On the evening of 10 April 2013 (MDT) a massive landslide occurred at the Bingham Canyon copper mine near Salt Lake City, Utah, USA. The northeastern wall of the 970-m-deep pit collapsed in two distinct episodes that were each sudden, lasting ~90 seconds, but separated in time by ~1.5 hours. In total, ~65 million cubic meters of material was deposited, making the cumulative event likely the largest non-volcanic landslide to have occurred in North America in modern times. Fortunately, there were no fatalities or injuries. Because of extensive geotechnical surveillance, mine operators were aware of the instability and had previously evacuated the area. The Bingham Canyon mine is located within a dense regional network of seismometers and infrasound sensors, making the 10 April landslide one of the best recorded in history. Seismograms show a complex mixture of short-and long-period energy that is visible throughout the network (6-400 km). Local magnitudes (M L) for the two slides, which are based on the amplitudes of short-period waves, were estimated at 2.5 and 2.4, while magnitudes based on the duration of seismic energy (m d) were much larger (>3.5). This magnitude discrepancy, and in particular the relative enhancement of longperiod energy, is characteristic of landslide seismic sources. Interestingly, in the six days following the landslide, 16 additional seismic events were detected and located in the mine area. Seismograms for these events have impulsive arrivals characteristic of tectonic earthquakes. Hence, it appears that in this case the common geological sequence of events was inverted: Instead of a large earthquake triggering landslides, it was a landslide that triggered several small earthquakes.

A large and tragic underground collapse occurred in the Crandall Canyon coal mine in eastcentral Utah on 6 Aug 2007, causing the loss of six miners and attracting national attention. This collapse was accompanied by a local magnitude (M L) 3.9 seismic event having a location and origin time coincident with the collapse, within current uncertainty limits. Two lines of evidence indicate that most of the seismic wave energy of this event was generated by the mine collapse rather than a naturally-occurring earthquake: (1) the observation that all of the observed P-wave first motion directions are down and (2) the results of a moment tensor inversion by Ford et al. (2008). We propose one possible model for the collapse that has dimensions of 920 m E-W by 220 m N-S and an average roof-floor closure of 0.3 m. This model is consistent with the seismic moment, volumetric constraints on the amount of closure, available underground observations, and our best location for the M L 3.9 epicenter. This epicenter is near the western end of our proposed collapse area, suggesting that the collapse propagated mostly eastward from its initiation point. Our locations for the M L 3.9 event and for other seismic events that occurred in the area before and after it were greatly improved by the use of a double difference method and data from a 5-station temporary network that the University of Utah deployed near the mine beginning on 8 Aug. 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 2 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 data processing for the University of Utah regional seismic network: 8 in the 2.5-week period prior to the collapse (M L ≤ 1.9) and 15 during an earlier period of activity in late February and early March (M L ≤ 1.8). These events occurred primarily in areas where there was concurrent or recent mining activity. By the end of August, the 6 Aug collapse had been followed by 37 locatable seismic events of M L ≤ 2.2, which clustered near the eastern and inferred western ends of the collapse area. One of these "aftershocks" (M L 1.6) occurred in conjunction with the violent burst of coal from the mine walls on 17 Aug (UTC) that killed three rescuers and injured six others. 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. However, there was a noteworthy 5.8-day hiatus in activity, above a completeness threshold of coda magnitude (M C) 1.6, that began 37 hours after the collapse.

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Master event and double-difference techniques were used to relocate mining-induced seismicity (MIS) at the Trail Mountain Mine, a longwall coal mine in central Utah. Travel-time data were collected by Arabasz et al. (2002) using a surface seismic network with stations at elevations both above and below mine level (because of the topography) and a single in-mine station. Arabasz et al. (2002) only used surface stations above mine level to determine locations. Using this network geometry, they were only able to constrain focal depths for 321 of 1829 events. In contrast, we use all stations, creating a 3D network. Hypocentral locations are improved by implementing a master event methodology to reduce the effects of uncertainties in the velocity structure, though the resulting locations do not correspond with known structures or stratigraphy. The mismatch between the locations and geology is likely due to fracturing of the rock mass by the mining process, thereby decreasing the seismic velocity near mined-out regions. Assuming a 10% velocity decrease places the MIS in the roof of the mine. A double-difference procedure is used to mimic a timevarying velocity structure. The time-varying velocity structure results in locations that approximate the dip of the coal seam. By using all available stations and allowing for a time-varying velocity structure, we find the MIS is located immediately above the coal seam and closely follows the position of the coalface. The epicenters align with the roads along the longwall panel, where stress concentrations are expected during mining.Online Material: Animations of the progression of seismicity along the longwall panel.

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