| The earthquake induced the secondary geological disasters such as large-scale mountain collapse, landslides and debris flows and other in earthquake zone, caused houses to collapse, and severely damaged infrastructure. However, it also cause a great loss to people’s lives and property. The Secondary Geological Disasters referred to geological disasters caused by the earthquake activity. Earthquake Secondary Geological Disasters enhanced the destructive effect of earthquake disaster, exacerbated the extent of earthquake damage. So it is an important part of research of the earthquake disaster. The Wenchuan earthquake in 2008 caused the landscape change of large areas, induced a large number of secondary geological disasters. They were collapses, landslides and debris flows. In these secondary geological disasters, the active period of landslide would last 5 to 10 years, and debris flow’s active period would last 10 to 20 years. Therefore, the monitoring of collapse, landslide geological disasters in Wenchuan earthquake zone, controlling the evolution characteristics of the geological disasters development, and making scientific prediction in time, is particularly important for the prevention of the geological disasters and local people’s life safety and economic development. The 3S(RS, GIS, GPS) technologies which based on remote sensing in the monitoring and analysis of geological disasters has many advantages, such as wide range, strong timeliness and high accuracy. The application of 3S technologies in the monitoring field of secondary geological disaster, such as landslides, collapse and debris flow is becoming more and more widely, and become a kind of effective means of monitoring.This paper chose the earthquake sensitive area of geological disasters in Yingxiu town- Yinxing Township as research area, used 3S technologies to monitor and analysis landslide and collapse geological hazards in this study. Paper used the multi-source and multi-temporal remote sensing image data(including the aerial image of the spatial resolution of 0.5 meters, the domestic high satellite images of the resolution of 2 meters and the OLI images of the resolution of 15 meters) and 1:50000 topographic map as the data source, and used digital photogrammetry technology and GIS technology to establish the virtual 3D scene of different scales in the study area. According to remote sensing image interpretation signs and topography, geological environment conditions and the surrounding objects in the study area, makes remote sensing interpretation about the study area, Landslide and information extraction. Based on the effective treatment of L-band high-resolution PALSAR radar data, obtain surface deformation information of the earthquake in the research area to support identification of geological disasters around the study area. Finally, combined with the development mechanism of geological disasters and statistical analysis on the disaster factors, evaluate the susceptibility of collapse, landslide in the study area on information quantity method, analytic hierarchy process(AHP) and weighted information quantity. The research contents and the main research results have the following several aspects:(1) When using multi-source remote sensing image to extract information first response to the image preprocessing. The pretreatment results affect the accuracy of geographic location in late remote sensing image. A 3D visualization model of the research area is established. The 3D visualization model can be truly, objectively and multi-angle to analysis the landscape, show a ground model, and improve the remote sensing interpretation accuracy and speed of geological disasters in the study area.(2) Based on the effective treatment of L-band high-resolution PALSAR radar data, make difference between the interference lines diagram by the SAR image generated(two images acquired before and after surface deformation) and by using DEM to simulate the surface information in Wenchuan area. The main steps include image registration, interferogram generation, flat-earth phase remove, the interferogram filtering, phase unwrapping, differential treatment and geocoding.(3) In order to make the remote sensing interpretation and information extraction of collapse, landslide, there are a comprehensive analysis on the features of collapse and landslide in the image, the interpretation signs of collapse and landslide, and the information extraction about the geological disaster by using the high precision aerial remote sensing images and 3D visualization dynamic analysis, and the information of surface deformation based on PALSAR data, and field investigation data in this paper. Eventually the statistics in 2008 after the earthquake in the study area geological disaster are more than 60; the affected area is 7.56495 square kilometers. There are 34 landslide geological disasters area in the study area, and the affected area is 1.06352 square kilometers in 2013. The change of the geological disasters of the collapse and the spatial distribution of the geological disasters in 2008 and 2013 were compared and analyzed.(4) On the analysis of forming conditions and forming rule of collapse and landslide, combined with previous research results, selecting slope gradient, slope, litho logy, ground elevation, vegetation cover, distance from the water system 6 factors make analysis on debris flow in the study area development characteristic. Through the information method, analytic hierarchy process(AHP) and the weighted information get susceptibility evaluation of landslide in the study area. |
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