Source Characterization of the 6 August 2007 Crandall Canyon Mine Seismic Event in Central Utah

On August 6, 2007 a local magnitude 3.9 seismic event occurred at 08:48:40 UTC in central Utah. The epicenter is within the boundaries of the Crandall Canyon coal mine (c.f. Pechmann et al., this volume). We performed a moment tensor analysis with complete, three-component seismic recordings from stations operated by the USGS, the University of Utah, and EarthScope. The analysis method inverts the seismic records to retrieve the full seismic moment tensor, which allows for interpretation of both shearing (e.g., earthquakes) and volume-changing (e.g., explosions and collapses) seismic events. The results show that most of the recorded seismic wave energy is consistent with an underground collapse in the mine. We contrast the waveforms and moment tensor results of the Crandall Canyon Mine seismic event to a similar sized tectonic earthquake about 200 km away near Tremonton, Utah, that occurred on September 1, 2007. Our study does not address the actual cause of the mine collapse.