The Apatity seismic/infrasonic array is one of the main infrasonic installations available in northern Europe. The infrasonic component is a small-aperture microbarographic array installed in conjunction with the seismic array near lake Imandra in the Kola Peninsula, with data digitized at the array site and transmitted in real time to a processing center in Apatity. A total of three infrasound sensors are installed in the innermost ring of the array, forming a triangle of approximately 500 m diameter. The sensors are differential microbarographs of model K-304-AM. The frequency working range is 0.01-10Hz, and the sensitivity is 37.5 mV/Pa.
Geometry of the combined Apatity seismic/infrasound array.
Furthermore, it has been found that ARCES, which is a seismic array and was constructed without any infrasonic instrumentation, has turned out to be quite sensitive to infrasound signals, and has been useful in our studies of infrasound waves.
ARCES configuration.
In addition to Apatity and ARCES, NORSAR has access to the data from the Swedish Infrasound Network, which has been in operation since the beginning of the 1970s. Operated by the Swedish Institute of Space Physics, the network has until recently comprised four infrasound stations: Kiruna, Jamton, Lycksele and Uppsala. The station in Uppsala was moved to Sodankyla, Finland, during the summer of 2006. The arrays in this network are triangular, with a distance between sensors of only 75 meters.
Current Nordic infrasound network, along with two explosion sites.
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