GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.2 GNGTS 2024 anCcline area (Casaglia) to its minimum depth, at about 100 m, and largely sinks towards the subsiding southern syncline zone, where normally exceeds 300 m in depth. The deepening of the seismic substratum ships the amplificaCon peaks toward lower frequencies. To evaluate the forecasted acceleraCon at the surface, seismic microzonaCon studies require to input the seismic intensity, esCmated on the bedrock top, with a 10% occurrence probability, over a 50- year Cme interval, which is provided by the Italian seismic hazard map (Melem et al. 2006; Stucchi et al, 2011). To evaluate the seismic moCon amplificaCon induced by the unlithified straCgraphic units overlaying the bedrocks, the amplificaCon factor abacuses proposed by the Emilia-Romagna Region for alluvial plain areas were iniCally used. Two separate abacuses were applied. The “Pianura 2” abacus was used for the areas where the bedrock top is less than 150 m deep, while for the greater porCon of the municipal area, with bedrock exceeding 300 m in depth, the “Pianura 3” one was applied. The amplificaCon factors predicted by the abacuses were compared with those derived from our detailed local seismic response analyses (Fig. 2). The good match of the results supports the use of the abacuses approximaCon. The response analyses was performed in the anCcline area and in different porCons of the historic center, developed on fluvial sands or on interfluvial muds (Fig. 1, 2). We then forecasted the areal distribuCon of damage, according to the “syntheCc damage constrained parameter” (HSM, Naso 2019), related to the forecasted site shaking, expressed in cm/s 2 . The HSM values in turn support the damage esCmaCon. Medium to severe damage is expected for the largest porCon of the Municipality of Ferrara, including the whole urban area.