Following closure of the U.S. Bureau of Mines, Congress transferred responsibility for health and safety research in mining to the National Institute for Occupational Safety and Health (NIOSH). NIOSH has developed a personal-computer-(PC-)based seismic data acquisition and processing system for use in studies designed to reduce hazards associated with rock bursts, coal bumps, mine collapse, and other catastrophic mine failures. The system design has its roots in IASPEI PC-based systems (Lee 1989, 1994) using the PC-SUDS data format. Design requirements include (i) low-cost, off-the-shelf, data acquisition and computer hardware, (ii) the capability of automatically merging waveform data sets from different types of monitoring systems, (iii) delivery of raw and processed data underground, on the surface, as well as to remote sites, and (iv) automated data collection and processing over long periods of time without the need for human intervention. Current installations utilize multiple, autonomous seismic networks located both underground and on the surface, providing 20 to 35 stations within a I-km radius. In underground networks, accelerometer and/or velocity signals are digitized at a sampling rate of 1000 samples per second (SPS) using a Symmetric Research A/D converter attached to a local data acquisition PC. In surface systems, NIOSH-designed three-channel A/D units are used to digitize signals continuously at remote stations at rates up to 1000 SPS. Multiple spread-spectrum radio links continuously transmit data in the U. S. Geological Survey's digital telemetry format back to a centralized processing PC equipped with a multichannel serial port board. Fiber-optic networks connect surface and underground data acquisition and processing PCs. Waveform files are collected either in trigger-capture mode or continuously and are automatically time corrected, merged, and processed in batch mode. Event locations, magnitude estimates, and other processed data are distributed for display and analysis on network nodes both underground and in the offices of mine engineers and mine managers. In this paper, results are presented from installations in both hardrock and coal mines.
P. L. Swanson, National Institute for Occupational Safety and Health, Spokane Research Lab, Spokane, WA 99207, USA