The Study On InSAR Geological Hazard Monitoring In Southwest Alpine And Canyon Areas

Landslide,as a kind of geological disaster,has been concerned because of its characteristics such as fast occurrence speed,wide area involved and great economic loss.On October 11,2018,the Baige landslide in Tibet Autonomous Region shocked the whole country.When the landslide occurred,solid particles on the surface of the earth poured down the slope,blocking the main flow of the Jinsha River below the landslide,forming a barrier lake and causing direct economic losses of 7.4 billion yuan.Generally speaking,most landslides have to undergo a slow development process before approaching the sliding node,except for the instantaneous sliding of rainfall-type landslides.Therefore,it is very important to monitor and track the development stage of landslide by various methods for the prevention and control of geological disasters.The mountainous areas in southwest China are covered with dense vegetation,gully crisscrossed,abundant rainfall,and distributed between "two mountains sandwiched by a river",which is a typical alpine canyon landform.Geological disasters such as landslides occur frequently due to the large elevation difference,relief of topography,complex climatic environment,and human engineering activities.Synthetic Aperture Radar(InSAR),a new kind of earth observation technology,has been widely used in the field of landslide monitoring for its characteristics of wide coverage,high monitoring accuracy and no weather influence.InSAR technology has many limitations when it is applied to geological disaster monitoring in alpine and canyon areas due to its special topography.Based on this,this paper takes the landslide area of Guxue Township,Derong County,Sichuan Province,and Zhuangfang landslide of Liuku Town,Lushui City,Yunnan Province as examples to discuss the core problems faced by InSAR technology when it is applied to alpine and canyon areas and the corresponding measures.The specific contents are as follows:(1)The effects of geometric distortion,interference incoherence,atmospheric delay error and line-of-sight deformation limitation on InSAR disaster identification in alpine canyon region were analyzed.The geometric distortion region of the study area is calculated by using visibility and sensitivity analysis,so as to avoid the misjudgment of regional deformation caused by the geometric distortion of image.The causes of interference incoherence are explored from the perspective of registration error,vegetation cover and large gradient of deformation,and some suggestions are put forward.Based on the characteristics of vertical stratification and turbulence disturbance,some suggestions and methods are proposed to reduce the influence of atmospheric delay error.The linear deformation decomposition of monorail and the joint two-dimensional solution of lifting rail are used to solve the limitation problem of linear deformation.(2)The SBAS-InSAR technique was used to monitor the deformation in the landslide area of Guxue Township,Derong County,Sichuan Province,and the differences of the monitoring results of the lift rail deformation were analyzed from the perspectives of visibility,sensitivity and coherence.Combined with the rainfall data,the deformation time series of the descending orbit is extracted to analyze the internal relationship between them.Finally,the lineof-sight deformation of the landslide area is obtained using Stacking-InSAR technology,and it is geometrically decomposed into east-west and vertical two-dimensional angles to quantitatively investigate the landslide evolution process.(3)Based on the ALOS-2 data and Sentinel-1A data,the deformation of Zhuangfang landslide in Liuku Town,Lushui City,Yunnan Province was carefully monitored.The deformation time series and section line were extracted from the ALOS-2 monitoring results to analyze the deformation distribution characteristics of the whole landslide surface.The Sentinel-1A lifting rail deformation was combined to solve the two-dimensional deformation,and the landslide development law was analyzed qualitatively and quantitatively from the vertical and east-west deformation results.