GNGTS 2013 - Atti del 32° Convegno Nazionale

Fig. 1a shows the map of the lithological classification derived from the geological/ lithological map (INGV-ISPRA original data at a 1:100,000 scale, Di Capua et al. 2011). If we apply a discretization of map of with a 0.05° grid the outcome is clearly unsatisfactory because the geological map is more detailed (Fig. 1b). For this reason we decided to apply the discretization with 0.02 grid following the site classification (NTC 2008; Fig. 1c). The geological discretization of Fig. 1c is used to amplify the ag and F0 parameters (475 year return period), for the same 0.02° grid and we obtained the map in Fig. 2a. The next step was to compare our results with those obtained applying other Code litho-stratigraphic AFs to the same grid. Fig. 2b and Fig. 2c show respectively the differ- ences between site-specific PGA from NTC 2008 AFs (and PGA site-specifc fromOPCM 3274/2003 AFs OPCM 3274/2003 AFs (Fig 2b) and the EC8 (2003) AFs (Fig. 2c). The two maps in Figs. 2b and 2c are very similar and both indicate clearly higher values (red and orange) in the Plain area of Emilia Romagna for the NTC 2008 AFs map (Fig. 2a). Comparing the two maps it is also visible a tendency of higher values (orange) in the map of Fig. 2c along the piedmont strip in Veneto and Friuli indicating higher values of the NTC 2008 AFs map compared to EC08 (2003) AFs map. Fig. 1 – a) geological/lithological map original data (1:100.000, source INGV-ISPRA - Di Capua et al. , 2011); b) grid 0.05° step overlaying the geological map of Fig. 1a; c) discretized geological/lithological map on the 0.02° grid. Tab. 3 – Table of classification of soils and litho-stratigraphic AFs. NEHRP Class NEHRP V30 (m/s) NEHRP AFs Italian and EC8 Class Italian and EC8 V30 (m/s) EC8 AFs OPCM3274/03 AFs NTC08 AFs A - Hard rock >1500 0.8 1 B - Rock 760-1500 1.0 A - Rock >800 1 1 1≤Ss≤1.2 C - Very dense soil and soft rock 360-760 1.2 B - Stiff 800-360 1.2 1.25 1≤Ss≤1.5 D - Stiff soil 180-360 1.5 C - Soft 360-180 1.15 1.25 0.9≤Ss≤1.8 E - Soft soil <180 2.1 Very soft <180 1.35 1.35 1≤ Ss≤1.6 120 GNGTS 2013 S essione 2.1