The 6.5 magnitude quake was recorded about 6 p.m. Mountain Time Tuesday evening, shaking homes from Boise to as far north as the Canadian border.
There were no reports of immediate damage, but assessments are ongoing.
The epicenter was just northwest of Stanley, the tiny town that’s the gateway to the Sawtooth Mountains.
Stanley Mayor Steve Botti drove around to check on his neighbors, but said his house absorbed the shock.
“At my house, pictures flew off the wall and stuff fell, but there was no structural damage,” Botti said. “But it was very loud. It sounded like a freight train and very severe shaking.”
Challis Mayor Mike Barrett was at city hall, about 45 miles west of the epicenter and said it was a "very sustained earthquake." So far, Barrett said there was no structural damage, but that he was still checking on individual businesses.
Another 4.8 magnitude quake just east of the town was recorded about half an hour later at 6:27 p.m.
These aftershocks can last for days – or even weeks, according to Jana Pursley, a geophysicist with the USGS in Golden, Colorado.
“You will have the aftershocks; they might slowly start dying down. You might have a stronger aftershock that will create its own little pool of smaller aftershocks,” Pursley said.
She says aftershocks can be even larger than the original quake, but that it’s rare.
Tuesday night's earthquake appears to be Idaho's second largest in state history. The 1983 Borah Peak quake, which registered a 6.9 magnitude, killed two people and caused $12.5 million in damage in Challis and Mackay.
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