Montana earthquake shakes Washington and Idaho

An earthquake rattled a wide swath of the Northern Rockies on Wednesday night, rousing people from Bozeman all the way to the Spokane area.

The U.S. Geological Survey confirmed the earthquake’s epicenter was located about 5 1/2 miles southeast of the Western Montana town of Lincoln, which is located northwest of Helena.

There were no immediate reports of injuries.

The USGS reported at least nine aftershocks ranging from magnitude 4.9 to 3.1.

The initial quake kept shaking for two minutes and 16 seconds, according to seismograph readings.

Residents in Lincoln briefly lost power and there was a gas leak in Helena, the National Weather Service in Great Falls said on Twitter.

Helena’s Independent Record reported that people felt the quake as far away as Idaho, Great Falls and Bozeman.

In Spokane, several people took to social media, including dozens who posted on the Spokane channel of Reddit asking if anyone had felt the earth rumbling at about midnight Wednesday.

“Definitely felt it on the South Hill, around 14th,” one user posted. “Glad I’m not going crazy!”

More took to Twitter to say they felt a small tremor in the middle of the night, while others admitted they slept through it completely. Some took the opportunity to inject some comedy into the situation.

Jon Fox, forecaster for the National Weather Service in Spokane, said his office received numerous calls, but on-duty staff late Wednesday reported not feeling the quake.

Fox said he was at home and felt the earthquake waves moving his house.

“It was like being in a boat,” he said of the ground motion.

He said the weather service received reports that birds were awakened.

In Montana, Ray Anderson, 76, told the Associated Press that it was the strongest seismic activity he had felt while living in Helena, which is about 34 miles southeast of the quake’s epicenter.

He said his wife told him the temblor – or earthquake – woke up the dogs.

Musician John Mayer, a part-time Bozeman resident, took to Twitter to marvel at the event.

“Wow,” he wrote on Twitter. “Earthquake in Montana.”

A Moscow, Idaho, resident reported broken china over Twitter.

There have been more than 70 quakes measuring larger than 4.5 in Montana and parts of Wyoming and Idaho since 1925, according to the USGS. The largest quake in state history reached magnitude 7.2 in 1959 near the city of West Yellowstone.

This quake occurred along the Lewis and Clark fault line, which runs from North Idaho to east of Helena, according to the USGS.

It is approximately 248 miles long and 50 miles wide.

The region also has a St. Mary’s-Helena Valley fault line as well as the Bald Butte fault, according to the USGS.

“More detailed field studies will be required to identify the causative fault responsible for this earthquake,” the USGS said on its web page for the quake.

Professor John Vidale at the University of Washington’s Pacific Northwest Seismic Network said the quake was likely in the strike-slip category with some vertical movement.

He said the fault zones are actually a network of fractures.

Earthquakes are generally felt more strongly near rivers and on loose soil rather than bedrock. The fact that some people in Spokane did not feel the quake is a common pattern, Vidale said.

The difference in shaking can increase by a factor of three or four times depending on location.

At a distance, the motion of a large quake is more like a rocking feeling, he said.

“The motion is going to be what we call long-period,” he said.

The largest quake in the region, in August 1959 at 7.2 magnitude, caused a landslide and killed at least 28 people at Hebgen Lake. It was well over 100 miles from the Wednesday night event.

A 1935 quake in Helena resulted in 2,525 aftershock quakes that lasted through November 1938.

The most recent earthquake in Idaho that shook Spokane was in 1983 near Challis, Idaho.

Also, an earthquake “swarm” of minor tremors occurred in Spokane, the strongest of which was measured at 4.0 on Nov. 11, 2001.

It was the largest of dozens of small quakes over several months that were felt mainly on the North Side near Corbin Park.

Similar earthquake swarms have occurred near Sandpoint, Richland and Maupin, Oregon, in more recent years.

Spokane residents may also remember the February 2001 Nisqually earthquake in Western Washington, which measured 6.8 in magnitude and was easily felt in Spokane.

The Associated Press contributed to this report.