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strata and deep cover(up to 800 in [2,600 ft]). Despite the rather large 1,100-m (3,600-ft)average
<br /> source-to-receiver distance in this aray, the regularity in seismic activity can be observed. In
<br /> general, it was found to follow closely the regularity in the fracture and deformation processes
<br /> accompanying the face.
<br /> Data in Figure 7 were acquired with a temporary network of geophones deployed on the
<br /> surface above a longwall panel at the Foidel Creek Mine near Oak Creek, CO. The 600-m (2,000
<br /> ft) diameter array was 365 m (1,200 ft) above the coal seam, yielding an average source-to-
<br /> receiver distance of 500 in (1,650 ft). Events shown were collected over an 8-day period as the
<br /> 250-m- (820-ft)wide face advanced 188 in(615-ft)from right to left(Figure 7).As many as 2,000
<br /> events per day were detected with this surface array, yielding a detection sensitivity similar to that
<br /> observed with panel-wide underground networks. The automated processing procedures
<br /> implemented in the field resulted in 500 to 1,000 well-located events per day. The elongate
<br /> distribution of seismic activity outside the active panel is a feature that is the subject of additional
<br /> study. Three-dimensional models of the seismic velocity structure are being constructed to assist
<br /> in the data processing and interpretation.
<br /> SUMMARY
<br /> An automated seismic data acquisition and processing system has been developed by NIOSH for
<br /> use in mine safety studies. Several systems utilizing a distributed PC computing environment have
<br /> been constructed and deployed in hard-rock, coal, and underground stone mines for testing and
<br /> applications. System flexibility is derived from its distributed nature, compatibility with multiple
<br /> A/D converters and operating systems, and user control over the automated processing. These
<br /> systems are now being applied in studies designed to reduce hazards associated with roof falls,
<br /> rock bursts,coal bumps,and mine collapse.
<br /> ACKNOWLEDGMENTS
<br /> This work would not have been possible without the assistance and cooperation of Silver Valley
<br /> Resources, Twentymile Coal, Plateau Mining, and Bowie Resources. Special recognition is given
<br /> to Butch Sines,Rocky Thompson,Andy Schissler,John Mercier,and Greg Hunt for their time and
<br /> assistance. A number of software modules used in the development of this system were authored
<br /> and/or modified by R. Banfill, F. Boler, D. Dodge, and L. Estey. NIOSH employees K. Heasley,J.
<br /> Marshall, C. Colton, J. Ellenberger, and P. Jeran made critical contributions in the deployment
<br /> at the Willow Creek Mine. C. Sunderman developed amplifiers and filter units used in some of the
<br /> applications. P. Santerre, T. Geiger, and F. Boler provided critical assistance with the
<br /> measurements at Foidel Creek.
<br /> REFERENCES
<br /> Banfill, R., 1996, PC-SUDS utilities: A collection of tools for routine processing of seismic
<br /> data stored in the Seismic Unified Data System for DOS(PC-SUDS),version 2.5.
<br /> Ellenberger, J., Heasley, K., Swanson, P., and Mercier, J., 2001, Three-dimensional
<br /> microseismic monitoring of a Utah longwall. In Rock Mechanics in the Public Interest.
<br /> Proceedings of the 38th U.S. Rock Mechanics Symposium, DC Rocks, ed by D. Elsworth, J.P.
<br /> Tinnucci,and K.A. Heasley(Washington,D.C.,July 7-10, 2001). Balkema,pp. 1321-1326.
<br /> Gibowicz, S.J., Lasocki, S., eds. 1997, Rockbursts and Seismicity in Mines, Proceedings of the
<br /> 4th International Symposium on Rockbursts and Seismicity in Mines, ed. by S. J. Gibowicz and S.
<br /> Lasocki(Kracow,Poland,Aug. 11-14, 1997). Balkema, 437 pp.
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