Changes in mining‐induced seismicity before and after the 2007 Crandall Canyon Mine collapse

Abstract

On 6 August 2007, the Crandall Canyon Mine in central Utah experienced a major collapse that was recorded as an M w 4.1 seismic event. Application of waveform cross-correlation detection techniques to data recorded at permanent seismic stations located within~30 km of the mine has resulted in the discovery of 1494 previously unknown microseismic events related to the collapse. These events occurred between 26 July 2007 and 19 August 2007 and were detected with a magnitude threshold of completeness of 0.0, about 1.6 magnitude units smaller than the threshold associated with conventional techniques. Relative locations for the events were determined using a double-difference approach that incorporated absolute and differential arrival times. Absolute locations were determined using ground-truth reported in mine logbooks. Lineations apparent in the newly detected events have strikes similar to those of known vertical joints in the mine region, which may have played a role in the collapse. Prior to the collapse, seismicity occurred mostly in close proximity to active mining, though several distinct seismogenic hot spots within the mine were also apparent. In the 48 h before the collapse, changes in b value and event locations were observed. The collapse appears to have occurred when the migrating seismicity associated with direct mining activity intersected one of the areas identified as a seismic hot spot. Following the collapse, b values decreased and seismicity clustered farther to the east.

Injection‐induced seismicity in Carbon and Emery Counties, central Utah

“…Our results of b-values of these seismic events are comparable with previous studies for the Utah mining region (Smith et al 1974;Pechmann et al 2008;Kubacki et al 2014). These calculations, however, were completed over two years or less.…”

“…Mining induced seismicity (MIS) in central Utah has been monitored by the University of Utah Seismograph Station (UUSS) regional network since 1978 (Kubacki et al . ). The MIS is mostly a result of underground mine collapse and shear‐slip motion on rock fractures (Pechmann et al .…”

“…Previous studies have attributed the area's seismicity to coal mining (Smith et al 1974;Arabasz et al 2007;Pechmann et al 2008), which has been extensive in central Utah. Mining induced seismicity (MIS) in central Utah has been monitored by the University of Utah Seismograph Station (UUSS) regional network since 1978 (Kubacki et al 2014). The MIS is mostly a result of underground mine collapse and shear-slip motion on rock fractures (Pechmann et al 2008).…”

Magnitude‐based discrimination of man‐made seismic events from naturally occurring earthquakes in Utah, USA

“…From October 2000 to April 2001, an array of 12 seismometers was installed over the Trail Mountain Mine and used to locate approximately 1900 seismic events coincident with longwall mining operations [Arabasz et al, 2005;Boltz et al, 2014]. Following the 6 August 2007 Crandall Canyon mine collapse, five seismometers were temporarily installed above and next to the mine, resulting in~1000 well-located aftershocks after application of waveform cross-correlation techniques [Kubacki et al, 2014]. These and other studies have shown that MIS in Utah occurs very close to mine level, at depths of < 2 km below the surface.…”

Exploring remote earthquake triggering potential across EarthScopes' Transportable Array through frequency domain array visualization

“…An alternative way to improve detection of small earthquakes involves waveform correlation or matched filter techniques [Kubacki et al, 2014;Zhao and Peng, 2009;Shelly et al, 2007;Shelly et al, 2013;van der Elst et al, 2013]. These methods have proven to be highly effective in recovering events, often below the noise level, where a larger event has already occurred.…”