4·20芦山Ms7.0级地震地质灾害特征

为了揭示芦山7.0级地震次生山地灾害发育规律,结合遥感解译,震后第一时间对芦山震区开展了应急调查和危险性分析等工作.芦山7.0级地震诱发的地震地质灾害以小型崩塌为主,崩塌主要沿双石-大川断裂带,北西向几个深切峡谷段,如S210芦山-宝兴峡谷,芦山-双石峡谷,芦山-太平峡谷发育,其中震中附近的宝盛、太平及龙门崩塌密度最大.崩塌源主要分布在陡立谷坡中上部、突出山嘴等部位,堆积以块石、孤石及碎石为主,对灾区的公路破坏大,其次是坡脚的民房,并在今后一段时间内,威胁公路的正常运行.潜在不稳定斜坡和土质小型滑坡,由于沟道物源的增加,震后泥石流灾害链不可忽视.地震波强度及地形放大效应是控制灾害发育的主因,斜坡结构及风化也有重要的控制作用. 

Characteristics of Co-seismic Landslides Triggered by the Lushan Ms7.0 Earthquake on the 20th of April,Sichuan Province,China

In order to reveal the distribution laws of the secondary geohazards during the Lushan Ms7.0 earthquake, field investigations and interpretation of aerial photos after the earthquake were carried out to analyze the risk of the co-seismic geohazards. The results show that rockfall was the main type of the co-seismic geohazards. The rockfalls were mainly small-scaled ones and distributed along the area of the Shuangshi-Dachuan fault zone and the NW-strike gorges, such as the Lushan-Baoxing gorge, Lushan-Shuangshi gorge, and Lushan-Taiping gorge, in which the rockfalls occurred most densely in the area near the epicenter, such as Taiping, Baosheng, and Longmen. The source areas of rockfalls in the cross section of the valleys were mainly located at the middle and upper parts of a hill slope and the spur of a hill. The accumulation was mainly composed of blocks and gravel, which buried the roads, became a great risk to vehicles and houses at the toe of slopes, and would threaten the normal operation of the road in the near future. As the potential unstable slopes and small slides increase the source in the valleys and ramp during the earthquake, the debris flow would happen frequently. The PGA (peak ground acceleration) magnitude and topographic amplification was the main reason of the geohazards, and the slope structures and weathering was the second factor.