Tsunami Induced by Landslides on the Island of Ischia: numerical simulations and hazard analysis

This study investigates tsunami generation induced by landslides on the island of Ischia, located in the Tyrrhenian Sea, an area particularly vulnerable due to its unstable slopes and proximity to densely populated coastlines. The research utilizes a dataset of 165 documented landslide events, which were analysed to reconstruct "ideal" landslides based on parameters such as area, volume (ranging from 10³ m³ to over 10⁷ m³), average length and width, centroid coordinates, and deposit thickness. These parameters were used to create representative geometric models for numerical simulations with the COMCOT model. The COMCOT model, known for its ability to simulate tsunami generation, propagation, and coastal interaction, was applied to landslides of varying sizes and orientations. Eleven observation points along the island's coast were defined to track changes in wave height, energy distribution, and the temporal evolution of impacts. Results show that large-volume landslides generate significantly higher and more destructive waves, with local amplifications occurring in areas of irregular bathymetry, such as coves and bays. Simulations revealed that landslides oriented to the north produced waves reflected towards the open sea, reducing direct impact on the coast. In contrast, landslides oriented to the east generated higher waves with direct propagation towards the Gulf of Naples, increasing the risk of flooding in ports and urban areas. The largest waves, exceeding 10 meters in height, were observed in scenarios involving large-volume landslides, underscoring the destructive potential of such events. This study introduces a novel methodological approach by modeling landslides based on real data from a large database of different landslides in the area.