关键词: 地貌演化, 滑坡, 相关性分析, 期望坡度, 鲁甸地震

Abstract: The 2014 Ludian, Yunnan M_S6.5 earthquake triggered an unusually large number of co-seismic landslides compared with other events of similar magnitudes in southwestern China. We use landslide-area ratios(LAR)based on a grid(cell size ≈1km²)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 M_W6.5 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.landscape evolution, landslides, adaptive adjustment, expected slope, the Ludian earthquake