Then, we briefly describe the spectral properties of the seismic noise, and proceed with wavefield decomposition via slowness analysis. The paper is structured as follows: first, we introduce the study area and the array experiment. In this paper, we make use of a short-period seismic array deployed in proximity of the Sos Enattos mine, to characterize the seismic noise wavefield and to identify its main sources. Above 3 Hz, the spectra of seismic noise reflect the action of both anthropogenic and natural (mostly wind) sources. In brief, results from this latter study indicate that up to a frequency of \(\approx\)3 Hz, the main contribution to seismic spectra is that of oceanic microseisms, generally associated with wave climate in the Mediterranean Sea and, occasionally, in the North Atlantic Ocean during strong storms. The most recent work analyzes the long-term temporal variation of the seismic noise at Sos Enattos. For that same frequency range, the analysis of the underground data highlighted a temporal variability typical of human activity. These results show that the Sos Enattos mine, in the Hz frequency band, is classified within the 10% quietest sites among the more than 450 stations present in the database of the Incorporated Research Institutions for Seismology (IRIS). Previous seismological studies of the Sos Enattos site have been presented in and.
#Motion array code#
Starting from October 2019, the station located at a depth of 111 m below the surface became part of the networks managed by INGV with the station code SENA ( ). Successively, another seismometer was added to the local network at 160 m below the surface, and all the installations were consolidated. Within this framework, the Italian National Institute for Geophysics and Volcanology and National Institute for Nuclear Physics (hereinafter referred to as INGV and INFN, respectively) installed three broadband seismometers, one on the surface and the other two at different depths within the principal gallery of the mine. Site characterization, with particular reference to seismic disturbances, is thus a necessary step for assessing the potential scientific output of the infrastructure. Therefore, geodynamical stability and paucity of human activities are of paramount relevance for the evaluation of candidate sites for the construction of ET.
One of the goals of ET is to extend the frequency band of ground-based GW observations down to the Hz interval, where the detector sensitivity can be largely affected by ground vibrations of either natural or anthropogenic origin. Located in the eastern sector of central Sardinia, Italy, the area surrounding the dismissed mine of Sos Enattos is the Italian candidate site for hosting Einstein Telescope (ET), the third-generation gravitational wave (GW) observatory. 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. 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 \(\approx\) 150 m. 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. Superimposed to this wide lobe are narrow spectral peaks within the Hz frequency range. Signals of anthropogenic origin have a transient nature, and their spectra are characterized by a wide spectral lobe spanning the Hz frequency interval.
In this paper we describe the operation of a temporary, 15-element, seismic array deployed in close proximity to the mine. In the bandwidth 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. One of the goals of ET is to extend the sensitivity down to frequencies well below those currently achieved by GW detectors, i.e. 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.
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