GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.2 GNGTS 2024 Mapping seismostraHgraphical amplificaHon effects at regional scale from geological data N. Carfagna 1 , P. Pieruccini 2 , P. Fantozzi 1 , D. Albarello 2,3 1 Department of Physical Science, Earth and Environment, University of Siena, Siena, Italy 2 Department of Earth Science, University of Turin, Turin, Italy 3 Consiglio Nazionale delle Ricerche, Is9tuto di Geologia Ambientale e Geoingegneria, Rome, Italy It is widely recognized that the amplificaCon of ground moCon during earthquakes is abributed to the interference of seismic waves trapped between the free surface and impedance contrasts in the shallow subsoil. Seismic MicrozonaCon (SM) studies are devoted to evaluaCng these site effects, but their applicaCon in wider contexts is a hard and expensive task. To esCmate seismic site effects at regional scale, the most viable approach is to uClize detailed geological and geomorphological data (1:10.000-1:50.000), which are available for a large part of Italy. In the frame of the naConal research project “SERENA”, in this study a procedure is proposed and tested to constrain the enCty of 1D seismostraCgraphical ground moCon amplificaCon based on geological informaCon at the most detailed scale available. In parCcular, amplificaCon factors are esCmated for Seismically Homogeneous Microzones (SHM) defined on the basis of geological informaCon. Each SHM is represented as a stack flat homogeneous layer, each characterized in terms of engineering-geological units by following the seismic microzonaCon standards ( Commissione Tecnica, 2018; SM Working Group, 2015 ). Seismic properCes of each layer (shear waves velocity, density, damping and G/G0 curves) and respecCve range of variability are determined on the basis of the most recent literature ( Romagnoli et al., 2022 ; Gaudiosi et al., 2023 ). This informaCon feeds a linear equivalent numerical approach and the Inverse Random VibraCon Theory ( Koske and Rathje, 2008 ) to compute the expected seismic response at each SHM. To account for the relevant uncertainty, 100 random profiles were generated for each SHM, which were compaCble with available data. Outcomes of the relevant numerical simulaCons were considered to assess uncertainty affecCng amplificaCon esCmates at each SHM. Through this procedure, approximately 4000 Seismically Homogeneous Microzones were idenCfied, distributed across over 80,000 formaCon outcrops mapped on Geological map of Tuscany Region, selected by dedicated ArcgisPro TM /Arcpy TM scripts elaborated for this aim. The 50th percenCle of the amplificaCon factor (AF) distribuCon for each SHM was taken into consideraCon. This process aimed to create a new map of amplificaCon factors for the enCre territory of Tuscany, achieving an opCmal spaCal resoluCon of 1:10,000. To assess the reliability of the results obtained from numerical simulaCons, and evaluate the possible presence of biases, outcomes of the numerical procedure here considered were