Surface Deformation Monitoring Research Based On Time Series InSAR Technology

The surface deformation is caused by natural factors (such as earthquake, glacial drift) or human factors (groundwater extraction, coal mining, large-scale engineering construction, etc.) caused by the displacement of the surface elevation changes or phenomenon, when surface change variables beyond a certain limit will evolve into geological disasters, that brings serious damage to human life and property security. Lanzhou is located in the Qinghai-Tibet plateau and the loess plateau convergence zone, which have special geological condition and complex landform conditions. This paper expounded the significance of surface deformation monitoring and early identification for geological hazard. Monitoring the surface deformation effective in Lanzhou and surrounding areas, and finding the principal cause of surface deformation have an important meaning.Time series InSAR technique is developed nearly 10 years ago, which is a kind of surface deformation monitoring method aiming at the bottleneck problem of coherence loss because of long time interval, the spatial baseline and the atmospheric perturbation to interferometric phase. We selected the SBAS-InSAR technology to obtain the surface deformation of Lanzhou city. The surface deformation monitoring accuracy is greatly increased, which become the most efficient method of the surface deformation monitoring field. This paper based on ENVI SARscape platform and ENVISAT ASAR data, we did a lot of experiments on co-registration of master and slave images, choosing baseline and time interval threshold, calculated the surface deformation situation of Lanzhou city and the surrounding areas, got the following results.(1)As a kind of planar observation method based on microwave remote sensing, InSAR technique is introduced in order to verify the unique advantages and development potential of radar interferometry technique in the surface deformation monitoring.(2)For coherence average evaluation, we calculated coherence of different time interval and space baseline length conditions, analyzed the influence law of space-time baseline and time interval, preliminary built the mathematical model of the coherence estimation. The paper calculated different land types and vegetation samples, analyzed The distribution law of different land types and surface coverage coherence, at last the paper explored the influence of the surface characteristics influence to coherence;(3)Done experiments of the application of SBAS-InSAR technology, including image co-registration, interferogram filtering method selection, sensitive parameters choosing, the surface deformation information inversion etc. The whole technology process has been optimized, finally obtained the surface displacement of the city of Lanzhou, preliminary explored the feasibility of time series InSAR technology in surface deformation monitoring at the northwest covered by loess.(4)Analyzed the surface deformation in space and time distribution of Lanzhou, demonstrated the possible reasons for the deformation. The Fu Long-Ping, Dong gang-zhen, Sha Jing-yi and other typical regions displacement on the time series were analyzed, and provided a reliable basis for the prevention and control of geological disasters in Lanzhou area and city construction.