Mapping earthquake-induced landslide susceptibility in central Italy

In this work, a model to forecast the spatial distribution of earthquake-induced landslide hazard at the regional scale has been developed. The model adopts a displacement–based approach, solving the Newmark equation for the infinite slope problem for each cell of a regular grid discretizing the study area. In Newmark’s approach, seismic slope stability is measured in terms of the ratio of accumulated permanent displacement during the earthquake and the maximum allowable one, depending—in principle—on the definition of tolerable damage level. The computed permanent displacement depends critically on the actual slope stability conditions, quantified by the critical acceleration, i.e. the seismic acceleration bringing the slope to a state of (instantaneous) limit equilibrium. Given the slope features (physical and mechanical properties, geometrical and topographical settings and pore pressure regime) for each cell and the earthquake characteristics, the model is able to predict the potentially unstable zones over the study area. The 1997 Umbria-Marche earthquake has been selected as a benchmark for the model. The model predictions have been compared with an available database of actually occurred landslides after the considered earthquake, and a good correspondence between the predictions and actual field observations has been obtained.