CHARACTERISTICS OF SECONDARY GEOLOGICAL HAZARDS INDUCED BY YILIANG 907 EARTHQUAKES IN YUNNAN PROVINCE

The MS5.7 earthquake occurred at 11:19 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 the Ⅷ and Ⅶ intensity areas respectively are 11 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.