| In China,the mountain area accounts for more than 2/3 of total land area,and the frequency and scale of geological disasters such as landslides and mudslides are significantly higher than the world average level.Landslide disasters have high randomness,difficult prediction,and strong destructive power,which are harmful to life safety and infrastructure safety.A variety of technical means have played an active role in the field of landslide hazard research and achieved many reliable results.However,the situation that “the monitiored landslide does not occure but the occureed one does not measured” has repeatedly appeared,causing great trouble to the geological disaster workers.InSAR(Interferometric Synthetic Aperture Radar)technology,which has emerged in recent years,is widely used in landslides,earthquakes,land subsidence,etc.and monitor the surface micro-deformation caused by disasters,due to its advantages of large spatial coverage,low monitoring cost and little weather impact.This paper takes the Zhouqu-Wudu-Wenxian section of the Bailong River basin with high landslide hazard as the key research area,starting from the surface deformation,uses PS-InSAR and SBAS-InSAR methods to carry out large-scale deformation analysis and early identification of potential landslides on the basin scale during 2014-2018.Based on the large-area surface deformation data obtained by InSAR technology,the distribution pattern and time series variation of surface deformation in Bailong River Basin are analyzed,and the response relationship between surface deformation and fault structure and regional precipitation is explored.The ground deformation data obtained by InSAR technology are compared and verified by using the measured data such as surface displacement,earth pressure and water pressure of the ground monitoring station in the field.Using GIS spatial analysis method and PS-Time time series statistical tool,the PS(Permanent Scatters)points with different deformation intervals and different deformation trends are separated,and the early identification rules for landslides based on the combination of surface deformation,deformation trend and visual interpretation is established.The PS points for potential landslide identification are selected according to the identification rules,and the potential landslide border is delineated.The reliability and validity of the recognition results are verified by the field investigation,and the early identification of potential landslides is realized.conclusion as below:(1)The overall characteristics of surface deformation in the Bailong River Basin presents sinking in the valley and uplifting in the mountain.The valley deformation is dominated by the negative deformation away from the radar line of sight,and the southern mountain is significantly more than the northern mountain.The high mountainous area far from the valley is dominated by the positive deformation near the radar line of sight.The comparison of surface displacement,earth pressure and water pressure on the ground actual monitoring points proves that the surface deformation results obtained by InSAR technology are effective and reliable,and can reflect a wide range of surface deformation.(2)The results of InSAR calculations show that there is a certain response relationship between deformation and structurer,the same as rainfall.The section line analysis shows that the maximum positive deformation is in the high mountainous area above 2500 m,and the maximum negative deformation is in the valley area of 300 m above sea level.The closer distance from the fault,the larger negative deformation,and the farther away from the fault,the larger positive deformation.A positive deformation peak occurs in the region of 19 km away from the fault,and a negative deformation peak appears in the nearest region far from 300 m of the fault.It shows that the fault zone has a strong control effect on surface deformation,meanwhile,the rainfall and surface deformation curves of the rainfall monitoring station show that when heavy rainfall or continuous rainfall occurs,the morphological variables around the rainfall station are accelerated to decrease or rise.After the peak of rainfall at the monitoring station,the surface deformation has a displacement change of about 8-20 mm,which proves that rainfall is one of the induced factors of surface deformation.(3)According to the early identification rules of potential landslides established in the paper,105 potential landslides were successfully identified,of which 87 landslides coincided with the detected landslides,18 were newly discovered potential landslides,and 603 potential landslides have been detected in the field by the national land department.Compared with its results,there is a certain difference in the number of identifications,but the recognition accuracy is higher.The objective conditions of high vegetation coverage and complex atmospheric environment in the alpine valley area of the Bailong River Basin restrict the effective identification of PS points by InSAR technology to obtain higher density.At the same time,it should be noted that InSAR technology has obvious advantages of low cost,large range and short cycle compared to landslide detection.(4)The deformation results and distribution characteristics of PS-InSAR and SBAS-InSAR in the whole study area are consistent,and the spatial pattern of sinking and alpine uplift is found.The deformation trend has both linear and nonlinear changes.The overall change is mostly linear.The PS points obtained by the two methods have different densities,and the relative deformation intervals are also different.The former obtains a lower point density,and the latter has a higher point density.The average rate of positive deformation of PS-InSAR is concentrated at 4-9 mm/a,and the average rate of negative deformation is concentrated at-4-11 mm/a.The average rate of positive deformation of SBAS-InSAR is concentrated at 13-28 mm/a,and the average rate of negative deformation is concentrated at-15--33 mm/a.It shows that SBAS-InSAR has higher applicability than PS-InSAR in the deformation monitoring of mountain area with high vegetation coverage such as the Bailong River basin. |
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