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During September and October 1997, an earthquake sequence of moderate magnitude struck the Umbria and Marche regions, central Italy. As a consequence of the most severe shocks, several landslides were triggered on bedrock, calcareous debris and sandy clay deposits. The landslide inventory, collected in the field and by aerial-photo interpretation, provided an opportunity to test the accuracy of existing predictive relations for landslide hazard zoning and to formulate new ones. Shallow soil slides and debris slides were selected to verify the prediction performance of the methods, which are based on a simplified model [Geotechnique 15 (1965) 139] that calculate landslide displacements during Cyclic seismic loading. Rock falls were modeled using a different approach to produce an empirical predictive rule for determining the probability of detachment of blocks. When landslides occur along pre-existing or newly formed failure surfaces, the Arias intensity and destructiveness potential are the strong ground-motion parameters that best relate to displacements. The predictive relation proposed for rock falls evaluates the probability of occurrence as a function of the slope angle and the peak ground acceleration (PGA). (C) 2003 Elsevier Science B.V. All rights reserved.

During September and October 1997 a seismic sequence of moderate magnitude struck the Umbria and Marche regions, central Italy. As a consequence of the main shocks several rock falls were triggered along the flanks of the Valnerina valley, an important canyon formed by the erosion of the Nera river on limestone formations. This landslide data set was used to explore the correlation existing among rock falls and several causal factors, like slope angle, geology and strong ground motion parameters. All the data have been digitised and georeferenced with the aid of a Geographic Information System in the form of digital thematic layers. The landslide inventory has been overlaid to the maps of causal factors, and the result arranged in order to create a data structure suitable to perform a multivariate statistics. A multiple regression allowed to formulate a predictive rule that can be used to produce a rock fall susceptibility map in case of an earthquake, in regions with similar geologic and geomorphologic characteristics. (C) 2002 Elsevier Science Ltd. All rights reserved.