GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 beamforming (f-k) and spatal autocorrelaton (SPAC) analysis (Hailemikael et al. , 2023), using a 2D array of seismic statons, with a maximum aperture of about 880 m (Fig. 1B). We computed the Rayleigh (R) and Love (L) dispersion curves (DC) from both ( i ) the linear array of geophones, using the f-k method, and the MiniVib as actve source, and ( ii ) from the 2D array of seismic statons, using ambient vibraton three-component data, though f-k and SPAC methods. The observed dispersion and H/V curves were jointly inverted with the Geopsy tool (Wathelet et al. 2020) to obtain the 1D shear-wave velocity (Vs) profles (Fig. 2). The main result of the work is a consistent mono-dimensional Vs profle, generated by the synthesis the actve and passive methodologies, supportng the seismic stratgraphy interpretaton of the subsurface to a depth of about 700 m (Fig. 3). The regional unconformity surfaces, supportng the stratgraphic subdivision of the Quaternary successions, are associated with discrete layers of sharp increase of the seismic velocity. The strongest velocity increase is associated with the top of the P2 turbidites, at about 680 m, in perfect match with the base of the Marine Quaternary (QM) illustrated by the Emilia-Romagna Region study, as visible in Fig. 3. The 1D seismic velocity model, developed at the study site, can be extrapolated to similar syncline areas in a wider Po basin area in the fnality of seismic response analysis and microzonaton analyses. Fig. 1. (A) Depth of the Marine Quaternary top, which has been largely deformed by the ongoing compressional deformaton (map produced by the Emilia-Romagna Region Geology Survey). The investgatons site is placed on the syncline, at the south of the Casaglia High. (B) Locaton of the down-hole and of the array of seismic statons. A MiniVib as source was applied for the down-hole acquisiton, whereas the seismic statons recorded ambient vibraton data. The image background shows the Lidar generated elevaton model, depictng the depositonal fuvial ridge of the river Reno.