云南彝良9·07地震次生地质灾害特征分析

摘要

The MS5.7 earthquake occurred at 1 1:19 on September 7,2012 in Yiliang county,Yunnan province, China.Later,a MS5.6 earthquake occurred again at 12:16.Many geological hazards were induced by the two earthquakes.They include collapses, landslides, mudslides and other secondary geological hazards.Field investigations show the following major characteristics of the secondary geological hazards of the Yiliang earthquakes.The number of secondary geological hazards was increased significantly after the earthquakes.The distribution of geological hazards that induced directly by the earthquake is controlled obviously by distance to the epicenter.The geological hazards densities at theⅧandⅦintensity areas respectively are 1 1 and 4.5 times of that at the Ⅵ intensity area.The distribution of geological hazards clearly shows the effect of hanging and foot walls of the geological fault.The seismic geological hazards density of the fault hanging wall is 2.6~3.9 times as that of the foot wall.The distribution of new secondary geological hazards is obviously controlled by the properties of rock types after earthquake.The effect is obviously that the “superposition of rainfall”and the “geological hazards chain”of secondary geological hazards after earthquakes.The main characteristics are “small magnitude with large disaster and more hazards with small scale”in Yiliang earthquakes.%2012年9月7日11时19分40秒，云南省彝良县发生M5.7级地震，12时16分29秒，再次发生M5.6级地震，两次地震诱发了大量的崩塌、滑坡、泥石流等次生地质灾害。通过现场调查，分析了本次地震次生地质灾害的主要特征：震后次生地质灾害数量明显增加、由地震直接诱发的地质灾害分布明显受震中控制；Ⅷ度区、Ⅶ度区的地震地质灾害点密度分别是Ⅵ度区地震地质灾害点密度的11倍与4.5倍；地质灾害的分布表现出很明显的“上/下盘效应”，上盘地质灾害密度是下盘地质灾害密度的2.6～3.9倍；震后新增次生地质灾害点的分布受岩土体性质控制明显；震后次生地质灾害“降雨叠加效应”与“链生效应”较为明显，具有“震级小、灾情大、灾害多、规模小”的特点。