A study published by the University of Utah found that the landslide at Kennecott Copper’s Bingham Canyon Mine near Salt Lake City, UT was so large that it triggered a series of earthquakes. It is the first time that a landslide is known to have caused an earthquake.
The study, published on the cover of the Geological Society of America’s magazine, GSA Today, said 16 small earthquakes were set off by the earth movement, which was mobilized by two rock slides 90 minutes apart.
"We don’t know of any case until now where landslides have been shown to trigger earthquakes," said Jeff Moore, an assistant professor of geology and geophysics at the University of Utah. "It’s quite commonly the reverse."
Moore teamed with author Kris Pankow, associate director of the university’s seismograph stations, who noted that numerous ground-movement sensors around the mine provided scientists with an immense amount of data about the April 10 landslide.
"This is really a geotechnical monitoring success story," Pankow said.
Some of the key numbers:
• The slides at 9:30 p.m. and 11:05 p.m. had magnitudes of 5.1 and 4.9, respectively, on various seismic scales. Each lasted about 90 seconds.
• Right after the second rock slide, a real earthquake of magnitude 2.5 on the Richter scale was measured. A half dozen small quakes occurred between the two slides, the other 10 after the two, but none was detected in the 10 days before the event.
• About 2.3 billion cubic feet of dirt moved in the slides. If Central Park in New York City were covered by that amount of dirt, Pankow and Moore calculated, it would be 66 feet underground.
• The landslide traveled almost 2 miles — "much longer than we would see for smaller rockfalls and rock slides," Moore said, adding "We can safely say the material was probably traveling at least 100 mph as it fell down the steepest part of the slope." Its average speed: 70 mph.