汶川地震触发崩塌滑坡"背坡面效应"及其动力学机理

The "back slope effect" of earthquake-triggering landslides refers to the phenomenon that the number of landslides in the slopes opposing to the moving direction of seismic wave is obviously higher than in the slopes facing the seismic wave. Such effect is a type of " topographic amplification effect". Many landslides triggered by earthquake in history displayed evident "back slope effect", but their studies were limited to the description of this phenomenon and the hypothesis on its reasons . What needs further study is the formation conditions and kinetic mechanism. The landslides triggered by Wenchuan Earthquake showed "back slope effect" strikingly,which is worth deep research. This project is intended to study the landslides triggered by earthake referring to the theory of seismic wave propagation and basic rules on dynamic response of slope. Based on establishing the conceptual model of " back slope effect",field investigation and high resolution remote-sensing interpretation are carried out to discover the typographic and geologic coupling conditions resulting in " back slope effect". Futhermore, experimental means such as seismic monitoring is utilized to set up the geomechanic model of " back slope effect" so as to reveal its kinetic mechanism. The abovementioned study may improve the scientific understanding on the earthquake triggering mechansim of landslides and thus provide theoretic support for the susceptibility analysis of earthquake-triggering landslides , risk assessment and management so as to guide the route selection of linear projects such as building of road and railway in the rural areas of high earthquake risk as well as hazard prevention and reduction in cities and towns.

地震触发崩塌滑坡的"背坡面效应"是指背向地震波传播方向斜坡上的崩塌滑坡要显著多于迎波坡面的现象，属于地震波"地形放大效应"的一种。历史上多次地震都表现出了明显的"背坡面效应"，但对其研究仅限于现象描述和成因假设，其产生条件和动力学机理有待深入研究。初步研究表明,汶川地震滑坡的"背坡面效应"较显著，为其深入研究提供了难得机会。本项申请以汶川地震触发崩塌滑坡为研究对象，依托地震波传播理论和斜坡动力响应基本规律，在建立"背坡面效应"概念模型的基础上，通过现场调查、高精度遥感解译和GIS统计分析，查明产生"背坡面效应"的地形、地质条件；进而结合地震动监测和理论分析等手段，揭示其动力学机理。上述研究，有望提高对强震触发崩塌滑坡机理的科学认识，为地震崩塌滑坡易发分区、危险范围预测、风险防范提供理论支撑，对高地震风险山区公路、铁路等线性工程的选线以及城镇地质灾害防灾减灾具有重要的指导意义。

地震触发崩塌滑坡的“背坡面效应”是指背向地震波传播方向斜坡上的崩塌滑坡要显著多于迎波坡面的现象，属于地震波“地形放大效应”的一种。历史上多次地震都表现出了明显的“背坡面效应”，但对其研究仅限于现象描述和成因假设，其产生条件和动力学机理有待深入研究。本研究以汶川地震触发崩塌滑坡为研究对象，依托地震波传播理论和斜坡动力响应基本规律，在建立“背坡面效应”概念模型的基础上，通过现场调查、高精度遥感解译和GIS统计分析，查明了产生“背坡面效应”的地形条件为（1）“背坡面效应”显著区斜坡的走向近垂直或平行于发震断裂，（2）陡峭而单薄的山体较平坦宽厚的山体更容易产生“背坡面效应”；进而结合地震动监测、数值模拟和理论分析等手段，揭示了其动力学机理，当振动波垂直入射到背波坡面时，将产生全反射，在陡峭而单薄的山体内，入射波和反射波相叠加，使坡面处的振动加强，使崩塌滑坡更容易发生。本研究成果为地震崩塌滑坡易发分区、危险范围预测、风险防范提供了理论支撑，对高地震风险山区公路、铁路等线性工程的选线以及城镇地质灾害防灾减灾具有重要的指导意义。