黄土地震滑坡运动特征研究——以海原特大地震诱发滑坡为例

Kinematic characteristics of loess seismic landslides:a case study of landslides triggered by the Haiyuan great earthquake

基于1920年海原81/2级特大地震诱发的568处典型黄土滑坡,从方向性特征、远程滑移特征以及流滑特征等3个方面探究黄土地震滑坡运动特征,主要结论如下:(1)海原地震诱发黄土滑坡主滑方向集中于60°~90°和270°~300°两个区间,与斜坡坡向优势范围50°~90°和255°~290°较为一致,体现出明显的顺坡向特征;(2)主滑方向与发震断裂走向平行或呈小角度相交(0°~30°)的滑坡占比41.9%,滑动方向受断层错动方向的影响较为显著;(3)滑坡密集分布于迎坡面,发育数量为背坡面的1.98倍,表现出典型的迎坡面特征;(4)滑坡最大水平距离与坡高的相关性明显,滑坡密集发育在坡高30~120 m的范围内,滑坡的等效摩擦系数均小于0.4,展现出典型的远程滑移特征;(5)568处滑坡中等效摩擦系数小于0.17的占比70.95%,表现出显著的流滑特征。作为黄土地震滑坡发育特征研究成果的重要补充,所得结论对深入开展黄土地震滑坡成灾机理与风险评估研究具有一定的参考价值。

Based on 568 typical loess landslides induced by the 1920 Haiyuan M_(S)81/2 earthquake,the study explores the kinematic characteristics of loess seismic landslides from three aspects:directivity,long run-out slip characteristics,and flow-slide characteristics.The main conclusions are as follows:(1)The main sliding directions of landslides induced by the Haiyuan earthquake are concentrated in two intervals:60°-90°and 270°-300°,which are consistent with the dominant slope direction ranges of 50°-90°and 255°-290°,respectively,demonstrating a distinct characteristic of being along the slope direction.(2)Landslides whose main sliding direction is parallel to or intersects with the strike of a seismogenic fault at a small angle(0°-30°)account for 41.9%,and the sliding direction is substantially affected by the fault dislocation direction.(3)Landslides are densely distributed on the facing slope,the number of which is 1.98 times that on the back slope,demonstrating typical facing slope characteristics.(4)A correlation exists between the maximum horizontal distance of a landslide and the slope height.Landslides are densely developed at a slope height of 30-120 m,and the equivalent friction coefficients of landslides are all less than 0.4,showing typical run-out slip characteristics.(5)Landslides with an equivalent friction coefficient of less than 0.17 account for 70.95%of the 568 landslides,revealing flow-slide characteristics.As an important supplement to the research results on the development characteristics of loess earthquake landslides,the conclusions have a certain reference value for further research on the disaster mechanism and risk assessment of loess earthquake landslides.