Probabilistic assessment of earthquake-induced landslide hazard including the effects of ground motion directionality

Earthquake ground motions can vary in different horizontal directions. These directional variations need to be included in the earthquake-induced landslide hazard assessment. This paper examines the influence of ground motion directionality on the probabilistic seismic displacement hazard of slopes. The distribution of the orientation of the maximum sliding displacement direction are analyzed, and the optimal ground motion parameters are provided by which the displacement in the orientation of maximum ground motion parameters can be used to represent the maximum sliding displacement over all orientations. Predictive relationships of orientation-independent sliding displacements are developed for different types of ground motions (i.e., forward-directivity pulse and non-pulse ground motions). The proposed relationships for sliding displacement are based on ground motion parameters for which there are available ground motion prediction equations (GMPEs), hence allowing for fully compatible hazard analyses with existing GMPEs. Probabilistic assessment of earthquake-induced landslide hazard is performed for hypothetical slopes, and the seismic landslide hazard maps and the ground-motion selection procedure for site-specific analysis of slopes are presented by including the effects of ground motion directionality in different types of ground motions.