Risk assessment of secondary geological disasters induced by the Yushu earthquake

The Yushu Ms 7.1 earthquake occurred on April 14, 2010 in Qinghai Province, China. It induced a mass of secondary geological disasters, such as collapses, landslides, and debris flows. Risk assessment maps are important for geological disaster prevention and mitigation, and also can serve as a guide for post-earthquake reconstruction. Firstly, a hazard assessment index system of secondary geological disasters in the earthquake region was built in this paper, which was based on detailed analysis of environmental and triggering factors closely related to geological disasters in the study area. GIS technology was utilized to extract and analyze the assessment index. Hazard assessment maps of secondary geological disasters were obtained by spatial modeling and overlaying analysis. Secondly, an analysis of the vulnerability of hazard bearing bodies in the area was conducted, important information, such as, population density, percentage of arable land, industrial and agricultural outputs per unit area were regarded as assessment indices to evaluate socioeconomic vulnerability. Thirdly, the risk level of secondary geological disasters of the area was obtained by the formula: Risk=Hazard x Vulnerability. Risk assessment maps were categorized into four levels, including "low", "moderate", "high" and "very high". These results show that some urban areas are at very high risk, including Jiegu, Chengwen, Xiaxiula and Sahuteng towns. This research can provide some references and suggestions to improve decision-making support for emergency relief and post-earthquake reconstruction in the study area.