Time probabilistic evaluation of seismically induced landslide hazard in Irpinia (Southern Italy)

A recently proposed method, which incorporates the Newmark model to evaluate the earthquake-induced landslide hazard at regional scale, was applied to Irpinia, one of the most seismically active regions of Italy. The method adopts a probabilistic approach to calculate values of critical acceleration a_c representing the minimum strength required for a slope not to fail at a fixed probability level in a given time interval. Regional probabilistic hazard maps were generated for the two failure types most common in Irpinia (slump–earthflows and rock falls). The results suggest that quite moderate critical acceleration (0.05–0.08 g) could suffice to keep the slope failure probability low. However, the available data indicate that potential slide surfaces with a_c below these values could be common in Irpinia, where, perhaps in relation to particular geo-environmental conditions, a relative large number of marginally stable slopes might survive other destabilising actions and fail even on occasion of not particularly strong earthquake shaking.