GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 extensive dataset, the Regione Emilia-Romagna has been subdivided into seismic macro-zones (MS Working Group, 2008; Fig. 2). Fig. 2: Seismic macro-zones (MS Working Group, 2008) according to the regional abacuses. With the aid of that map, it is possible to associate each V S measurement with the reference abacus for the estimation of local effects at the site of analysis. This procedure allows for the calculation of the value of the amplification factors for Peak Ground Acceleration (F PGA ). These factors were then multiplied by the a g values from MPS04 hazard model (475 years return period) in order to obtain the new a max . Figure 3 shows a comparison between the a max map based on the NTC18 subsoil classes (Fig. 3a) and the a max map calculated with the regional abacuses (Fig. 3b). This comparison highlights important differences. Regarding a max , for example, the regional abacuses generally provide higher values ​ except for the Reggio Emilia plain along the Po, the Comacchio Valleys, the Po delta and the coast north of Rimini, where the NTC18 amplification factors overestimate a max because they don’t consider the great seismic bedrock depth in that area. This new map allows us to better appreciate some peculiarities that are not highlighted by the previous map, such as, for example, the alignment of a max values ​ between 0.25 and 0.3 g from north of Modena to Ferrara along the buried arcs of the Ferrara Folds (Pieri and Groppi, 1981). There, composite and individual seismogenic sources are mapped in the DISS 4 database and are believed to have played a major role for the 2012 seismic events (Fig. 3c). In the Rimini area, where both onshore and offshore seismogenic sources are mapped (Adriatic Folds of Pieri and Groppi, 1981), as well as in the Romagna Apennines the new map shows a max values ​ exceeding on average 4 Available online: https://diss.ingv.it/diss330/dissmap.html