Analysis of seismic hazard in landslide-prone regions: criteria and example for an area of Daunia (southern Italy)

In relation to the assessment of earthquake-induced landslide hazard, this paper discusses general principles and describes implementation criteria for seismic hazard estimates in landslide-prone regions. These criteria were worked out during the preparation of a hazard map belonging to the official Italian geological cartography and they are proposed as guidelines for future compilation of similar maps. In the presented case study, we used a procedure for the assessment of seismic hazard impact on slope stability adopting Arias intensity Ia as seismic shaking parameter and critical acceleration ac as parameter representing slope strength to failures induced by seismic shaking. According to this procedure, after a preliminary comparison of estimated historical maximum values of Ia with values proposed in literature as landslide-triggering thresholds, a probabilistic approach, based on the Newmark’s model, is adopted: it allows to estimate the minimum critical acceleration ac required for a slope to keep under a prefixed value, the probability of failures induced by seismic shakings expected in a given time interval. In this way, one can prepare seismic hazard maps where seismic shaking is expressed in an indirect way through a parameter (the critical acceleration) representing the ‘‘strength’’ that seismic shakings mobilise in slope materials (strength demand) with a prefixed exceedance probability. This approach was applied to an area of Daunia (Apulia—southern Italy) affected by frequent landslide phenomena. The obtained results indicate that shakings with a significant slope destabilisation potential can be expected particularly in the northwestern part of the area, which is exposed to the seismic activity of Apennine tectonic structures.