Assessment Of The Susceptibility Of Collapse And Landslide In The Wenchuan Earthquake Disaster Area

This paper takes the Wenchuan earthquake disaster area as the research area to analyze the spatial distribution of collapses and landslides in the disaster area.Based on fractal theory,quantify the contribution of environmental impact factors to the formation of collapse and landslide.And according to the variable-dimensional fractal results and the correlation of evaluation factors,the significant factors that affect the distribution of collapse and landslide are selected.Combined with GIS,a variety of evaluation models were used to study the susceptibility of collapse and landslide in the Wenchuan earthquake-stricken area,and the accuracy of the evaluation results of each model was compared.The main results and conclusions are as follows:(1)Based on the actually measured collapse and landslide database and multi-source spatial data information in the study area,the spatial distribution of collapse and landslide in the Wenchuan earthquake disaster area is explored.A total of 11 impact factors including PGA,elevation,slope,aspect,slope type,lithology,distance between faults,annual average rainfall,distance between water systems,distance between roads,and land use,are extracted.(2)Analyzing the relationship between the spatial distribution of collapse and landslides and the classification of each factor,the following conclusions are obtained: PGA>0.6,1100m-2000 m elevation section,slope>30°,east and southeast slope,convex slope,Wutai,Late Archean and Great Wall strata,fault distance <3km,water system distance <2km,rainfall 900-1100 mm section,road distance <2km section and forest land are the factors grading that are prone to collapse and landslide;The distribution density of collapse and landslide in the study area basically increases with the increase of PGA and slope,the decrease of fault distance,water system distance and road distance.(3)Based on fractal theory,analyze the fractal dimension characteristics of collapse and landslide distribution and evaluation factor classification.The results show that the distribution of collapses and landslides has variable-dimensional fractal characteristics with all 11 factors such as PGA,indicating that the spatial distribution of collapses and landslides is comprehensively affected by all factors.According to the cumulative sum order and the absolute value of the fractal dimension,the contribution of each factor to the distribution of collapse and landslide is obtained as: slope > fault distance > elevation > water system distance >slope direction > annual average rainfall > PGA > road distance> slope type > lithology > land use type.(4)Based on the level of influence of each factor on the distribution of collapses and landslides and the results of the independence test of each factor.Finally,A total of 9 impact factors including PGA,elevation,slope,aspect,slope type,lithology,distance between faults,annual average rainfall and distance between water systems are selected as the core factors for the evaluation of collapse and landslide susceptibility in the Wenchuan earthquake area.(5)Based on the collapse and landslide training samples,a total of 6 models of information volume(I),certainty coefficient(CF),weight of evidence(WOE),logistic regression(LR),information volume and logistic regression coupling(I-LR),and certainty coefficient and logistic regression coupling(CF-LR)were used to evaluate the susceptibility of collapse and landslides in the study area.(6)Based on the collapse and landslide verification samples,applying frequency ratio and ROC curve to measure the evaluation accuracy of each model.The AUC values of the six models are all greater than 0.88,indicating that all models have high accuracy.The I-LR model has the highest AUC value,reaching 0.907,and the evaluation result is the best.The accuracy comparison of the six models is: I-LR > CF-LR > LR > I > WOE > CF.Based on the optimal model I-LR,according to the natural breakpoint method,the research is divided into very low prone areas,low prone areas,medium prone areas,high prone areas,and extremely high prone areas.