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strata and deep cover (up to 800 m [2,600 ft]). Despite the rather large 1,100-m (3,600-ft) average
<br />source-to-receiver distance in [his a7ay, the regulazity 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 [he face.
<br />Data in Figure 7 were acquired with a temporary network of geophones deployed on the
<br />surface above a longwall panel at [he Foidel Creek Mine near Oak Creek, CO. The 600-m (2,000
<br />ft) diameter arzay was 365 m (1,200 fr) above the coal seam, yielding an average source-to-
<br />receiver distance of 500 m (1,650 ft). Events shown were collected over an 8day period as the
<br />250-m- (820-ft) wide face advanced 188 m (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. Threedimensional 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 fortes[ing 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 />ACKNO W LEDCMENTS
<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 [his 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. Conpton, J. Ellenberger, and P. Jeran made critical contributions in the deployment
<br />at the Willow Creek Mine. C. Sunderman developed ampli5ers and filter units used in some of [he
<br />applications. P. San[erze, 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 [he Seismic Unified Data System for DOS (PC-SUDS), version 2.5.
<br />Ellenberger, 1., 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 Svmposium, OC Rocks, ed by D. Elsworth, J.P.
<br />Tinnucci, and K.A. Heasley (Washington, D.C., July 7-1Q, 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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