中文摘要：

在现代地震较为平静的则木河断裂带中段,集中分布有一系列大型古滑坡,并具有高速、远程碎屑流等强动力特征,这些现象给人类进一步探索＂大规模滑坡事件＂提供了诸多思索和启发。以底古村附近﹑规模达3.7×10~8m^3的巨型古滑坡为研究对象,根据地质调查数据建立山体的岩体力学概念模型。运用具有模拟动力环境条件的离散元数值分析程序（UDEC）,探明山体失稳的临界动力条件为a=0.6 g,之后陆续增大地震加速度（a分别为0.8 g、1.0 g、1.2 g、1.4 g、1.6 g）,观察程序计算出不同加速度条件下的滑坡堆积状态可知,当a=1.6 g时滑坡堆积状态与当前地貌相符,进一步得出诱发山体发生高速远程碎屑流运动的初始加速度为a≥1.6 g（相当于Ⅺ度地震的动力强度）的基本结果。由此推论：该巨型滑坡事件是由强度超过Ⅺ度的地震所触发,近代地震活动极为平静的断裂带中段,历史上曾发生过Ⅺ度以上强烈地震。

英文摘要：

Large ancient landslides are found along the central segment of Zemuhe fault in Southwestern Sichuan of China, which concentrate at the part with relatively calm seismic activities in the modern history. Strong dynamic characteristics can be observed in the landsides, including high speed and long travel distance of the debris. It is postulated that these landslides may have been triggered by a violent prehistoric earthquake, or numerous strong seismic activities occurred in the middle of Zemuhe fault zones. The study aims at understanding the failure mecha- nism of Digu landslide and the simulation of its failure process based on the field investigation. The size of Digu landslide is estimated to be approximately 10 ~ 107 m3. Discrete element numerical analysis （UDEC） is applied to simulate the dynamic conditions and to analyze the critical dynamic condition that triggered the slope failure. The critical dynamic condition is achieved when the earthquake acceleration a≥ 1.6 g and seismic intensity of XI equiv- alently based on the results of the simulation, in which the failure modes are similar to the prototype. It is possible that the gigantic Digu landslides was triggered bystrong earthquake of with the earthquake intensity equal or greater than the level of XI occurred in the middle of Zemuhe fault zones in the past.