中文摘要：

大型高位地震滑坡因其瞬时破坏性及灾害链效应而备受关注。通过对1786年磨西73/4级地震触发的泸定烂田湾滑坡深入详细的调查及根据邻近摩岗岭地震动监测成果,分析了滑坡的形成机制,并利用三维离散元模拟软件—3DEC,模拟了滑坡的运动过程。研究揭示,地震波在经过地形及背坡效应放大后,斜坡滑源区地震峰值加速度超过1 g,地震作用首先在强卸荷斜坡后缘沿陡倾坡外的结构面拉裂并向下贯通,随着地震力的持续作用,拉裂面外侧的岩体沿缓倾结构面剪断滑出,因此烂田湾地震滑坡形成机制为拉裂-滑移。滑坡的演化过程为：孕育-启动→高位高速运动→碎屑流→堆积堵江4个阶段。滑坡堵江后形成堰塞湖并在短期内决口。

英文摘要：

Largescale high landslides triggered by earthquake are concerned for its instantaneous destructive and disaster-chain effect. Through field investigation on the Lantianwan landslide occurred during 1786 Moxi Earth- 3 quake （M =7 3/4） at Luding,Sichuan, China, this ＇paper reveals its formation mechanism and simulates its movement by 3 Dimensional Distinct Element Code. After seismic wave was amplified through topography and back-slope effects, the seismic peak ground acceleration on the source area of the declivity can exceed 1 g. Seismic action firstly led to tensile failure and down along steep oblique external structural planes on the back of the strong unloading slope. With continuous action of seismic force, the rock mass in the outside pull-apart plane was cut and thrown out along the gently dipping structural planes, so the genetic mechanism of the Lantianwan landslide is tension-cracking and horizontal sliding. The evolution of the landslide can be divided into the following four stages ： （a） the embryonic and starting stage ; （b） the high-position and high-speed motion stage ; （c） the debris flow stage ; and （d） the accumulation and river stoppage stage. There was a barrier lake after the river stoppage and it burst in a short time.