GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.1 273 In order to obtain a realistic flooding scenario in the study area, we estimated the maximum tsunami flooding from eq. (2), using run-up and period from historical accounts and comparing the results with the inundation values coming from historical and geological data. Sites have been classified on the basis of their coastal type: very flat topography (Marzamemi port, Marinelli and Morghella beaches); flat topography (Lido di Noto, Eloro, Calamosche, Vendicari, San Lorenzo and Marzamemi beaches); gently sloping rocky platform (Vendicari and San Lorenzo); sloping rocky platform (Calabernardo, Lido di Noto, Eloro, Calamosche, Punta Bove Marino, Marzamemi, Morghella and Torre Fano); Cliff at Vendicari 4 m high; cliff > 6m. For the 1693 historical tsunami, we adopted the minimum run-up R min = 1.2 m and a medium run-up R med = 2.5 m observed at Siracusa, and for the 1908 tsunami the value of 1.5 m observed at Capo Passero (Gerardi et al. , 2008). Furthermore, for the 1908 tsunami we used a medium wave period T = 8 min reported by historical reports (Baratta, 1910), whereas for the 1693 tsunami a medium period of T = 7 min obtained by modelling the tsunami source by Tinti et al. (2001). Finally, for the 365 tsunami we used run-up values and a period obtained by Lorito et al. (2008) modelling the tsunami source. Historical reports describe that at Calabernardo, during the 1908 tsunami, the flooding waves reached the topographic height of 10 m (Baratta, 1910). Therefore, we computed tsunami flooding considering also a run-up of 4.5 m, to give a possible explanation of the observed accounts. Table 2 - Maximum inundation obtained applying equation (2). Historical run-up R in the nearest localities. Date R min (m) R med (m) R (m) T (s) α X max Very flat topography 365 AD 2 1400 2.1 1235.6 1693 1.2 400 2.1 273.5 1693 2.5 400 2.1 394.7 1908 1.5 480 2.1 366.9 flat topography 365 AD 2 1400 5.4 1234.1 1693 1.2 400 5.4 273.1 1693 2.5 400 5.4 394.2 1908 1.5 480 5.4 366.4 gently sloping rocky platform 365 AD 2 1400 4.6 1235.6 1693 1.2 400 4.6 273.5 1693 2.5 400 4.6 394.7 1908 1.5 480 4.6 366.9 sloping rocky platform 365 AD 2 1400 11.6 1214.3 1693 1.2 400 11.6 268.7 1693 2.5 400 11.6 387.9 1908 1.5 480 11.6 360,6 4 m high cliff 365 AD 4.5 1400 8.5 613.0 1693 4.5 400 8.5 175.1 1908 4.5 480 8.5 210.2