Landslides, as one of the major natural hazards, account each
year for enormous property damage in terms of both direct and
indirect costs. Landslides, defined as the movement of a mass
rock, debris or earth down a slope (Cruden, 1991), can be
triggered by a variety of external stimulus, such as intense
rainfall, earthquake shaking, water level change, storm waves or
rapid stream erosion that cause a rapid increase in shear stress
or decrease in shear strength of slope-forming materials. In
addition, as development expands into unstable hillslope areas
under the pressures of increasing population and urbanization,
human activities such as deforestation or excavation of slopes
for road cuts and building sites, etc., have become important
triggers for landslide occurrence (Dai et al., 2002).