Infrasound Detection of Large Mining Blasts in Kazakstan

摘要

Since October, 1997, we have recorded infrasound signals at Kurchatov, Kazakstan, from large mining blasts in Kazakstan and the Altay-Sayan region, Siberia. Kurchatov is an ideal site for research on infrasound and application of synergistic (seismic and acoustic) methods of event discrimination. This is because it operates a 21-element short-period seismic array and a three-component broadband seismographic station and because of its close proximity to large (100+ ton) mining operations. Several large mines in the region routinely carry out large explosions that are detected seismically and with infrasound. The mines range in distance from 80 to 750 km from the infrasound array. The Ekibastuz mine, 250 km west of the array, regularly produces 4-6 seismic detections per day. The corresponding number of infrasound detections is found to be dependent upon the season and the local winds. During the winter months, when the direction of the zonal component of the stratospheric wind is from west to east, a strong stratospheric duct develops between Ekibastuz and Kurchatov and the number of infrasound detections is high. During this period the infrasound signal consists of two arrivals separated by about 60 s. A preliminary interpretation of these signals is that the first arrival at 250 km distance propagates through the troposphere and is followed 60 s later by a stratospheric arrival. During the summer months, when the zonal winds reverse direction, the number of infrasound detections is low. In March 1999, we installed a three-element infra sound array with about 2-km sensor spacing at Kurchatov. Two of the elements consist of Globe microphones connected to noise-reduction hose and pipe arrays, while the third is actually a small array comprised of several Soviet-built, low-frequency microphones (K- 301A) connected to various noise-reducing pipe configurations.