Laserfiche WebLink
By October, 2005, five stations of the monitoring system were in operation near the Bowie Mine <br />with a radio network transmitting most stations to the mine (near the BW K station). The additional <br />instruments were added to the network and were operational by July 1, 2006. Reconfiguration of <br />the radio network to transmit all signals to the Paonia airport took place during the third quarter of <br />2006 (July-September, 2006). During this transition period multichannel recording of data (event <br />files of more than 5 station records in one file) were obtained for 45 days out of 92 days in the <br />quarter though each individual station did record its own individual station arrivals. Portions of the <br />Earthworm computer program of the USGS are used to record the multistation data in event files. <br />To summarize the operations, individual station recordings were made for the entire period; two <br />Earthworm systems were operating from July 19 to August 18; a single Earthworm system <br />operated until August 25 and again during the period of September 13 to September 30. The <br />Earthworm systems experienced outages due to radio interference and network reconfiguration <br />activities during this period but were fully operational at the end of the quarter. At the end of <br />September the links to the data concentration site at the Paonia airport and the high-speed <br />internet connection were operational. Data were available at the Spokane offices of NIOSH for <br />daily review. <br />The following table is the correspondence of digital counts to the acceleration due to the earth's <br />gravity. Typical noise levels on the recordings are 5-15 digital counts, a figure that will decrease <br />as electronic noise sources are eliminated. Of course ground motions such as wind events, traffic, <br />and animals will continue. Multiple stations mitigate these noise sources as they typically occur on <br />one or a few stations. <br />TABLE 2 DIGITAL COUNTS vs. ACCELERATION DUE TO GRAVITY <br />DIGITAL COUNTS MICRO g <br />(10 6 of acceleration of <br />gravity) <br />25 0.75 <br />50 1.50 <br />100 3.00 <br />200 4.96 <br />1000 29.80 <br />5000 149.01 <br />10000 298.02 <br />335522 10000 1% of <br />OBSERVATIONS <br />Identification of Seismic Events Events are regarded as seismic in origin and logged by the <br />triggered recording system if they appear on two or more stations with sufficient amplitude and <br />impulsive onset. Using the triggered system, 523 events have been cataloged during the study to <br />date with 523 seismic events being identified in the third quarter of 2006.