Array analysis of seismic noise at the Sos Enattos mine, the Italian candidate site for the Einstein Telescope

Gilberto Saccorotti;Carlo Giunchi;Michele D’Ambrosio;Sonja Gaviano;Luca Naticchioni;Domenico D’Urso;Davide Rozza;Alessandro Cardini;Andrea Contu;Francesca Dordei;Matteo Cadeddu;Matteo Tuveri;Carlo Migoni;Michele Punturo;Annalisa Allocca;Enrico Calloni;Giovanni Luca Cardello;Luca D’Onofrio;Nazanin Davari;Daniele Dell’Aquila;Rosario De Rosa;Massimo Carpinelli;Luciano Di Fiore;Matteo di Giovanni;Luciano Errico;Irene Fiori;Maria Concetta Tringali;Jan Harms;Soumen Koley;Vittorio Longo;Ettore Majorana;Valentina Mangano;Marco Olivieri;Federico Paoletti;Luca Pesenti;Paola Puppo;Piero Rapagnani;Massimiliano Razzano;Fulvio Ricci;Valeria Sipala;Iara Tosta e Melo and Lucia Trozzo

2023-01-01

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Abstract

The area surrounding the dismissed mine of Sos Enattos (Sardinia, Italy) is the Italian candidate site for hosting Einstein Telescope (ET), the third-generation gravitational wave (GW) observatory. One of the goals of ET is to extend the sensitivity down to frequencies well below those currently achieved by GW detectors, i.e. down to 2 Hz. In the bandwidth [1,10] Hz, the seismic noise of anthropogenic origin is expected to represent the major perturbation to the operation of the infrastructure, and the site that will host the future detector must fulfill stringent requirements on seismic disturbances. In this paper we describe the operation of a temporary, 15-element, seismic array deployed in close proximity to the mine. Signals of anthropogenic origin have a transient nature, and their spectra are characterized by a wide spectral lobe spanning the [3,20] Hz frequency interval. Superimposed to this wide lobe are narrow spectral peaks within the [3,8] Hz frequency range. Results from slowness analyses suggest that the origin of these peaks is related to vehicle traffic along the main road running east of the mine. Exploiting the correlation properties of seismic noise, we derive a dispersion curve for Rayleigh waves, which is then inverted for a shallow velocity structure down to depths of ≈≈ 150 m. This data, which is consistent with that derived from analysis of a quarry blast, provide a first assessment of the elastic properties of the rock materials at the site candidate to hosting ET.