Tsunamis, although of rare occurrence compared to other natural disasters, can have devastating consequences for society's increasingly populated coastal areas. Subaerial or submarine landslides are the second most frequent tsunami source. Performing a comprehensive tsunami hazard assessment for a given area is certainly one important tool in order prevent possible disaster. However, hazard analysis for landslide induced tsunami is in general difficult in view of the large uncertainties associated with the complex and diverse nature of the tsunamigenic source parameters, combined with their infrequent event records making prognostic modelling challenging.
We present an efficient model to perform such hazard analyses, based on solving the linear mild-slope equation with a time-dependent source term representing the seafloor motion. The proposed approach allows carrying out many computations, for a large number of landslide scenarios at a reduced computational cost compared to other available methods, while still providing physically accurate simulations of most landslide tsunami generation and propagation.
Tsunamis are long gravity water waves generated by a sudden vertical perturbation of the seafloor or the sea surface, resulting from impulsive geological events, such as earthquakes, landslides, or volcanic eruptions.
Tsunamis generated by landslides represent one of the greatest hazards for coastal populations and infrastructures, because they often occur in proximity to the shore, their amplitude is related to the potentially large vertical motion of the landslide, and they offer little time for warning.
Submarine landslide tsunami sources are widespread and may dominate tsunami hazard, for instance, on the break and slope of the wide continental shelf bordering the US East coast (Ten Brink et al., 2014; Schambach et al., 2019), which is the site of the 1929 Grand Banks tsunami that caused 27 fatalities in Newfoundland (Løvholt et al., 2019); and on the slope of the narrow shelf off of the French-Italian riviera (e.g., Ioualalen et al., 2010). A tsunami caused by a submarine landslide (a slump) was shown to have been the major source of the devastating Papua New Guinea 1998 tsunami, that caused over 2000 fatalities (Tappin et al., 2008), and a rigid slump on the submerged slopes of Mount Etna is believed to have been the major tsunamigenic source for the 1908 Messina earthquake, the worst natural disaster in modern history in the Mediterranean basin, responsible for 80000 fatalities (Schambach et al., 2020). More recently, many coastal submarine landslides triggered by the earthquake contributed to the over 2000 fatalities caused by the Palu 2018 tsunami (Schambach et al., 2021).
