Demand Hazard Curves for the Assessment of Seismic Induced Slope Displacements in Ischia Island

This study is part of wider research aimed at the evaluation of ground instability and permanent deformation related to landslides and liquefaction in the volcanic island of Ischia adopting a multi-hazard approach. Ischia was frequently interested by instability caused by both hydro-meteoric and seismic events, the latest of which occurred with an unusual spatial and temporal concentration in 2009, 2017 and 2022 in the same area of Casamicciola. The research is aimed at tentatively evaluate potential cascading effects related to ground instabilities considering the variable susceptibility to seismic instability related to the groundwater fluctuation induced by meteoric events. Here the results of a probabilistic assessment of seismic induced slope displacements carried out with reference to the north-western part of Ischia Island, recently hit by the earthquake, are presented. The study allowed the construction of specific demand hazard curves expressed in terms of annual rate of exceedance of permanent earthquake induced slope displacement. These curves can be a useful tool to be used by both planners and designers. The resulting hazard maps, based on a probabilistic approach, represent the first step toward a multi hazard analysis.