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North Fork Valley Seismic Network — First Quarter 2011
<br />events on 6 January at 6:14 and 6:39 GMT were M 3.0 and 2.7, respectively. The final event in
<br />this quarter recorded by the NIEC was the largest, a M 3. 1, on 17 February at 22:47 GMT.
<br />Recorded Peak Ground Accelerations
<br />PGA values are generally recorded for all triggered events on the three - component
<br />accelerometers. We have included the largest PGA recorded for each relocated seismic event in
<br />Table 3 when available, along with the station that recorded the ground motion and the event -to-
<br />station distance. The largest PGA recorded during the first quarter was 0.007 g at station MFB
<br />for the 18 February at 21:30 GMT M 1.7 event at a distance of approximately 0.92 km (0.57
<br />mi). This event occurred at the Bowie Mine. The largest PGA recorded at the West Elk Mine
<br />was 0. 000 15 g at station SPG resulting from the 21 March 22:30 GMT M 1.8 seismic event that
<br />occurred at a distance of approximately 6.76 km (4.2 mi). Note distances are approximate given
<br />uncertainties in the event locations due to uncertainties in the velocity model used in the
<br />relocations.
<br />ACKNOWLEDGMENTS
<br />The NFVSN data analysis and evaluation are jointly supported by MCC and BRL. Our thanks
<br />to Wendell Koontz, MCC Project Manager, and Jim Abshire, BRL Project Manager for their
<br />support. Our appreciation to Pete Swanson (NIOSH/CDS) for his operation and maintenance of
<br />the network. Our thanks to Melinda Lee for her assistance in the preparation of this report.
<br />REFERENCES
<br />Banfill, R., 1995, PC -SUDS Utilities, A collection of tools for routine processing of seismic data
<br />stored in the seismic unified data system for DOS (PC- SUDS).
<br />Johnson, C.E., Bittenbinder, A., Bogaert B., Dietz L., and Kohler W., 1995, EW: A Flexible
<br />Approach to Seismic Network Processing: IRIS Newsletter, v. 14, no. 2, p. 1 -4.
<br />Koontz, W., 2007, Memorandum on the West Elk Mine B Seam Bounce on November 17, 2007,
<br />2 p.
<br />Swanson, P. and Koontz, W., 2006, Measurement and analysis of mining induced seismic
<br />ground motion in the vicinity of the West Elk Coal Mine, Somerset, CO (abstract):
<br />Seismological Research Letters, v. 77, no. 2, p. 318.
<br />Swanson, P., Stewart, C., and Koontz, W., 2007, Installation of a digital, wireless, strong- motion
<br />network for monitoring seismic activity in a western Colorado coal mining region,
<br />Proceedings of the 20th Symposium on Application of Geophysics to Engineering and
<br />Environmental Problems (SAGEEP), Environmental and Engineering Geophysical
<br />Society, p. 559 -565.
<br />Wong, I.G. and McGarr, A., 1990, Implosional failure in mining- induced seismicity: A critical
<br />review, in Rockbursts and Seismicity in Mines, Proceedings of the Second International
<br />Symposium, C. Fairhurst (ed.), A.A. Balkema Publishers, p. 45 -51.
<br />WAX_WCFS \PROJECTS \WEST ELK -MTN COAL \2011 Q1 \Q1_2011_MCC.DOC \27- MAY -11\ \OAK 5
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