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North Fork Valley Seismic Network - First Quarter 2008 <br />Table 1. Seismograph Stations of the North Fork Valley Seismic Network <br /> <br />Station Latitude <br />(degrees) Longitude <br />(degrees) Elevation <br />(ft) [m] Station <br />Correction <br />(sec) <br />Station Name <br />Owner <br />BWK 38.928 -107.537 6701 [2042] -0.139 Bowie King Mine BRL <br />FGH 38.948 -107.536 7201 [2195] -0.087 Freeman Gulch Hubbard BRL <br />LLM 38.857 -107.461 8240 [2512] 0.042 Lion Mesa MCC <br />MCD 38.881 -107.474 7274 [2217] -0.079 Minnesota Creek Dam MCC <br />MFB 38.956 -107.559 7924 [2415] -0.002 Middle Forest Boundary BRL <br />SPG 38.872 -107.425 8174 [2491] 0.033 South of Poison Gulch MCC <br />SEF 38.874 -107.390 8667 [2642] 0.101 South of East Flatiron MCC <br />TCR 38.982 -107.564 8483 [2586] 0.075 Terror Creek Dam BRL <br />WFW 38.901 -107.424 8433 [2570] 0.068 West Flatiron West MCC <br />WTM 38.941 -107.591 7954 [2424] 0.002 West Tower Mountain BRL <br />The development of NFVSN is described in previous reports. Real-time processing utilizes <br />modules from the Earthworm software suite developed by the U.S. Geological Survey (USGS) <br />in Menlo Park, California (Johnson et al., 1995). The program detects, automatically locates, and <br />saves event data for triggered events. The network is divided into two sub-nets (each with five- <br />stations), one in each of the two main mining areas (Figure 1). <br />DATA PROCESSING <br />Identification of Events <br />Events are regarded as seismic in origin and logged by the Earthworm triggering system if they <br />appear on five or more stations with significant amplitude, impulsive onset and appropriate time <br />differences between stations. Triggering occurs within the two sub-nets (five stations in each) so <br />that important events are not missed. Earthworm also provides automatic locations for events <br />that have sufficient arrival time picks. During the first quarter, Earthworm detected and located <br />3436 events (not all of which were seismic events). Many more triggered waveform files were <br />recorded, many of which have insufficient station data for locating the events. <br />We reviewed the daily summary or heliocorder records (these are continuous recordings of 12- <br />hour periods conveniently plotted on one page) for filtered traces at three stations (WTM, LLM <br />and WFW; Figure 1). We also reviewed the list of events automatically detected and located by <br />Earthworm. Events were chosen based on amplitudes on the heliocorder records at the three <br />um WAX_WCFS\PROJECTS\WEST ELK-MTN COAL\2008 Q1\Q1 2008 MCC_FINAL.DOC\18-MAY-08\\OAK 2