Blasting activity of the mining industry in the United States
- Lamont-Doherty Earth Observatory, Palisades, NY (United States)
About 2 megatons of chemcial explosives are used annually in the U.S., principally in mining for coal and metal ores. Most of this explosive is used in surface mines rather than underground mines. On a typical work day there are about 30 explosions greater than 50 tons, including one shot greater than 200 tons. Shots in underground mines are typically much smaller, because of safety considerations. Almost all chemical explosions above 1 ton in the U.S. are ripple-fired and almost all above 10 tons are also shallow. Almost all are intended to break rock or to remove overburden, and are therefore very inefficient, relative to contained single shots, in generating seismic signals at regional ore teleseismic distances. These attributes make explosions used in industry quite different from the Non-Proliferation Experiment. There is very little correlation between the total amount of explosive used in a ripple-fired blast, and the seismic magnitude. Statistics on blasting magnitudes are of interest in the context of monitoring network. There is a blast reported with regional (or duration) magnitude 3.5 or above, in the U.S., a few tens of times a year; but it would appear that the teleseismic magnitude (m{sub b}) of such events are significantly lower than 3.5. Only about 10 to 30 chemical explosions per year in the U.S. are detected teleseismically with m{sub b}>3. Methods of routinely discriminating most chemical explosions from other seismic sources use spectra of regional phases at frequencies up to about 30 Hz, which is significantly higher than frequencies needed for recording teleseismic signals. The best discriminants appear to be the high-frequency spectral ratio of waves with P-wave energy (e.g. Pn or Pg) to waves with S-wave energy (Sn or Lg); and the use of spectrograms, which can be particularly useful in identifying ripple-firing.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- OSTI ID:
- 95983
- Report Number(s):
- CONF-9404100-; ON: DE95011413; TRN: 95:005144-0003
- Resource Relation:
- Conference: Symposium on the non-proliferation experiment results and implications for test ban treaties, Rockville, MD (United States), 19-21 Apr 1994; Other Information: PBD: [1994]; Related Information: Is Part Of Proceedings of the symposium on the Non-Proliferation Experiment (NPE): Results and implications for test ban treaties; Denny, M.D.; Stull, S.P. [eds.]; PB: 599 p.
- Country of Publication:
- United States
- Language:
- English
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