Modelling of tsunamigenic scenarios using NamiDance for selected areas along the coast of Northern Adriatic Sea

Abstract

Significant tsunamis in Northern Adriatic are extremely rare and only a few historical events were reported in the literature, with possible sources mostly located along with central and southern parts of the Adriatic coasts. Recently, an alert tsunami system has been established for the whole Mediterranean area, including the Adriatic Sea. However, a detailed description of the potential impact of such waves on coastal areas, particularly urban ones, is still missing. The scope of this thesis is to model the hazard associated with possible tsunamis, generated by relatively distant earthquakes (i.e., with epicentres located at few hundred kilometres distance, and arrival times of hours), for urban areas located along the Northern Adriatic coasts. Tsunami modelling is performed by the NamiDance software, which allows accounting for seismic source properties, variable bathymetry, and nonlinear effects in waves propagation. Urban scale hazard scenarios for selected cities are developed considering different potential tsunamigenic sources of tectonic origin, located in the Central and Southern Adriatic Sea. Sources are defined according to available literature, which includes catalogues of a historical tsunami and existing largescale models. Information about the morphology of the study areas (i.e., bathymetry, topography) available at OGS is used, along with additional data retrieved online and from literature. A set of tsunami scenarios is modelled, considering possible sources related to historical events, as well as extremely large events not yet observed; parametric tests are performed, for increasing scenario earthquakes magnitudes (i.e. source size), to account for seismic source variability. Preliminary tsunami hazard estimates, which may allow developing inundation scenarios, are computed for selected cities, namely Trieste, Monfalcone, Lignano and Grado, depending on data availability and on the relevance of the site. Accordingly, a preliminary set of tsunami-related parameters and maps are obtained, including maximum runup at the selected sites; arrival time of the first wave along the coast; time series of water level fluctuations at selected locations (mareograms); tsunami propagation maps; distributions of the arrival time of the maximum swell along the coast.