Extraction Of Active Fault Based On The RS And DEM Data

The Sichuan-Yunnan region is situated in the southeastern margin of the Tibetan Plateau. Since Cenozoic time, the jointed affection of eastward motion of the Tibetan plateau and indentation of the Assam wedge cause complex tectonic deformation and intense fault activities in this region. The occurrence of a great earthquake at any time is quite possible. Detailed exploration of the region's fault, in particular, the distribution and the character of active faults have important value. The traditional methods of geological work need more time and laborious. At the same time, remote sensing images have the function of summary. Using remote sensing and GIS technology can provide guidance to extract fault structure interpreted information accurate and rapidly. The accuracy and speed of traditional interpretation of geological can be improved. The study take the area of Xichang-Miyi which located in the southwest of Sichuan province as example , and the method of using DEM data and RS to study the distribution of active faults and property is discussed.The paper summarizes the study progress of tectonic landform and the method of the extraction of fracture and the study of nature by RS and GIS. There are less research to extract the fracture by analysis topography and geomorphology with the DEM data, which is the innovative points of the study.The symbol of the fault is summarized by analyzing the characteristics of the image features composed of different colors and morphology of faults and geological, geomorphologic, water, vegetation and related surface features controlled, reformed and effected by the faults in Remote sensing images.Among lots of methods of image enhancement, ETM743 band are selected for color composite to fully display the morphological characteristics of surface features and internal structural details, and the image information of the fault is outstanding. At the same time, the image of shadow of mountain is extracted by ArcGIS with the DEM data, which highlights the linear texture of the image; Analysis of the surface slope is used to highlights the area of mutation and steep slope linearly distributed; extract water system automatically by Arc Hydro Tools. The water system fully reflect the water distribution characteristics and topographic information, in the study area, which is controlled by the tectonic movement. According to the fault interpretation signs, combine several methods, verify mutually, analyze comprehensively and extract fault. Display the three-dimensional effect by stacking the ETM image, DEM data and the extracted faults, and verify the faults by three-dimensional analysis. Help to determine the direction of fracture extension more accurately.Total 162 faults are extracted in this research. These faults contain five groups of NS trending, NW trending, NWW trending, NE trending and EW trending. According to the interpretation signs for the analysis of the character of fault, study the activity, horizontal movement features and vertical movement features of faults based on the processed data, and then summarize the features of these faults by group. Check the extracted faults combined with the 1:20 0000 geological report and geological map of this region. Most of the faults are confirmed, so it is feasible to extract fault by RS data and especially the DEM data. New faults are found and the further field verification is required. These new fractures are the supplement to the traditional field geological work. Extract fracture by RS and GIS measure have important reference to the study of the fracture of the other parts of Sichuan-Yunnan region which have similar nature environment and tectonic setting.