A Study of Mine Blasts and Rockbursts in the Pacific Northwest

• Main Authors: Rohay, Alan, Goodwin, Shannon
• Format: Report
• Language: English
• Subjects: ARMS CONTROL; BLAST WAVES; COAL MINES; COLUMBIA RIVER; CTBT(COMPREHENSIVE TEST BAN TREATY); EARTHQUAKES; Government and Political Science; IDAHO; Mining Engineering; MONITORING; NUCLEAR EXPLOSION DETECTION; NUCLEAR EXPLOSION TESTING; Nuclear Weapons; PACIFIC NORTHWEST(UNITED STATES); REFRACTION; ROCK BURSTS; SEISMIC DETECTION; Seismic Detection and Detectors; SEISMIC DISCRIMINATION; SEISMIC WAVES; SEISMOGRAPHS; SEISMOLOGICAL STATIONS; Seismology; SPECTRUM ANALYSIS; SYMPOSIA; TEST BAN TREATIES; TREATIES; UNDERGROUND EXPLOSIONS; VERIFICATION; WASHINGTON(STATE)

We have collected regional broad-band and densely-spaced short-period data for nearly 40 mining explosions from the Centralia mine, from two rockbursts in northern Idaho, and from several other explosions in the Columbia River Basalt and elsewhere in Washington state. These recordings, for events with magnitude 2.5 or larger, are being analyzed to determine the characteristics of the seismic signals that identify these events as explosions or rockbursts. The type of delayed blasting at the Centralia mine may not be conducive to the detection of spectral scalloping or nulling, and this effect has not been clearly observed in preliminary spectral analyses of the regional seismic signals. However, these and other blasts generate relatively high-amplitude Rayleigh waves (Rg) that allow their identification as explosions at close distances. We are planning to make near-field deployments using broad-band, high-frequency seismic systems to characterize the effect of the delay pattern and charge sizes on the generation of regional seismic phases from the explosions at Centralia. Rockbursts from the northern Idaho region are due to implosional and fault-slip mechanisms, as determined from in-mine seismic systems. Such events are often triggered by the failure of pillars, in some cases during de-stressing operations. Such events may be of particular interest to discrimination researchers. We are preparing to arrange for the recording of Centralia coal mine blasts on a USGS refraction line in September. Several hundred portable recorders will be operated along a 400 km profile that passes within 20 km of the Centralia mine. This will provide a comparison of the delay-fired mine blasts to the single-shot USGS explosions. This article is from 'Proceedings of the Annual Seismic Research Symposium on Monitoring a Comprehensive Test Ban Treaty (17th) Held in Scottsdale, Arizona on 12-15 September, 1995', 1996 0607 035, p572-580.