Earthquake Swarm Continues To Shake Central Idaho

Apr 14, 2014

This intensity map from USGS shows where Monday afternoon's earthquake was felt.
Credit U.S. Geological Survey

The U.S. Geological Survey reports a 4.6-magnitude earthquake occurred Monday afternoon 14.2 miles north of Challis. Early Monday morning, a magnitude 3.0 earthquake was measured 11 miles north northwest of the town.

Mike Stickney is the director of the Earthquake Studies Office at the Montana Bureau of Mines and Geology. He says this swarm of earthquakes in central Idaho started on March 24. He says at least 12 have been greater than magnitude 3, and many smaller tremors have also been measured.

On April 10, a magnitude 4.1 quake was measured. On Saturday, a magnitude 4.9 earthquake shook the same remote area.

Stickney says swarms like this one can last for a few days up to several months, and there is no way of knowing how long the event will last. “This is certainly the most vigorous swarm in recent memory,” says Stickney, “[but] this isn’t something that’s unprecedented.”

A USGS intensity map shows light shaking was felt as far south the Wood River Valley, and some shaking was felt north and east into Montana.

“We really do not know if something bigger is coming,” says Stickney. “We certainly don’t have any reason to expect a larger earthquake to occur as part of this swarm. But at the same time we have no way of knowing that for certain.”

The largest earthquake ever recorded in Idaho was on October 28, 1983 when a 6.9 magnitude quake shook Borah Peak.

“The safest thing to do would be to assume that there could be another earthquake,” says Stickney. “I’d be surprised if there was a larger earthquake, but we really can’t rule out that possibility. Unlike the weather, we can’t predict earthquakes or see them coming.”

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