The Susceptibility Analysis Of Landslides Triggered By The 2014 Ludian Earthquake

China is located between the Circum-Pacific seismic belt and Alpine-Humalayanseismic zone,and is one of the countries with the most serious earthquake disasters in the global continent.Landslide is among the most common secondary disasters caused by earthquake.It is the phenomenon of rock or soil sliding caused by seismic vibration.Landslide disaster triggered by earthquake has characteristics which is large range,wide distribution and strong disaster-causing capacity.The damage and loss caused by landslide triggered by earthquake will exceed earthquake itself sometimes and bring great disaster to the safety of people life and property.It is great significant to acquire database of landslide triggered by earthquake,comprehend spatial distribution of co-seismic landslides and divide the vulnerable areas of landslides occurring in future for post-earthquake relief,reconstruction and geological hazard prevention.Large earthquakes in mountainous areas often induce landslides,which always lead to serious disasters.As of 15 August 2014,at 15:00(Beijing time),a Mw 6.2(Ms 6.5)earthquake occurred in Ludian County,Zhaotong City,Yunnan Province of China617 people were killed,112 were missing,3143 were injured,229,700 were emergency relocated and 80,900 houses collapsed because of thisearthquake.Because the steep terrain,high topographic relief,and fragile geological conditions in the quake affected area,the earthquake triggered a large number of landslides and caused serious personnel and property losses.In order to obtain complete and detailed database of co-seismic landslides,spatial distribution of landslide and vulnerable area of co-seismic landslide,in this paper,the three aspects have been in intensive research.Of this study(1)had established the inventory of landslides triggered by Yunnan Ludian earthquake base on interpreted pre-and post-earthquake high-resolution remote sensing images provided by Google Earth platform,and the accuracy and integrity of inventory obtained in this study were verified by comparing with previous research and co-seismic landslides inventories of other earthquakes occurred in mountainous areas with similar magnitudes;(2)Terrain factors(gradient,slope aspect),geological factor(lithology),and seismic factor(seismic intensity,distance from epicenter)were selected as co-seismic landslide impact factors,landslide number,landslide area,landslide number density and landslide area density were selected as evaluation indexes,statistical relationship between impact factors and evaluation was obtained to discuss spatial distribution of co-seismic landslide of Ludian earthquake;(3)Gradient and lithology were selected as represent of co-seismic impact factors,landslide number density was regard as evaluation index to discuss the relationship between represent factor and other factors with influence to ability of triggering landslides;(4)Based on information value model,the vulnerable area of co-seismic landslides in study area was divided obtaining vulnerability map,and the accuracy of this model was tested.The main conclusions of this study are as follows:(1)Ludian earthquake triggered at least 12,817 co-seismic landslides in about603km~2 study area with a density of 21.25/km~2,landslide area is 16.33km~2 and area density is 2.71%.(2)The inventory of landslides triggered by Ludian earthquake obtained by this study is the most complete and detailed at present thorough comparing with previous study and co-seismic landslides inventories of other similar magnitude in mountainous areas earthquakes.(3)The co-seismic landslides occurred mostly at places with slope angle of 10°-40°and the susceptibility of landslides increases with the slope angle;Affected by the propagation direction of the earthquake rupture,the eastward-facing slopes are more prone to slide;The differences between the landslide susceptibility and landslide scale in different strata indicate that lithology is also a control factor,the vulnerable strata of co-seismic landslides are P1 and Z1,the strata of Z1 where large-scale co-seismic landslides are common;The vulnerability of landslides decreases with the decrease of seismic intensity.(4)Distribution area within seismic intensity ranks can influence ability of part of gradient triggering landslide,some level of gradient of triggering landslide ability is affected by slope aspect and lithology distribution;Part of lithology of triggering co-seismic landslides is affected by gradient distribution,is not affected by slope aspect,the relationship between distance from epicenter and intensity are not to be determined due to missing of strata distribution.(5)The calculation results of information value of each impact factor verify the results of co-seismic landslides spatial distribution.(6)The most widely distribution of vulnerability in the study area was low grade;Co-seismic landslides are mainly distributed within extremely high and high vulnerability grades;The area with high grade of landslides vulnerability presents NW-SE trending,mainly distributed in steep valley;Areas with very low vulnerability are mainly located far from the epicenter;The distribution of vulnerability is closely related to the distribution of gradient and seismic intensity.(7)The accuracy of information value model is 0.85,and the accuracy is good.