ABSTRACT
Nine tri-axial borehole accelerometers were installed in Precambrian quartzite (typical Young’s modulus of 70 GPa) within 200 m along a haulage tunnel 2650 m deep in Western Deep Levels gold mine in South Africa. From February to October 1996 more than 25 thousand seismic events were recorded with a sampling frequency of 15 kHz and a dynamic range of 120 dB. Among those events, ~ 40 events (108 < seismic moment M o < 1012 Nm) were picked up, which were beautifully recorded by all stations, had least coda and significant S-phases. The hypocentral distance ranged from several ten m to ~ 1 km. Q is estimated by assuming the ω-2 model is a good approximation of source displacement spectrum. Q ranged from 20 to 300. Small Q was caused by paths adjacent to mined area and large Q longer paths in solid rock. Corner frequency (f o) of P-wave with Q-correction ranged from 70 to 1800 Hz. M o was inversely proportional to the cubed f o (the cubic law was upheld), being consistent with other studies that cover narrower frequency- and dynamic- ranges. However, another analysis of our data with limited bandwidths (– 1 kHz) also results in the cubic law, although f o is systematically low. This suggests that the cubic law it-self cannot always be a proof of good data or correct data processing.
