GNGTS 2013 - Atti del 32° Convegno Nazionale

Site classification maps for two test areas based on geological map at 1:50,000 scale. The next step has been the analysis of actual usability of the data contained in the evaluations of site specific hazard presented in the previ- ous pages, crossed with more detailed geological data. In particular, we start- ed from the map of and analyzed two geological sheets from CARG project, both of them at 1:50,000 scale: “Mode- na” (ISPRA 2009) and “Udine” (APAT 2008). In Figs. 3a and 3d the a g values are amplified considering stratigraphic NTC 2008 AFs for, respectively, the Modena and Udine areas with the site classifica- tion based on geological data from the INGV-ISPRA (1:100.000; Di Capua et al. , 2011) national dataset . For the same areas, the a g are ampli- fied considering stratigraphic NTC 2008 AFs on the basis of the CARG cartogra- phy “Modena” and “Udine” (1:50,000, Fig. 3b and Fig. 3e, respectively). In the case of Modena test area the PGA var- iation using a more detailed geological information is visible but not so strong In the case of Udine test site the differ- ences in site-specific PGAs are higher and noticeable. The CARG sheet Udine changes radically the geological interpretation with respect to the INGV-ISPRA 1:100,000 data geological map, consequently a large part of site-specific PGA values changes radically, not only for the best map resolution. Comments. The maps here presented and developed in the frame of the S2 project showed two main results: • A map of site-specific hazard for a wide portion of Northern Italy, obtained from the site classification of the examined data extracted from geological/lithological maps at 1:100,000 scale. • Two maps of site-specific hazard, respectively for the test areas of Modena and Udine, obtained by a site classification based on geological/lithological data at 1:50,000 scale, derived from maps produced by the CARG Project (APAT, 2008; ISPRA, 2009). Fig. 2 – a) soil seismic hazard map of the study area representing the PGA with a 475-year return period computed by considering lithological NTC 2008 AFs; b) differences between site-specific PGA from NTC 2008 AFs ( and PGA site-specifc from OPCM 3274/2003 AFs. c) differences be- tween site-specific PGA from NTC 2008 AFs and PGA site-specifc from EC08 (2003) AFs. Red/ orange values indicate higher values of the NTC 2008 AFs map. 121 GNGTS 2013 S essione 2.1