汶川大型地震滑坡的类型及启程剧动机理研究

2008年汶川大地震诱发大型地震滑坡300余处,造成了巨大的生命财产损失,研究其发生机理有重要的理论意义和防灾减灾的实用价值.经收集分析已有地震滑坡的研究成果及多次深入现场调查,本文发现众多大型地震滑坡发生时都伴随有区别于汶川主震的地面震动,并将其称为滑坡地面震动,简称滑坡震动.本文在论述滑坡震动依据、成因及特征的基础上,根据滑坡震动力与主震力的组合情况及其对大型地震滑坡的影响不同,将汶川地震滑坡划分为3种类型:主震型地震滑坡,迟震型地震滑坡和同震型地震滑坡.认为主震型地震滑坡在主震结束前滑动,其主导失稳力学因素为主震力和重力,无滑坡震动或可忽略; 同震型地震滑坡亦在主震结束前滑动,但其主导失稳力学因素除主震力和重力外,滑坡震动力起重要作用; 迟震型地震滑坡在主震结束后滑动,主导失稳力学因素为滑坡震动力和重力.认为大型地震滑坡地面震动的发生与活断层导致地震类似,据此提出了滑坡震动加速度的估算方法,并以此为基础分析研究了各类型地震滑坡的启程剧动机理.

CLASSIFICATION AND SUDDEN INITIATION MECHANISM OF LARGE LANDSLIDES TRIGGERED BY 2008 WENCHUAN EARTHQUAKE

2008 Wenchuan earthquake triggered more than 300 large landslides followed by huge loss of life and property, which emphasizes that study on their forming mechanism has a great significance in theory and practical application for disaster prevention and mitigation. By field investigation and analysis on published material about the landslides, a new term landslide-quake is defined in this paper. It is different from Whenchuan mainshock by its effect on the forming of the landslides. This paper looks into the evidences, formations and characteristics of landslide-quake. It gives different combinations of landslide-quake and earthquake. It finds that these large landslides triggered by 2008 Wenchuan earthquake can be classified into the following three types.(1)Normal earthquake landslide, for which no landslide-quake occurs and the main contributing forces are earthquake force and the gravity of sliding mass.(2)During earthquake landslide, for which a landslide-quake generates during the earthquake and the main contributing forces are landslide-quake force, earthquake force and the gravity of sliding mass.(3)After-earthquake landslide, for which a landslide-quake generates after the earthquake and the main contributing forces are landslide-quake force and the gravity of sliding mass. The opinion is suggested that the process of large landslide generation is similar to the sudden cut of a seismic fault and the estimation of the magnitude of a landslide-quake and the provided shearing force. Based on the above, the processes of the sudden initiations of these three kinds of landslides are analyzed. The concept of landslide-quake is a new explanation for the mechanism of sudden initiation of a large rapid landslide, and it, along with the other results of this study, provides a reference for large rapid landslide research.