How quiet is the site of the former Sos Enattos mine in Lula, Nuoro, Italy's candidate to host the future Einstein Telescope gravitational wave observatory?
Since the end of July, a research group from the Gran Sasso Science Institute, composed of Jan Harms, Tomislav Andric and Ilaria Caravella (with the collaboration of Matteo Di Giovanni, now at Sapienza University of Rome), has installed four microphone stations to measure noises around the site, in particular those that could create problems or limit the sensitivity of the most powerful instrument ever built to capture gravitational waves, almost reaching back to the Big Bang that gave birth to the universe.
"It is known that these effects are greater on the surface, while they tend to attenuate underground - the experts explain in an article published on ET Italia - the main objective of the experiment is to understand at what depth the Einstein Telescope should be built to make this source of noise negligible. The central station, equipped with two microphones, is also able to evaluate the impact of the wind on the measurements".
Also in July, a group of researchers from the Sar-Grav laboratory (composed of Domenico D'Urso of the University of Sassari and Davide Rozza and Davide Ferioli of the University of Milano-Bicocca and Infn) installed some seismometers to characterize the seismic noise in the possible vertices of ET, both in the hypothesis that the project is realized with a triangular or L-shaped geometry. The absence of noise and seismic phenomena is an important factor in understanding where to realize the ET since Italy must face competition from the Netherlands which has put forward the candidacy to host the instrument.
On paper, Sos Enattos has an advantage precisely because of the silence of the chosen location: it is in fact located in a sparsely populated area with low seismic noise, due to the fact that Sardinia is not connected to the most active tectonic zones and therefore is not affected by seismic phenomena and deformation of the earth's crust. The Dutch site, on the other hand, is located in a more populated area, on the border between the Netherlands, Belgium and Germany.
