CHEYENNE—Call it the Fake Quake of 2012.

The U.S. Geological Survey announced Monday morning that their automated sensors picked up a magnitude 4.0 earthquake struck shortly after 10 a.m. about 24 miles northwest of Green River.

But that came as a surprise to the locals. Residents in Farson, the nearest town to the supposed epicenter, said they hadn't felt a thing. The Sweetwater County Sheriff's Office said exactly zero people had called local authorities to report the earth shaking.

As it turned out, the supposed earthquake was really an amplified echo of an unusually large mine blast located at the other end of the state, about 18 miles south of Gillette, said Julie Dutton, a Golden, Colo.-based USGS geophysicist. That explosion registered 3.0 on the Richter scale, Dutton said – a force equal to 32 tons of TNT.

The vibrations were picked up 400 miles away by automated seismographs at the University of Utah. As per usual policy, it was automatically registered on the USGS’ website, but the log entry was removed about an hour later after a seismographer double-checked the data.

It’s not uncommon for the USGS’ sensitive equipment to detect mine blasts in energy-rich Wyoming, she said, but in this case the blast was so strong that the seismographs miscalculated where the epicenter was.

“Probably because of the size of this one, it just screwed things up,” Dutton said.

The only question now is: who set off an explosion that big at 10:12 a.m. somewhere in rural Campbell County?


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