GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 In areas where V S gradually increases with depth and the seismic bedrock is at depths > 50 m (e.g., in the alluvial plains and in outcropping/sub-outcropping areas of non-rigid substrate), we used the Vs 30 value, that is the mean equivalent V S value in the first 30 m of subsoil (EN 1998-1, 2004; NTC, 2018). Vs 30 was computed by setting H=30 m in the equation above and considering the local physical properties down to that depth. If V S does not increase gradually with depth and a specific discontinuity occurs at a minimum of 3 m depth such that V S2 /V S1 ≥ 2 (where V S1 is the value of V S above and V S2 beneath the discontinuity), and if the seismic bedrock is at <50 m, then we also calculated V SH in addition to V S30 , where H is the thickness used to calculate V S1 . Not all computations yielded reliable results, and we discarded those V S representing clear outliers from the surrounding internally consistent values. V S distribution in the Regione Emilia-Romagna Fig. 1 shows the distribution of V S in Emilia-Romagna according to velocity classes reflecting level 2 MS criteria (Delibera Assemblea Legislativa Regione Emilia-Romagna (DAL) n.112/2007). Available data mostly cover the more urbanised areas in low relief areas, such as valleys and gently dipping slopes made up of little to not-consolidated recent deposits. Remarkably less information is available from the mountainous sector of the Apennines in the South, where the highest velocities of the entire Emilia-Romagna occur. Fig. 1: V S values in the Regione Emilia-Romagna.