2007-01-09_REPORT - C1980007 - Laserfiche WebLink

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INTRODUCTION This report is prepared by David Butler, Senior Geophysicist, MicroGeophysics Corporation, Wheat Ridge, Colorado, in partial fulfillment of a commitment by Mountain Coal Company (MCC) to monitor seismicity (including the microseismic activity near longwall mining activity) in the North Fork Valley just east of Paonia, Colorado. This commitment is to the Colorado Division of Natural Resources, Division of Reclamation, Mining and Safety. The area encompassed extends east-west from Coal Creek Mesa to West Tower Mountain and north-south from Terror Creek Reservoir to Lion Mesa (see Figure 1). The area includes the Mountain Coal Mine operated by Arch, Inc. and the Bowie No. 2 Mine property of Bowie Resources, LLC(BRL). Seismicity from the Elk Creek mine owned by Oxbow Mining, Inc. is also recorded. This report contains preliminary analyses of data collected in the third quarter of 2006, i.e. from.. July to September, 2006. Stations in the network operated previous to this quarter, but this report contains only information about the third quarter of 2006. Seismological aspects of the analysis are not yet completed. The velocity model, a ground-motion attenuation model and network magnitude definitions. are under construction. This report focuses on progress towards seismologic conclusions completed during the analysis period. The seismic monitoring program was designed to monitor seismicity levels, provide locations for local events, measure ground motion quantitatively, determine focal mechanisms when feasible, and establish the ground motion regime that structures within the network are and will be subject to during mining. OPERATIONS Station Locations and Descriptions A multi-station seismic array (10 stations) was installed by a cooperative effort of MCC and BRL and the Spokane Research Laboratory of NIOSH/CDC (National Institute for Occupational Safety and Health/Centers for Disease Control and Prevention). Station locations were determined by consideration of access, permission of landowners, spec array geometry, radio line-of-sight to the common recording site (the Paonia Airport) or a repeater station and uniform coverage of the target area (see Figure 1). The 4ocation of stations presently operating are shown on Figure 1 and corresponding station coordinates are listed in Table 1. Table 1 STATION IDENTIFIER LATITUDE LONGITUDE ELEVATION NAME OF STATION OWNER (feet) BWK 38.928 107.537 6701 Bowie Fling Mine BRL FGH 38.948 107.536 7201 Freeman Gulch Hubbard BRL LLM 38.857 107.461 8240 Lion Mesa MCC MCD 38.881 107.474 7274 Minnesota Creek Dam MCC MFB 38.956 107.559 7924 Middle Forest Boundary BRL SPG 38.872 107.425 8174 South of Poison Gulch MCC SEF 38.874 107.390 8667 South on East Flatiron MCC TCR 38.982 107.564 8483 Terror Creek Dam BRL WFW 38.901 107.424 8433 West Flatiron West MCC WTM 38.941 107.591 7954 West Tower Mountain BRL