Abstract. According to a deep-rooted conviction, the occurrence of a tsunami in the Mediterranean Sea would be very rare. However, in addition to the catastrophic event of Messina and Reggio Calabria (1908) and the saved danger for the tsunami occurred on Cycladic sea in 1956, 44 events are reported in the Mediterranean Sea between 1951 and 2003, and other smaller tsunamis occurred off Morocco, Aegean and Ionian seashores between 2017 and 2018. Such events, that are just a little part of the over 200 historically events reported for the Mediterranean (Maramai, Brizuela & Graziani, 2014) should remind geoscientists, civil protection officers, media and citizens that 1) tsunami hazard in the Mediterranean is not negligible, and 2) tsunamis come in all shapes and colours, and even a small event can result in serious damages and loss of lives and properties. Recently, a project funded by the European Commission (TSUMAPS-NEAM, Basili et al., 2018) has estimated the tsunami hazard due to seismic sources in the NEAM region (one of the four ICG coordinated by the UNESCO IOC) finding that a significant hazard is present in most coasts of the area, particularly in those of Greece and Italy. In such a scenario, where low probability and high uncertainty match with poor knowledge and familiarity with tsunami hazard, risk mitigation strategies and risk communicators should avoid undue assumptions about public’s supposed attitudes and preparedness, as these may results in serious consequences for the exposed population, geoscientists, and civil protection officers. Hence, scientists must carefully shape their messages and rely on well-researched principled practices rather than on good intuitions (Bostrom, & Löfstedt, 2003). For these reasons, the Centro Allerta Tsunami of the Istituto Nazionale di Geofisica e Vulcanologia (hereinafter CAT-INGV) promoted a survey to investigate tsunami’s risk perception in two pilot regions of Southern Italy, Calabria and Apulia, providing a stratified sample of 1021 interviewees representing about 3.2mln people living in 183 coastal municipalities of two regions subjected (along with Sicily) to relatively high probability to be hit by a tsunami. Results show that people’s perception and understanding of tsunami are affected by media accounts of large tsunamis of 2004 (Sumatra) and 2011 (Tohoku, North East Japan): television emerged as the most relevant source of knowledge for almost 90 % of the sample, and the influence of media also results in the way tsunami risk is characterized. Risk perception appears to be low: for almost half of the sample the occurrence of a tsunami in the Mediterranean sea is considered quite unlikely. Furthermore, the survey’s results show that the word tsunami occupies a different semantic space with respect to the Italian traditional headword maremoto, with differences among sample strata. In other words, the same physical phenomenon would be understood in two different ways by younger, educated people and elders with low education level. Also belonging to different coastal areas appears to have a significant influence on the way tsunami hazard is conceived, having a stronger effect on risk characterization, for instance the interviewees of Tyrrhenian Calabria are more likely to associate tsunami risk to volcanoes with respect to other considered coastlines. The results of this study provide a relevant account of the issues at a stake, also entailing important implication both for risk communication and mitigation policies.
Probabilistic tsunami inundation assessment of Kuroshio Town,Kochi Prefecture, Japan considering the Nankai-Tonankai megathrust rupture scenarios
