| Hundreds of thousands or even tens of thousands of landslides will be triggered when an earthquake occurs in mountainous areas.Among many secondary disasters such as tsunamis,ground fissures,earthquake liquefaction and earthquake landslides,earthquake landslides are more harmful,and the losses caused are often greater than the earthquake disaster itself.Our country is one of the countries with the most serious earthquake disasters.Among them,the1970 Tonghai earthquake of Ms7.7 in Yunnan triggered a large number of coseismic landslides,causing serious casualties and property losses.But so far,there are few studies on the landslide triggered by this earthquake,and the study of the earthquake landslide in this big earthquake is of great significance to the earthquake landslide zoning and disaster prevention and mitigation in the Qujiang fault zone.This paper takes the Tonghai earthquake high-intensity area(Ⅷ-X)as the research area.By comparing the satellite images before and after the earthquake,and using the method of artificial visual interpretation,the landslide is objectively and accurately delineated,and the Tonghai earthquake landslide inventory is established.Combined with topography,geology,earthquake and other controlling factors,the spatial distribution law of earthquake landslides is analyzed.Using the sampling method of Bayesian thought,based on the logistic regression model,the probability of earthquake landslide occurrence in the study area was calculated.And based on this model,taking the peak ground acceleration(PGA)as the trigger factor,the probability of earthquake landslide occurrence under different PGA(0.1-1.0g)in the Qujiang fault area was obtained.The main results achieved are as follows:(1)Preprocessing such as image cropping and georeferencing of historical satellite images(Keyhole satellite images)before and after the earthquake,and comparing the color tone and shape of the images before and after the earthquake.In the study area,640 coseismic landslides were obtained through interpretation,and a seismic landslide database in the high-intensity area of the Tonghai earthquake was established.The total area of landslides is 3.01km~2,mainly distributed on both sides of the Qujiang River Valley,and also on both sides of the seismogenic fault-Qujiang fault zone.(2)Select ten influencing factors including elevation,slope angle,slope aspect,slope position,the distance to the river,the distance to the seismogenic fault,strata,the distance to the epicenter,seismic intensity and PGA,and use the Landslide Number(LN),Landslide Area(LA),Landslide Number Density(LND)and Landslide Area Percentage(LAP)are the four landslide abundance indicators.The relationship between coseismic landslides and various influencing factors is analyzed,and the spatial distribution law of coseismic landslides in the Tonghai earthquake is obtained.By comparing and analyzing the law of coseismic landslides with typical strong earthquakes,it is concluded that the coseismic landslides of the Tonghai earthquake mainly have the characteristics of“small number,small and medium scale,and small influence range”.(3)Using the sampling method of Bayesian thinking,randomly select sample points in the study area,100 points per 1km~2,and a total of 259,400 sample points are randomly generated,of which the landslide sample points fall into the landslide surface area,and the rest is a non-landslide sample point.Based on the logistic regression model,the landslide risk assessment in the study area was carried out,and the receiver operating characteristic curve(ROC)test was carried out,where the area under the ROC curve(AUC)was 0.814,and the model accuracy higher.Based on this model,with PGA as the trigger factor,the occurrence probability of earthquake landslides under different PGAs(0.1-1.0g)in the Qujiang fault area was obtained,and the landslide risk zoning map in the Qujiang fault zone was drawn.Figure[44]Table[7]Reference[94]... |
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