HR: 1340h
AN: S13A-1053 [Abstracts]
TI: Preliminary Seismological Report on the 6 August 2007 Crandall Canyon Mine Collapse in Utah
AU: * Pechmann, J C
EM: pechmann@seis.utah.edu
AF: University of Utah Seismograph Stations, 135 South 1460 East Rm 705 WBB, Salt Lake
City, UT 84112-0111, United States
AU: Arabasz, W J
EM: arabasz@seis.utah.edu
AF: University of Utah Seismograph Stations, 135 South 1460 East Rm 705 WBB, Salt Lake
City, UT 84112-0111, United States
AU: Pankow, K L
EM: pankow@seis.utah.edu
AF: University of Utah Seismograph Stations, 135 South 1460 East Rm 705 WBB, Salt Lake
City, UT 84112-0111, United States
AU: Burlacu, R
EM: burlacu@seis.utah.edu
AF: University of Utah Seismograph Stations, 135 South 1460 East Rm 705 WBB, Salt Lake
City, UT 84112-0111, United States
AU: McCarter, M K
EM: k.mccarter@utah.edu
AF: Dept of Mining Engineering, University of Utah, 135 South 1460 East Rm 313 WBB, Salt
Lake City, UT 84112-0111, United States
AB:
A large and tragic collapse occurred in the Crandall Canyon coal mine in east-central Utah on 6 Aug 2007,
causing the loss of six miners and generating national attention. This collapse was accompanied by a local
magnitude (ML) 3.9 seismic event having an origin time of 2:48 am MDT (8:48 UTC) and a location near the
collapse. Two lines of evidence indicate that most of the seismic wave energy of this event was generated by the
mine collapse rather than an earthquake: (1) the observation that all of the P-wave first motion directions are
down and (2) the results of a moment tensor inversion by Ford et al. (2007;
http://seismo.berkeley.edu/seismo/Homepage.html).
The Crandall Canyon mine is in an area of Utah where there is abundant mining-induced seismicity, including
events with both collapse and shear-slip sources. Prior to the 6 Aug collapse, and within a 3 km radius of it, there
were 28 seismic events during 2007 that were large enough to be detected and located as part of the routine
processing of University of Utah regional seismic network data: 8 in the 2.5-week period prior to the collapse
(ML ≤ 1.9) and 15 during an earlier period of activity in late February and early March (ML ≤
1.8). The 6 Aug collapse was followed by 37 locatable seismic events of ML ≤ 2.2 before the end of
August. One of these "aftershocks" (ML 1.6) occurred in
conjunction with the violent burst of coal from the mine walls on 17 Aug (UTC) that killed three rescuers. The
aftershocks have an exponential frequency-magnitude distribution with a lower ratio between the frequencies of
smaller- and larger-magnitude events (lower b-value) than for the prior events in the area. Aftershock rates
generally decreased with time through August but there was a noteworthy 5.8-day hiatus in activity that began 37
hours after the collapse. The University of Utah deployed a 5-station temporary network near the mine beginning
on 8 Aug. Data from these stations are being used to help develop travel-time corrections for these and other
stations in order to improve the computed locations of seismic events that occurred in the area both before and
after the 6 Aug collapse.
DE: 7215 Earthquake source observations (1240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting