Seismic noise background in the Baksan Neutrino Observatory

In this paper, we report a study of the seismic noise measured in the underground Baksan neutrino observatory in the framework of the site qualification for third generation Gravitational Wave detectors like the Einstein Telescope (Einstein gravitational wave telescope conceptual design study, ET-0106C-10. http://et-gw.eu/etdsdocument, 2011) and Cosmic Explorer (https://cosmicexplorer.org/). The main spectral feature below 1 H z is the oceanic microseism, while for greater frequencies the measured horizontal and vertical accelerations approach the Peterson low noise model. Using two synchronized seismometers, we also studied the coherence in the microseismic band (0.1–0.5Hz) between three underground stations located at 0.3 km, 1.4 km and 3.7 km from the tunnel entrance. Finally, on the base of our measurements, we evaluate the Newtonian noise contribution from the seismic noise background of body waves.