GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 Impact of long-period 1D and 3D site amplification on Probabilistic Seismic Hazard of the Po Plain sedimentary basin (Italy) C. Mascandola 1 , S. Barani 2 , D. Albarello 3,4 1 Istituto Nazionale di Geofisica e Vulcanologia (INGV), Milano (Italy) 2 Dipartimento di Scienze della Terra, dell’Ambiente e della Vita (DISTAV), Università degli Studi di Genova, Genova, Italy 3 Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente (DSFTA), Università degli Studi di Siena, Siena, Italy 4 Consiglio Nazionale delle Ricerche, Istituto di Geologia Ambientale e Geoingegneria, Rome, Italy This study focuses on the incorporation and impact of site amplification effects on the probabilistic seismic hazard analysis of the entire Po Plain (Italy), one of the widest Quaternary alluvial basins of Europe. Both 1D amplification related to stratigraphic conditions and 3D amplification due to basin effects are considered. While the former was estimated through dynamic ground-response analysis (Mascandola et al., 2021), 3D basin effects are considered through the application of an empirical correction term (Lanzano et al., 2016). To properly separate aleatory variabilities and epistemic uncertainties related to site response, a partially non-ergodic approach is used (e.g., Rodriguez-Marek et al., 2014). Results are presented in terms of hazard maps for different response periods and uniform hazard spectra for selected sites. These are discussed in relation to the known regional geological features. Finally, the sensitivity of the hazard and its uncertainty to the 1D and 3D amplification components is discussed in detail. We found that, for a return period of 475 years, neglecting basin effects produces a 30% underestimation of the seismic hazard in the long-period (> 1s) range, with a significant underestimation (up to 80%) of the epistemic uncertainty. Therefore, such 3D basin effects deserve special attention in future probabilistic seismic hazard analysis in the Po Plain sedimentary basin. References Lanzano G., D’Amico M., Felicetta C., Puglia R., Luzi L., Pacor F., and Bindi D.; 2016: Ground‐motion prediction equations for region‐specific probabilistic seismic‐hazard analysis. Bulletin of the Seismological Society of America, 106(1), 73-92, doi: 10.1785/0120150096.