Identification and analysis of secondary geological hazards triggered by a magnitude 8.0 Wenchuan Earthquake

Large quantities of secondary geological hazards such as rock falls, landslide as well as debris flows were triggered by a magnitude 8.0 earthquake of Wenchuan, Sichuan, China. The identification of about 46560 secondary geological hazards through visual interpretation of multi-source remote sensing data over 14 counties in heavy disaster region after the overall remote sensing data were obtained. Their location and area information was input into GIS database. The distribution map, dot destiny map, histogram of number, total area, average area, area ratio, frequency of secondary geological hazards in 14 counties were drawn. Four regions of intensive geological hazards were identified. It is shown that there is a corresponding relation between the distribution of secondary geological hazards and the main faults. At last, the relation between the distribution and elevation, slope angle and intensity of earthquake triggered geological hazards were established. About 54.00 percent of secondary geological hazards in the study area occurred between altitude of 1000m and 2000m; about 62.42 percents of secondary geo- logical hazards occurred between slope angle of 30° and 50°; about 90.94 percents of secondary geological hazards occurred between Ⅺ and Ⅷ intensity. This paper provides an important database of secondary geological hazards triggered by Wenchuan Earthquake for further research on development trend, mechanism, prediction of secondary geological hazards, restoration and rebuilding, site selection, etc.