GNGTS 2018 - 37° Convegno Nazionale

10 GNGTS 2018 S essione 1.1 Fig. 1 - Left: the January 9 foreshock. In the reported localities there were fatalities (see table 1). Right: the January 11 January foreshock. Intensity estimated by using EMS-98 scale. similar description. Furthermore, since building number and vulnerability are unknown and we cannot estimate the correct value according to the EMS-98, we assigned 10-11 instead of 11 MCS in towns with total destruction, and 10 when the accounts report that some buildings did not collapse. This uncertain assessment takes also into account the cumulated effects of the previous strong shock. Through the revision of the macroseismic data of the 1693 main shocks, we obtained that the 9 January earthquake source is located near Sortino (Fig. 1a), adjacent to the epicenter reported by the CPTI5 catalogue (Rovida et al. , 2016). On the other hand, the source of the 11 January earthquake seems to be located northward, compared to literature data. Indeed, the assessment of I = 10-11 rather than I = 11 implies a significant change in the earthquake location. Using CFTI5Med data the epicenter is constrained by only the five points of I = 11, and it is located near the 9 January shock, whereas using our data location is evaluated by using all points of I = X and I = X-XI and is located in the coastal area south of Catania (Fig. 1b). The location of the 11 January shock northernmost with respect to the 9 January shock, as already proposed by Azzaro and Barbano (2000) and Barbano and Rigano (2001), is also supported by the destruction of the village located north of Catania that were not damaged by the 9 January shock. However, cumulative damage effects bias the macroseismic field of the main event. Therefore, considering that the 11 January was followed by a strong tsunami, its source could be located off shore. The destruction followed by the 11 January shock makes difficult to estimate intensity and epicenters of the thousands of aftershocks that followed the events. Only few sources report day, time and effects of these shocks and most of them were not written in the area of destruction, where survivors were busy cleaning up debris, burying wounded and dead and getting water and food. In the CPTI5 catalogue are recorded ten events, most of them retrieved from Boschi and Guidoboni (2001). We estimated epicenters of some of the strongest shocks for which in the historical sources are reported at least four localities (Fig. 3a). The quality of location and intensities values is poor because the estimation of damage for almost completely destroyed sites is difficult. A lot of historical accounts (e.g. Boccone, 1697; Bottone, 1718; Bonaiuti, 1793) report the numerous and widespread seismogeological effects, such as landslides, damming, liquefactions, ground deformations and hydrological anomalies mainly caused by the main shocks. The