An assessment method for regional susceptibility of landslides under coupling condition of earthquake and rainfall

Based on the Mohr-Coulomb failure criterion, a formula to calculate the factor of safety for landslide under coupling condition of earthquake and rainfall is deduced by introducing the inertia force of ground motion and groundwater factor. Then, by applying frequency analysis of physical and geometric parameters of slip mass and Monte Carlo simulation, a method to estimate sliding probability of landslides under coupling condition is developed. Consequently, the theoretical matrix, which considers influences of ground motion, slope angle, soil type and groundwater factor on sliding probability of landslides synthetically, is established to assess the risk probability of landslides under coupling condition. The earthquake, in fact, is a small probability event. For thinking over the occurrence probability of actual earthquake in any certain research region, it is better to calculate the repeated probabilities of ground motion according to its background seismicity. By the reoccurrence probabilities of ground motion, the above-mentioned theoretical matrix could figure the actual risk probability of landslides associated with earthquake events in any interesting region. According to the two kinds of theoretical matrixes, the probabilistic assessment for regional susceptibility of landslides under coupling condition should be achieved by GIS, data of digital geological map and high-precision DEM in a certain research region. As the case of Kitakyushu City, Japan, the procedure is applied to investigate the regional susceptibility of landslides under coupling condition in this city and the probabilistic assessment results are provided in the end.