鲁甸地震的滑坡物质运移规律与地形特征

长期、缓慢的地貌演化具有阶段性的特点,构造抬升与侵蚀相互作用引起山坡物质运移,使地貌单元具有向相对稳定状态转变的趋势.滑坡作为山坡物质运移的一种主要方式,在地貌演化过程中起到了重要作用.2014年鲁甸MS6.5地震诱发了异常多的滑坡,可以看作是该区地貌物质在短时间内发生的集中调整过程.这些滑坡主要沿河流分布,表明河流侵...

STUDY ON THE DISTRIBUTION OF CO-SEISMIC LANDSLIDES AND TERRAIN FEATURES IN THE MS6.5 LUDIAN EARTHQUAKE AFFECTED AREA

The 2014 Ludian,Yunnan MS6.5 earthquake triggered an unusually large number of co-seismic landslides compared with other events of similar magnitudes in southwestern China.We use landslidearea ratios(LAR)based on a grid(cell size≈1 km2)to delineate the specific distribution of landslides rather than the averaging landslide density that is commonly employed.Results show that the distribution of co-seismic landslides triggered by the 2014 Ludian MW6.5 earthquake contains LAR values ranging from less than 1.0%to 36.1%with the high values concentrating in river valleys of the study area.Then we examine the correlation between some topographic parameters and the co-seismic landslides in each grid cell and especially focus on the grids with larger LAR(>10%).In addition to examining the correlation between the elevation,local relief and average slope angle(S),we propose a notion of the expected slope degree(ES)to further analyze the correlation between these co-seismic landslides and local topographic features.The expected slope degree can be calculated by dividing the local relief(the difference between the maximum and minimum elevation)by cell length for each grid cell,which is a kind of smooth of the local terrain instead of the average slope.After this procedure,we make a regression analysis on the expected slope degrees and the average slope degrees for all grid cells.Finally,we choose those cells that deviate from the regression line as the unstable units and examine their relation with landslide distribution.Results show that the elevation has a negative relationship with both the average slope degrees and the local relief in the study area,which can be classified as a kind of negative topography implying strong river erosion on the landform.In general,there exists a good positive linear correlation between expected slope degrees and average slope degree for the study area.While larger LAR values(LAR≥10%)lie at the sites that deviate from the regression line,likely representing unstable slopes prone to landsliding.Moreover,it is found that most of these sites with high LAR are just located along river valleys,which permits to predict that mass wasting by future earthquakes or other factors will recur at these places.As a contrast,the analysis results of topographic parameters in the Jiuzhaigou earthquake affected area show different characteristics.Thus,the understanding of the relationship between the geomorphic features and the spatial distribution and scale of landslides is helpful to improve the accuracy of prediction on earthquake-induced landslides and to identify potential large-scale landslides in the early stage.