GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 9 Pettenati, 2001; Barbano and Rigano, 2001). Furthermore, given the absence of clear evidence of surface faulting and relevant faults in the area of maximum effects, various Authors proposed several faults located nearby as sources of these earthquakes (DISS Working Group, 2018 and references therein). In order to contribute to the debate, we performed a revision of the macroseismic data of the 1693 shocks by using data retrieved from the CFTI5Med catalogue (Guidoboni et al. , 2018) and recomputed the seismic sources by using the boxer method (Gasperini et al. , 1999). In summary, we reanalysed historical reports and reassessed intensities by using the European Macroseismic Scale (Grüntal, 1998), localized some of the more than 1800 aftershocks that contribute to the destruction of eastern Sicily, and mapped in detail environmental effects, after their careful classification. The January 9 foreshock is usually described in the historical sources along with the main shock of January 11. Only few accounts report detailed effects for some localities. Given the heavy damage and fatalities that were caused in some of them (Table 1), it is likely that in near localities there were damage as well. Therefore, the macroseismic field is likely incomplete (Fig. 1a). The shock mainly damaged the eastern side of Hyblean Plateau and was felt in Palermo, Messina and in the Malta Islands. Tab. 1 - Localities for which historical sources report victims caused by the 9 January foreshock. Locality IEMS Fatalities Historical Sources Augusta 8-9 200 AGS, 1693 Avola Vecchia 8-9 500 Dell’Arte, 1699 Noto Antica 8-9 200 Tortora, 1712 Giarratana Vecchia 8 many Dell’Agli, 1886 Siracusa 7-8 3 + 100* Memoriale, ms 1698 Palazzolo Acreide 7-8 mortality of people ACMPA, 1693 Catania 8 10 Amico, XVII cent. Lentini 8-9 4 Burgos, 1693 Melilli 8-9 Some ACMM, 1693 Brucoli 7-8 4 AGS,1693 Vizzini 8 mortality of people Boccone, 1687 total More than 1021 * in the countryside The January 11 earthquake was undoubtedly the largest shock of the 1693 sequence, which continued for more than two years (e.g. Boccone, 1697). It nearly destroyed about forty towns in the area between Catania, Siracusa and Ragusa, most of them already damaged by the January 9 shock, and more or less damaged most of the Sicilian towns and villages as far as Messina, Palermo, and the Maltese Islands. It was felt in northern Calabria, along the Africa coast and probably also in Greece. The wide extension of the damaged area, the great amount of victims (more than 60000 in total), the numerous environmental effects in southeastern Sicily, make it one of the most destructive events in the Italian seismic history. The January 11 shock generated a strong tsunami that hit the Ionian coasts of Sicily, from the Messina Straits to the southern coast and, according to some coeval sources as far as the Malta Islands (De Soldanis, 1746). The newmacroseismic field (Fig. 1b) shows few differences with respect to the one available in CFTI5Med (Guidoboni et al. , 2018). The key changes concern the intensity assessment in some localities. Indeed, we selected to assess the same intensity to all the localities with the