GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.1 GNGTS 2024 Fig. 1: a) Schematic diagram of the adopted procedure for evaluating local SPTHA . b) Spatial representation of Test and Application case sites. c) Hazard maps obtained at the Application site of Ravenna for two different Average Return Periods (ARPs). Source Preselection The presence of a Probabilistic Tsunami Hazard Assessment (PTHA) model holds significant importance as it enables the preselection of specific source areas of interest within the region. This capability results in essential time savings during calculations. At local coastal sites, the offshore PTHA is not able to reproduce the tsunami, as only high-resolution onshore tsunami simulations can guarantee an acceptable level of detail for the description of the local hazard. However, regional PTHA makes a huge effort for homogeneously including all the potential sources of tsunami and for exploring existing aleatory and epistemic uncertainty (Basili et al., 2013, Selva et al., 2016; Davies et al., 2022). This effort allows quantitatively filtering out source areas that do not matter locally, without imposing any subjective qualitative choice.  Source disaggregation offers a quantitative assessment of the potential impact of a particular source area on the local tsunami hazard (Bazzurro and Cornell, 1999; Selva et al., 2016). Specifically, for a designated tsunami intensity threshold, hazard disaggregation provides a measure of the probability that a given source area can produce such an intensity of tsunami. For a specified target, the regional hazard leads to a nearby point in the regional hazard, with the most representative point for the local target (e.g., the closest point) considered. Disaggregation enables the identification of earthquake scenarios that significantly contribute to the tsunami hazard for the preselected Point of Interest (POI).