Post-earthquake Secondary Geological Hazards Risk Assessment Based On Three-dimensional Image Data

Secondary geological disasters in the earthquake are caused by seismic activity geological disasters. Geological disasters increased earthquake damage effect, increasing the extent of earthquake damage, therefore the risk of secondary geological disasters is an important part of earthquake disaster situation evaluation. It has played an important role in the scope of the geological hazard prediction, geological disaster loss of pre-assessment and evaluation of geological disaster prevention project. Application of remote sensing technology to carry out investigation and assessment of geological hazards is essential, as it can throughout the whole process of investigation and assessment of geological hazards, monitoring and early warning, disaster assessment and disaster prevention, which is the inevitable trend of the development of modern high technology.5·12 Wenchuan earthquake formed a series of secondary landslide, landslides, debris flows, and other mountainous geological disasters. It is a serious threat to peoples'lives and property and socio-economic development. For risk assessment of secondary geological hazards, this paper selected the worst-hit Wenchuan County as the study area, Explores the Combination of GIS technology and methods of evaluation the amount of information theory and its application in risk assessment of geological hazards in Wenchuan County, the specific implementation process, using three-dimensional remote sensing technology and geographical information technology, spatial data management and spatial data analysis platform, extract the secondary geological disaster-induced factors, and its secondary geological disasters with the correlation of the quantitative comments, and then use the amount of information model, the risk of secondary geological disasters and their spatial distribution to predict and positioning. Main research contents are as follows:(1)Chapter one provides a short view of several spatial information technologies applications on landslide field,such as remote sensing,GIS,digital elevation model. Described the application status and prospects of three-dimensional remote sensing technology. Discussed the GIS/RS with the technical support of geological disasters in the reservoir area of regional landslide hazard assessment focused on the evaluation of content and a reasonable model for the focus of this paper pointed out the direction, planning to study the main content and hope to solve the problem.(2) Key remote sensing technique was explained in detailes for collapse, landslide and debris flow geological hazard research. The data sources selection, the spectral image correction, geometric correction and ortho-correction, three-dimensional model establishment of remote sensing were introduced. Remote sensing image processing research methods have raised aim at different research object, different degrees, different research phase of geological hazard.(3) By using IKNOS and QuickBird satellite image multi-temporal, high-resolution to analyse of the formation conditions of landslide, growth characteristics, deformation indications and major disaster situation. Three-dimensional remote sensing technology was applied to extract geological hazards information in the secondary geological disasters and high precision three-dimensional remote sensing model of landslide region was established. A set of practical and effective method of producing three-dimensional remote sensing images was put forward based on the traditional method of three-dimensional image produced, which improve the production effect and level of three-dimensional remote sensing images, enhancing the practicality of large-scale three-dimensional remote sensing images.(4) By using ETM combined with SPOT images of the study to extracted pregnant conditions for disaster, development status collapse, landslide and debris flow geological hazards and evaluation of distribution of geological disasters. Combined with the causes and behavior characteristics of collapse, landslide and debris flow geological hazards to modify and improve the interpretation of geological hazards identification signs and interpretation methods.(5)Induced factors of secondary geological disasters were extracted based on the advantage of remote sensing technique. Analysis of correlative character between secondary geological disasters in the study area and the topography, lithology, hydrology, earthquake rupture, and use information value method to evaluate the risk of secondary geological disasters. The area of high risk, moderate risk and light risk is 1130.196 km2,1739.584km2,1213.219km2 respectively; The distribution of secondary geology disaster triggered by earthquake has the colony type distribution characteristic, namely the fault zone,both sides of water and the nearby regions to focus development of geological disasters, but far away form the fault zone area geology disaster quickly decay and assumes the fragmentary distribution; Analysis from the regional character of disaster devilment shows that risk of secondary geological disaster in north and east area were heavy, west and south were light. The research results inosculate preferably with the fact. So geographical information systems combined with information value model can be quickly and effectively evaluate the spatial distribution and risk of secondary geological disasters.Studies have shown that, according to the existing landslide priori knowledge to remote sensing data, regional geological survey data as a landslide factor data source, with part of the field survey data, large and medium-scale fast regional landslide risk assessment is feasible. As space technology and the rapid development of computer technology, high-resolution, radar, hyperspectral remote sensing, digital automatic altimeter, the use of remote sensing data can be provided for regional landslide research much richer type information features in the image. Combination of ground engineering geology, indoor laboratory test data of small-scale geological hazard assessment is feasible, remote sensing technology in geological hazards research needs further widened.