A Study On Hazard Assessment And Optimization Of Regional Loess Landslide Based On Statistical Models

Loess Plateau is one of the important areas with high hazard of geological disasters in China.With the development of western China and the deepening of new-type urbanization,the risk situation of regional landslide disaster is becoming increasingly severe.Therefore,it is urgent to strengthen the risk management strategy of geological disaster.As a key step of risk assessment,landslide quantitative hazard assessment has gradually become a research hotspot,and it is also an inevitable choice to improve the scientificity and reliability of risk management.To crack the technical bottlenecks and operational difficulties we faced in geological hazard survey and assessment,we focus on the Loess Plateau,Shatang River basin in Qinghai and Min county earthquake disaster area,the hazard assessment methods with good performance based on statistical analysis model were selected.From various dimension,such as the different disaster geological background,space scale,index system and assessment methods,landslides expressions and scales,a series of assessment scenario comparison and optimization research are carried out,and the initial results and understanding are shown as follows:(1)The landslide database of the Loess Plateau was preliminarily established,and the distribution rules of landslides were summarized.There are 7271 landslide(points)in Loess Plateau.Landslides are mainly distributed in the southwest,south and east of the Loess Plateau,while rarely develop in the northwest.Moreover,the development of loess landslide is closely related to relief,river,active fault and so on.There were 875 landslides(polygon)in the Shatang River basin in Qinghai,with a total area of about 65.24km2.The degree of landslide development gradually increased towards the downstream of the river.Most landslides distributed in the branches of Shatang River are more than them distributed in the main river.There are 6478 earthquake landslides(polygon)at the earthquake disaster area in Min county,with a total area of about 1.76km2.There are mostly small landslides,mainly distributed in the sides of the Tao River and the seismogenic fault.(2)The landslide hazard assessment methods based on statistical analysis model were compared and optimized.Through the hazard assessment of Loess Plateau and Shatang River basin,the principle and assessment performance of information(IV)model and logical regression(LR)model were compared and analyzed,and an optimized information-logistic regression(IL)hybrid model was proposed.The comparison of the success rate of 3 models shows that the IL model performs best,followed by IV model and LR model.The success rate results are,Loess Plateau:76.0%(IL model)>69.2%(IV model)>65.9%(LR model);Shatang River basin:79.2%(IL model)>73.3%(IV model)>71.7%(LR model).(3)The differences of the landslide hazard assessment based on different models in different scales were revealed.The landslide hazard assessment and comparison in large,medium and small scale based on 3 models were carried out based on the results of the landslide inventory results in Shatang River basin.The comparison of landslide hazard assessment in different scale based on the same model(ILmodel)shows that small landslide hazard assessment had the best performance.The success rates were:82.1%(small)>77.0%(whole)>75.1%(medium)>74.5%(large).The comparison of landslide hazard assessment based on different models in the same scale(small)shows that the IL model has the best performance.The success rates were:82.1%(IL model)>76.2%(IV model)>74.4%(LR model).(4)The establishment of characteristic index and elaborate index in different spatial scales and geological background conditions were explored.Due to the difference of the data accuracy and the key point of assessment,other than the basic disaster background such as geological structure and topography,some characteristic index are to be considered,like the geomorphologic partition,specific probability PGA of the Loess Plateau,the landslide strength probability of Shatang River basin,the Arias intensity considered the effect of terrain in Min county earthquake area,etc.The comparison of Min county earthquake landslide hazard assessment based on IL model shows that the success rate that considers the effect of ground motion terrain is significantly better(87.9%>83.1%),which reflect the effectiveness of the detailed index to the special topic.In conclusion,the results could provide technical method references and problem solutions for quantitative hazard assessment and survey of geological hazards in the Loess Plateau in different scenario conditions.