GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 11 detailed relocation of the environmental effects (Fig. 2b) shows that most of them mainly occurred in the sector embracing the eastern Hyblean area and the Catania plain, suggesting that the sources of the 1693 earthquakes are located in this area. We used the new macroseismic intensity data to assess location, physical dimensions, and orientation of the seismic sources of foreshock- mainshock pair (Fig. 3), by using the Gasperini et al. (1999) method. With respect to the CPTI15 catalogue we obtained slight small values of the equivalent magnitude, Mw = 6.1 for the foreshock and Mw = 7.1 for the main shock, respectively. The main difference with respect to previous studies regards the modelling of the seismogenic sources, considered separately for the two main shocks. Both sources are oriented NNE-SSW, suggesting that a fault with this orientation ruptured, enucleating south near Sortino at first and then northwards in the Catania Plain or offshore. Epicentres of historical earthquakes, maximum damage of the foreshock-mainshock pair, aftershocks of the 1693 sequence, maximum frequency of environmental effects and source models from macroseismic intensity data are all aligned along a NNE-SSW direction, suggesting that the seismogenic source should have been a fault with this orientation located in the eastern Fig. 2 - A) Location of some shocks of the 1693 seismic sequence (red stars) and epicenters of the earthquakes with Mw > 5.1 from CPT15 catalogue (Rovida et al., 2016). B) Detailed relocation of the 1693 environmental effects. Fig. 3 - Main faults in southestern Sicily; inferred epicentres of 1693 seismic sequence; the rectangles represent the surfaces projection of the faults obtained by using the Gasperini et al. (1999) method for the foreshock-mainshock pair.