Hazard Evaluation of Secondary Geological Disaster Based on GIS and Information Value Method

5·12 Wenchuan earthquake triggered a series of secondary landslides, landslides, debris flows, and other geological disasters, which posed a major threat to peoples' lives and property and socio-economic development. For risk assessment of secondary geological hazards in the area, the worst-hit Wenchuan County was selected as the study area. Remote sensing and geographic information technology spatial data management and spatial data analysis platform have been applied to gain relevant information, to make a correlative analysis between secondary geological disasters in the study area and the topography, lithology, hydrology, earthquake rupture. In addition, information value method has been used to evaluate the risk of secondary geological disasters. It is found that the area of high risk, moderate risk and low risk is 1 130.196 km², 1 739.584 km², 1 213.219 km² respectively. The distribution of secondary geology disaster triggered by earthquake has the colony type distribution characteristic featured with a concentrated development of geological disasters in the fault zone and the nearby regions and a quick decay and the fragmentary distribution farther away form the fault zone areas. Analysis also shows that risk of secondary geological disaster in north and east areas of Wenchuan is heavy, while that in the west and south areas is light, which is coincident with the reality. The study further demonstrates that the geographical information system combined with information value model can quickly and effectively evaluate the spatial distribution and risk of secondary geological disasters.