Analysis Of Surface Deformation In A Landslide-Prone Heifangtai Area,Gansu Using InSAR Technology And Muti-temporal Datasets

Globally,many people are injured or killed each year in geological disasters.The annual economic losses caused by landslides exceed billions of dollars.In China,more than 50% of the geological and secondary disasters are caused by a landslide.Unfortunately,most landslide-prone areas are unmonitored or previously unknown.Therefore,monitoring potential landslide areas are imperative.The surface deformation assessment is an effective means of monitoring landslide events.Interferometric Synthetic Aperture Radar(InSAR)technology is widely used in surface deformation monitoring because it can monitor small surface deformation in the centimeter or even millimeter range on a wide spatial extent with the short time,low cost,and high level of precision.Therefore,this thesis mainly uses a time-series InSAR(the Small Baseline Subset InSAR)technique to carry out ground monitoring and analysis on the Heifangtai,Gansu Province,China where frequent landslide events occurred.The surface deformation results of Heifangtai,Gansu Province from October 2014 to September 2017 were evaluated.The surface of the slope of the edge of Heifangtai was extremely unstable during the three years,and the maximum deformation rate reached 20.8 mm/year.The area with a deformation rate less than –5.6 mm/year was called the potential landslide area.In comparison with the location map of the landslides drawn by in situ observations of others' studies,most of the potential landslide areas of the Heifangtai have experienced landslide events.Thus,the SBAS-InSAR technology was able to detect potential landslide areas and could be an effective approach to provide information supporting the local landslide warning system.Compared with the other six landslide groups in Heifangtai,the number of landslides and deformation rate of the Dangchuan landslide group were the most.To study the characteristics on the surface deformation and trigger mechanism of landslides in different seasons,the SBAS-InSAR technique and the Sentinel-1A ascending and descending orbit datasets were used to analyze the surface deformation of Dangchuan 2,Dangchuan 3 and Dangchuan 4 regions in Heifangtai.The deformation results of the three regions before the landslide were as follows: the three regions have obvious displacement,the displacement direction was negative(away from the radar line of sight),and the displacement was greater than 20 mm,or even greater than 30 mm.Analysis of the relationship between precipitation,temperature,and Sentinel-1A GRD data and the absolute value of the surface deformation increments of the three regions was as the followings.The landslide occurred in Dangchuan 2 area on 29 April 2015,was related to the precipitation.The landslide occurred in Dangchuan 3 area on 29 February 2017,was related to the temperature variation(freezing and thawing of soil).The landslide occurred on 1 October 2017,in Dangchuan 4 area was affected by the precipitation,temperature variation and soil moisture.Therefore,the use of time-series InSAR technique and multitemporal SAR data can predict landslide events,and to some extent,can analyze the causes of landslide disasters.