Speaker
Description
Geophysical investigations and studies on the local seismic noise are of paramount importance for evaluating the candidate locations for hosting Einstein Telescope (ET), the third-generation gravitational wave detector. In the Italian candidate site, several active and passive geophysical acquisitions have been carried out over the last years. The main objective of the recent analysis is the characterization of the noise wavefield. In this work, we present the results from four temporary seismic arrays installed in different portions of the Italian candidate site, each with different geometrical layouts, recording durations, and total numbers of stations. We will show some preliminary results from the latter deployed in spring 2026, with a 2000 m aperture for targeting the noise seismic field in the 1-10 Hz. The recordings confirm the exceptionally low level of seismic noise approaching Peterson's New Low Noise Model for frequencies higher than 1 Hz. We provide an overview on the seismic noise characteristics and its azimuthal distribution, obtained through beamforming. Moreover, we leverage the noise recordings to extract (i) Rayleigh wave dispersion curves using fk analysis, which are then inverted to obtain a one-dimensional, shear-wave velocity model of the subsurface and (ii) HVSR spectra across all arrays' stations. With these arrays we could reconstruct the seismic wavefield in the entire 1-20 Hz frequency range. The inversion of dispersion curves in the same frequency range highlighted a rather homogeneous, high-velocity terrain (VS=2–3 km/s) in the first 150 m. The flat HVSR spectra across all arrays excludes the presence of a resonant, low-velocity layer at shallow depth.