Power spectra of quarry blasting works measured in different depths

manifestation of technical seismicity. Comparative measurements of
vibrations from blasting generated in open-pit mines were performed
in the Jeroným Mine near Čistá (Czech Republic). A detailed
evaluation of vibrations on underground spaces is very important here
because this mine is a significant heritage site of medieval tin mining.
The distance between the nearest feldspathic quarry named Krásno
and the Jeroným Mine is 4.7 km east, Vítkov quarries (granite)
is located north in the distance of 6.3 km. Maximum values from
the nearest quarry Krásno are usually within the range of
10-3 – 10-2 mm.s-1. Prevailing frequency range of recorded waves is
1 - 6 Hz for both quarries.
To qualify seismic loading of mine, one seismic station was located on
the surface, the second one in the mine at a depth of about 30 m.
Power spectra could be used for distinguishing, but the difference in
spectra shapes is rather evident. Especially the difference is most
explicit for the frequency range 70 - 100 Hz between power spectra of
surface and underground records. Fitted trends were calculated for the
mentioned frequency range of power spectra. Spectral time-frequency
diagrams were also defined.