| Under the influence of basic geographical environmental factors such as fragile geological environment,huge topographical undulations,complex stratum lithology,etc.,the surface deformation of Jiuzhaigou area is active.In addition,affected by strong geological tectonic movement,rainfall and other factors,various geological disasters in this area have long been prone to occur,occur repeatedly,and occur with high frequency.Due to the special topography and geological conditions and abundant vegetation coverage in the study area,geological disasters are highly concealed.In the process of disaster prevention and control,it is difficult to make early predictions.Therefore,it is extremely easy to cause huge social and economic losses and casualties.Jiuzhaigou has been listed as an important monitoring area for surface deformation in Sichuan Province.How to effectively identify and prevent potential geological disasters in this area has become the focus of this article.When monitoring deformation in mountainous areas,traditional methods of investigating geological hazards are often less adaptable,and the accuracy of detection results is limited.In recent years,Synthetic Aperture Radar Interferometry(InSAR)technique has shown unparalleled advantages in surface deformation monitoring.It can carry out the imaging work of the observed area all time,all-weather,and on a large scale.Moreover,it has the advantages of fast,accurate and low cost in the process of detecting the microdeformation of the earth.InSAR technique can provide data and technical support for the subsequent identification of potential geological hazards and the task of geological hazard risk zoning.In this paper,the ALOS-2 SAR image is selected as the research data.InSAR technique is applied to the detection of surface deformation.Then,based on the results of the previous surface deformation monitoring,the potential geological hazards in the study area were extracted.And expound the development law and influencing factors of geological disasters.Finally,the improved analytic hierarchy process-information model is used for geological hazard risk assessment in the study area.The main research content and achievements of this paper are as follows:(1)The experimental data of this study selected 15 L-band ALOS-2 ascending orbit images in Jiuzhaigou County.D-InSAR and SBAS-InSAR techniques are used to monitor the surface deformation.Using GIS spatial analysis methods and visual interpretation methods,261 potential geological hazards are screened out.The results of time series deformation analysis of potential geological disasters show that the surface deformation in the study area is in an overall stable and partially active state.And through field surveys,it was verified that more than 65% of the deformation interpretation areas had signs of deformation.The survey results show that InSAR technique is reliable for early identification of geological disasters.(2)In this study,the study on the spatial distribution characteristics,developmental causes and inducing mechanism of the hidden danger points of geological disasters is carried out.The results show that the development of geological disasters in the study area is affected by multiple factors such as topography and geomorphology,geological environment,climate and hydrology,and human activities.Then,this study selects 11 factors such as stratum lithology,slope,and rivers as evaluation factors to construct an evaluation index system for the susceptibility of geological disasters.(3)The weighted information model is used to assess the risk of geological disasters in the study area,and the analytic hierarchy process is used for weighting.To improve the traditional analytic hierarchy process,three methods of geometric average method,arithmetic average method and eigenvector method are used to calculate the weight.Replace the result of a single weight calculation with the average of these three values.The potential geological hazard points are used as the research layer and each evaluation factor layer is superimposed.And the improved AHP-information model is used to calculate the total information of each evaluation unit in the research area.Finally,the study area is divided into four areas: low-risk area,medium-risk area,high-risk area,and extremely high-risk area.And verify its evaluation accuracy by ROC curve.It can be seen that the area under the curve for success rates is increased from 0.812 to 0.854.The evaluation results show that the improved model improves the confidence of the prediction,and the improved method is effective. |
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