| The middle reaches of the Bailong River is a high-incidence area of geological disasters in China.Due to its unique topography and geological conditions,landslide disasters and debris flow disasters are frequent and large in scale,causing huge losses of people's lives and property,it will have a great impact on the sustainable social and economic development and ecological environment construction.Interferometric Synthetic Aperture Radar is favored by many scholars due to its large monitoring range,high accuracy,and weather resistance.It has been successfully applied to the field of geosciences with minor deformations such as landslide deformation and surface subsidence.The time-series InSAR technology is applied to the surface deformation monitoring in the middle reaches of the Bailong River,which overcomes the traditional limitations of low time resolution,low accuracy,and weather influences,and realizes a large-scale dynamic monitoring of surface deformation at a long distance.This paper takes the Zhouqu-Lianghekou section of the middle reaches of the Bailong River as the research area,uses Sentinel-1A lifting rail SLC data as the data source,and carries out surface deformation monitoring through SBAS-InSAR technology.Since the single-track InSAR result is the projection component of the true surface deformation vector in the line of sight direction of the radar,it often fails to reflect the true surface deformation.Therefore,based on the geometric information,slope and aspect of the lifting rail SAR data,and on the basis of the LOS deformation results of the lifting rail,the quasi-three-dimensional surface deformation field of the study area is constructed.On this basis,the temporal and spatial characteristics of surface deformation in the study area are analyzed.Based on the temporal and spatial characteristics of typical landslides as prior knowledge,potential landslides were identified in combination with the disaster-pregnancy background of the study area.The main results and conclusions are as follows:(1)Based on the LOS deformation results of the ascending and descending orbits obtained by the SBAS-InSAR technology,the quasi-three-dimensional surface deformation field of the study area is established.Based on the SBAS-InSAR technology,this paper obtains the surface deformation results of the ascending and descending orbits from Zhouqu to Lianghekou in the middle reaches of the Bailong River.The spatial distribution patterns of the surface deformations of the two orbits are the same.However,due to geometric differences,the deformation rate of the lifting rail on the same slope is positive and negative,and the same track on the two slopes with opposite east-west slopes also has opposite positive and negative deformation rates,which cannot reflect the true surface deformation..Therefore,combining the geometric information,slope and aspect of the elevator satellite sensor,and using previous algorithms,the quasi-three-dimensional surface deformation field of the study area is established,and the deformation rate values in the horizontal east-west,vertical and downslope directions are obtained.(2)The temporal and spatial characteristics of surface deformation in the study area are analyzed.The areas with larger deformation variables are mainly distributed on the slopes on both sides of the valley.The horizontal deformation is significantly larger than the vertical deformation.The subsidence area is mainly distributed on the valleys on both sides of the Minjiang River,showing a continuous distribution pattern.The vertical deformation of valleys on both sides of the Bailong River is relatively scattered.At the same time,it is found that there is a great correlation between the horizontal east-west deformation rate and the fault activity.It is speculated that the Pingding-Huama fault(strike-slip fault)is the main controlling factor for the horizontal deformation of the entire study area.Analysis of the time characteristics of surface deformation in the study area based on time series statistical analysis tools found that,except for noise points(or deformation rates and small points),the number of linear points is small,mainly distributed in areas far from the river valley;non-linear points are The valley slopes are more distributed,which is consistent with the characteristics of landslides developed along both sides of the valley in the region.The number of secondary deformation points is significantly more than bilinear and abrupt points.In particular,abrupt points can be used as one of the important signs of potential landslide identification.(3)The development process of Nanyu landslide and Yahuokou landslide were analyzed,and the early identification of potential landslides in the study area was carried out based on the disaster-pregnancy background of the study area.The Nanyu landslide and the Yahuokou landslide have similar development processes,both of which are cumulative processes of long-term surface deformation driven by rainfall,and the seasonal deformation curves of the two landslides conform to the general characteristics of landslide development.The study found that the potential landslides in the Zhouqu-Lianghekou section of the middle reaches of the Bailong River are mainly distributed in areas with a slope greater than 10°,and the lithology is mainly marl and phyllite,which are washed and eroded by rain all year round,and seasonal due to gravity.The stepped ground deformation caused the stability of the slope to be damaged,and finally a landslide occurred with the rainfall of a certain year.Based on the temporal and spatial characteristics of the surface deformation in the study area,this paper identified 27 potential landslides in combination with the slope and stratum lithology of the study area.Among them,the Zhongpai landslide and the Suoertou landslide have been extensively studied to show their hazards.Other potential landslides are also the conditions for the development of the above-mentioned landslides have been met,and sufficient attention should be paid. |
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