Characterization of the energy spectral density for a potash mine

Monitoring seismic activity in mines, produced by high stress faults in the vicinity of mining operations, is an important issue for mine planning. A seismic event produces a short-time duration acoustic pressure wave that travels through the rock. This low-energy seismic activity in mines is typically referred to as micro seismic events. The location of a micro seismic event is very important for mine planning since these events indicate unstable areas. Their location can be estimated using the pressure wave signals recorded at a set of sensors distributed throughout the mine. One method of localization searches over a grid of hypothesized source locations to find the one that best explains the observed measurements. The expression for the variance of error of this method depends upon the energy spectral density of the sensor signal. It is, therefore, important to have an estimate of the actual energy spectral density from sensor signals taken in the mine. This paper presents the results of the characterization of the energy spectral density using one year of data, which is approximately 2000 micro seismic events, taken from a potash mine near Saskatoon. Only signals which are closer than 2000 ft to the event source are analyzed.