Kennecott Utah Copper

Landslide at Bingham Canyon Mine triggered earthquakes, geologists say

By John Hollenhorst  |  Posted Jan 6th, 2014 @ 10:55pm


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BINGHAM CANYON — New studies released are stating that the landslide at Kennecott's Bingham Canyon Mine actually triggered a dozen small earthquakes.

Scientists at the University of Utah Seismograph Station said the April landslide is the first time in recorded history that a landslide has triggered an earthquake. Seismographs revealed 16 small earthquakes over a period of 10 days, as geologic faults shifted under the pit.

"It's probably — this is our hypothesis — related to rebound," said Kristine Pankow, Associate Director of U. Seismograph Stations. "And so, you move material off and it's going to come up a little bit. And it's that readjustment that has probably induced these earthquakes."

Low-frequency seismic waves captured the events. Sped up 30 times, geologists could hear the second avalanche followed by three small quakes. However, the earthquakes only occurred beneath the mine and geologists said they did not affect the Wasatch Fault.

Geologists say it's the biggest slide in modern North American history that was not triggered by a volcanic eruption.

"There have been much larger volcanic landslides, especially prehistorically, and larger landslides both volcanic and non-volcanic, outside North America," said U. spokesman Lee Siegel.

Like many other Utahns, the U. geologists were shocked by the April landslides inside Kennecott's Bingham Canyon Mine.

"It absolutely surprised me," said U. assistant professor of geology, Jeffrey Moore. "When I first saw the images, I almost thought they were fake."

Moore is one of the Utah scientists who combed through a lot of the data surrounding the landslide. The geologists are just now publishing their findings, and have discovered that only the eruption of Mount St. Helens created a bigger documented landslide.

"This will beat out all of the other large non-volcanic landslides in North American history," Moore said.

Geologists also reported that upon further research, they discovered that there were actually two landslides, 90 minutes apart. 165 million tons bedrock roared down the sides of the pit at astonishing speeds, Moore said.

"I'm estimating that this was around 100 miles per hour and that's a safe estimate, I feel," Moore said. "I feel that it could have been going faster."

If all the rock from the landslide had landed on Central Park in New York City, it would have buried it 66 feet deep. Utah's own Liberty Park could have been buried under more than 500 feet of rock measuring the size of the landslide.

On a standard Salt Lake City block, that much rock would form a tower a mile high.

"To have a landslide of this scale is absolutely surprising to me," Moore said.

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