Comparison of Single-Fired and Delay-Fired Explosions at Regional and Local Distances,
A wide range of blasting practices are utilized by the U.S. mining industry resulting in dramatically different local and regional seismic signatures. This variability in blasting and resulting seismograms suggests that no single discriminant may be appropriate for identifying this class of sources. A range of blasting styles are identified in this paper and the distinguishing characteristics at regional distances are determined. The blasting styles are quantified with the help of mining company records and close-in acoustic,seismic and video graphic data. The regional data consists of portable deployments of high frequency and broadband sensors as well as data from the International Monitoring System Primary Array at Pinedale, Wyoming. Critical to the success of this study is the comparison of regional data from the mining explosions to data from contained, single-fired explosions. Two types of single-fired explosions are utilized, the first a calibration explosion (8 vertical boreholes with 5,000 lbs of explosives each) fired simultaneous. The second, single-fired explosion consists of a number of boreholes detonated simultaneously in the mine for the purpose of pre-splitting the material (driving fractures between boreholes) prior to a large cast shot. Data from these explosions provide the basis for identifying the source signatures of the more typical delay-fired explosions. At high frequencies the single-fired and delay-fired explosions exhibit very similar waveforms at regional distances.Both event types show a high P/L{sub g} ratio at the highest frequencies with L{sub g} dominating at lower frequencies. Mining explosions that cast material show an enrichment in surface wave energy at relatively long periods of 4-12 seconds. Timing anomalies are identified in a high percentage of mining explosions designed to cast material. The accidental, simultaneous detonation of a number of boreholes has been observed in 2 of 9 carefully instrumented cast blasts. These produce regional waveforms that can have characteristics of a single-fired explosion. Spectral scalloping is observed from some delay-fired explosions while not from others. The existence of these characteristics is dependent on the exact delay pattern utilized. Data from a single- fired explosion allows the assessment of local receiver effects that might appear as a characteristic of delay-firing. 9 figs.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 618161
- Report Number(s):
- LA-UR-97-2646; CONF-970967-; ON: DE98000600; CNN: Contract W-7405-ENG-36; TRN: AD-A332 17
- Resource Relation:
- Conference: Research symposium on monitoring a comprehensive test ban treaty, Orlando, FL (United States), 23-25 Sep 1997; Other Information: DN: Prepared in collaboration with Southern Methodist Univ., Dallas, TX.; PBD: [1997]
- Country of Publication:
- United States
- Language:
- English
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