitoring is huge.2.The D-InSAR technique and the Okada model are used to comprehensively invert the deformation of the dam area.By investigating the environmental background data of the seismic deformation locations around the dam area,this paper takes the xichuan that occurred 4.3-magnitude earthquake on 9 February 2018 as an example,using two Sentinel-1A satellite images covering the post-earthquake area of the target earthquake,based on the combination of D-InSAR technology and Okada model,this paper ues the least squares method to solve the fault geometry parameters,and linearly inverts the deformation condition of the earthquake occurrence area.The seismic parameters results of the model inversion are consistent with the results published by the seismic organization,indicating that it is feasible to use D-InSAR technology and Okada model to obtain seismic deformation.3.A remote sensing monitoring method for large-scale surface deformation based on step-by-step analysis is proposed.By summarizing the hydrological and geological data of dam area,the Sentinel-1A satellite SAR images which were acquired from 25 March 2017 to 19 March 2018 were used as experimental data,this paper bases on SBAS-InSAR technology,processing the image sets covering the Danjiangkou dam area with image registration,interference pairs selection,interferogram generation,phase unwrapping,orbit refinement and reflatten,average deformation rate estimation,etc,investigating the surface deformation in a large-scale research area,which is centered on the Danjiangkou dam area.This paper obtains the deformation information results of the research area,and analyzes the operation status of the Danjiangkou dam and the stability of the dam area.In order to further verify the effectiveness of the proposed method,this paper analyzes the results based on local topography and site hydrological data.The results show that the method used in this paper can effectively obtain a wide range of surface deformation information,and provide technical support for surface deformation monitoring in Danjiangkou dam area.