Deadly Mine 'Bump' was Recorded as Seismic Event

Aug 17, 2007

The University of Utah Seismograph Stations recorded a magnitude-1.6 seismic event at the time of a Thursday, Aug. 16 "bump" that killed and injured rescuers at a Utah coal mine where six miners were trapped by an Aug. 6 collapse.

Seismic waves from the event at about 6:39 p.m. MDT Thursday indicate downward motion, consistent with further settling and collapse within the mountain where the Crandall Canyon mine is located.

The University of Utah Seismograph Stations recorded the original mine collapse as a magnitude-3.9 earthquake at 2:48 a.m. MDT Aug. 6. The downward motion of waves from that event - like subsequent "after events," including the one Thursday evening - are indicative of collapse, not of motion generated by natural or "tectonic" earthquakes.

Seismologists at the University of Utah, the U.S. Geological Survey and the University of California, Berkeley, have pointed to increasingly strong evidence that the magnitude-3.9 seismic event on Aug. 6 was the mine collapse itself, not a natural earthquake.

Thursday night's bump was very shallow. Initial seismograph recordings indicated it was less than one-tenth of a mile deep, but considering uncertainties in determining depths of such seismic events, indications are the seismic event happened at a depth of less than one mile. This is quite unlike natural earthquakes, which are deeper.

As of Friday morning, Aug. 17, 22 seismic "after-events" have been recorded within about 2 miles of the mine. Twelve of those were within two days of the original collapse. However, the University of Utah Seismograph Stations installed five new seismometers near the mine, so more of the small seismic waves now are being detected. Thursday night's deadly "bump" was detected both by the new seismometers and by part of the university's pre-existing seismic network.

"These events seem to be related to the ongoing settling of the rock mass following the main collapse on Aug. 6," said Relu Burlacu, network manager for the University of Utah Seismograph Stations.

Coal mining takes place in an arc-shaped area in eastern Utah. An analysis of years of seismicity in that area by Walter Arabasz, director of the University of Utah Seismograph Stations, and his colleagues indicates that less than 2 percent of all seismicity in the coal-mining region is due to natural or tectonic earthquakes, and that
98 percent of the seismicity is caused by mining activity.

Source: University of Utah

Explore further: Image: Towing the Costa Concordia

add to favorites email to friend print save as pdf

Related Stories

New view of Rainier's volcanic plumbing

Jul 17, 2014

By measuring how fast Earth conducts electricity and seismic waves, a University of Utah researcher and colleagues made a detailed picture of Mount Rainier's deep volcanic plumbing and partly molten rock ...

Mine landslide triggered quakes

Jan 06, 2014

Last year's gigantic landslide at a Utah copper mine probably was the biggest nonvolcanic slide in North America's modern history, and included two rock avalanches that happened 90 minutes apart and surprisingly ...

Mine disaster: Hundreds of aftershocks

Apr 19, 2013

A new University of Utah study has identified hundreds of previously unrecognized small aftershocks that happened after Utah's deadly Crandall Canyon mine collapse in 2007. The aftershocks suggest the collapse ...

Recommended for you

NASA sees Genevieve squeezed between 3 tropical systems

14 hours ago

The resurrected Tropical Depression Genevieve appears squeezed between three other developing areas of low pressure. Satellite data from NOAA and NASA continue to show a lot of tropical activity in the Eastern ...

User comments : 0