Tele-infrasonic studies of hard-rock mining explosions.
The Lac-du-Bonnet infrasound station, IS-10, and the Minnesota iron mines 390 km to the southeast are ideally located to assess the accuracy of atmospheric profiles needed for infrasound modeling. Infrasonic data from 2003 associated with explosions at the iron mine were analyzed for effects of explosion size and atmospheric conditions on observations with well-constrained ground truth. Noise was the determining factor for observation; high noise conditions sometimes prevented unequivocal identification of infrasound arrivals. Observed arrivals had frequencies of 0.5 to 5 Hz, with a dominant frequency of 2 Hz, and generally had durations on the order of 10 s or less. There was no correlation between explosive amount and observability. Tele-infrasonic propagation distances (greater than 250 km) produce thermospheric ray paths. Modeling is based upon MSIS/HWM (Mass Spectrometer Incoherent Scatter/Horizontal Wind Model) and NRL-G2S (Naval Research Laboratory Ground to Space) datasets. The NRL-G2S dataset provided more accurate travel time predictions that the MSIS/HWM dataset. PE modeling for the NRL-G2S dataset indicates energy loss at higher frequencies (around 4 Hz). Additionally, applying the Sutherland/Bass model through the NRL-G2S realization of the atmosphere in InfraMAP results in predicted amplitudes too small to be observed.
McKenna
Mihan H
MH
Structural Engineering Branch, Geotechnical and Structures Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, USA. Mihan.H.McKenna@erdc.usace.army.mil
Stump
Brian W
BW
Hayek
Sylvia
S
McKenna
Jason R
JR
Stanton
Terry R
TR
D000162:Acoustics; D001272:Atmosphere; D005107:Explosions; D055593:Geological Phenomena; D005844:Geology; D007501:Iron; D008906:Mining; D008910:Minnesota; D008962:Models, Theoretical; D009622:Noise; D015203:Reproducibility of Results; D013997:Time Factors
D007501:Iron