4:45 PM - 5:00 PM
[S02-6-02] The Results of the Local Seismic Monitoring in the Underground Baksan Neutrino Observatory
Underground Baksan neutrino observatory is located on the territory of the North Caucasus, near Tyrnyauz city. It consists of two horizontal tunnels going deep into the mountains over a distance of 4 km. The depth from the surface is approximately 2 km at the most remote point of the tunnels. Two neutrino telescope, low-noise physical laboratories and ancillary equipment are installed in the underground excavations. Since the Caucasus region is characterized by high geodynamic activity, local seismic array was deployed in the galleries of observatory. The principal aim of the array is to provide data for the assessment and monitoring of seismic hazard in the observatory. The monitoring system is installed in the most remote and the deepest part of the tunnel. The array consists of 6 vertical and one 3-component sensor Sercel L4C and has the aperture of 150 m x 370 m.
The site of observations is characterized by extremely low levels of background seismic noise. The noise level almost coincides with NLNM (Peterson, 1993) in the frequency range of 0.1 - 5 Hz. It increases slightly at higher frequencies, but remains very low. Thanks to so favorable conditions, seismic sensors detect a large number of local and regional seismic events with hypocentral distances from few hundred meters to hundreds of km. Seismic events above magnitude ML=-2 are representatively registered within the distance of 10 km. Due to high sensitivity, the monitoring system daily registers from tens to a few hundreds of weak seismic events occurring in the neighborhood of the tunnels. These events occur mainly within the two local areas. One of them is located directly under the tunnels at a depth of 1.5 km, the second - at distance from 1.5 to 4 km to northeast from the monitoring system. Most of these events have a tectonic nature, but every month registers up to several tens of events that may be associated with the processes of the movement of fluids in the rock mass
The site of observations is characterized by extremely low levels of background seismic noise. The noise level almost coincides with NLNM (Peterson, 1993) in the frequency range of 0.1 - 5 Hz. It increases slightly at higher frequencies, but remains very low. Thanks to so favorable conditions, seismic sensors detect a large number of local and regional seismic events with hypocentral distances from few hundred meters to hundreds of km. Seismic events above magnitude ML=-2 are representatively registered within the distance of 10 km. Due to high sensitivity, the monitoring system daily registers from tens to a few hundreds of weak seismic events occurring in the neighborhood of the tunnels. These events occur mainly within the two local areas. One of them is located directly under the tunnels at a depth of 1.5 km, the second - at distance from 1.5 to 4 km to northeast from the monitoring system. Most of these events have a tectonic nature, but every month registers up to several tens of events that may be associated with the processes of the movement of fluids in the rock mass