GNGTS 2013 - Atti del 32° Convegno Nazionale

couple, the condition Ai > Ai +1 is tested and if it is verified, an estimate of pseudo-frequency v and damping ζ is calculated. From these estimates, a histogram is then built considering pairs of pseudo-frequency and damping values. The fundamental period and damping experimentally obtained through noise measurements were also compared with the ones obtained by empirical formulas. These period-height relationships (i.e. Eurocode8, 2003; EC8 – RC; EC8 – MA) calculate the fundamental period (T) as a function of the buildings geometry, usually the height (H) or the number of floors (N). In order to predict the expected ground motion parameters in terms of peak ground acceleration (PGA) peak ground velocity (PGV), and Spectral Acceleration (SA) as a function of distance and magnitude we used the latest version of EXSIM program (Boore, 2010). It is a modified version of the FINSIM (finite fault simulation) code developed by Beresnev and Atkinson (1998). The simulations were carried out by using the regional propagation parameters for southeast Sicily (Scognamiglio et al. , 2005) and rectangular faults having length and width proportional to the moment magnitude according the relationship proposed by Wells and Coppersmith (1994). Moreover, considering the potential seismic effect due to the local geology (Nunziata et al. , 2000; Panzera & Lombardo, 2013), we produced a reliable earthquake scenarios by simulating the M w =5.8 earthquake that occurred on 13 th December 1990 off-shore of eastern Sicily between the cities of Catania and Siracusa on the Malta escarpment fault system (Fig. 3). Finally, take into account different site conditions, we refer to the V S,30 classification. Description of results and concluding remarks. Site effects at a specific location are very important and can be used for engineering purposes to define the regional predictive law and the seismic hazard. A generalized site response concept is indeed useful to create a detailed shaking map for a region where the different outcropping lithologies are known. The evaluation of the dynamical properties of buildings and of the ground motion scenario in the Siracusa area gave significant suggestions about potential critical conditions due to soil-structure interaction. The results obtained can be summarized as follow. • Spectral ratios of the ambient noise measurements provided reliable estimates of the fundamental period of analyzed buildings. The measured periods were used to obtain period-height relationships which set into evidence that the experimental values are lower than those postulated by Eurocode8 (2003). Such finding could be explained Fig. 3 - Contour of PGA and PGV obtained for the 1990 earthquake scenario. 107 GNGTS 2013 S essione 2.1