Biggest temblor in 34 years may not be linked to massive underground volcano  

The biggest earthquake in 34 years rolled Yellowstone National Park Sunday morning, but no damage or injuries have been reported.

In fact, most people in the area either slept through it or did not even feel it. At 6:34 a.m. the magnitude 4.8 quake shook 4 miles north-northeast of Norris Geyser Basin, which is 18 miles south of Gardiner, Mont., at a depths of 4.2 miles.

“It was considered pretty light by seismic standards,” said Dan Hottle, a Yellowstone Park spokesperson at Mammoth Hot Springs. “No injuries, no damages.”

Like lots of people on Sunday morning, Hottle was sleeping in.

“Most of us slept right through it,” said Rebecca Demaree of Gardiner. “I didn’t feel a thing.”

“I wasn’t even aware that we had an earthquake on Sunday,” said Jeremy Medeiros of West Yellowstone.

“It woke the town up, but there were no damages,” said Barbara Shesky, executive director of the Gardiner Chamber of Commerce.

The big caldera beneath at least one-fourth of Yellowstone isn’t to blame, or at least is not the prime seismic suspect.

“This one seems to be more tectonic in nature,” said Jamie Farrell, seismologist with the University of Utah in a reference to the plates that make up the earth’s crust.

He said it appears to have been a slip on a fault, with subterranean rock sliding against other rock north of the caldera. But the caldera could have added stress to facilitate the quake, Farrell said.

According to a Geological Survey Yellowstone Caldera map, Norris is just a few miles north of the volcanic crater.

The likelihood of the caldera erupting in the future is slim, he said. In fact, Farrell said he is not even 100 percent convinced it will ever occur.

“The least likely but worst-case volcanic eruption at Yellowstone would be another explosive caldera-forming eruption such as those that occurred 2.1 million, 1.3 million and 640,000 years ago,” according to the U.S. Geological Survey.

However, the probability of such an eruption in any given century or millennium is exceedingly low. The last time the caldera blew in Yellowstone was just a blink of the eye in geological time, but Earth has been around more than 3.5 billion years, making geological time just shy of infinite.

Farrell and his colleague will continue to monitor the data from Sunday’s quake and continue to monitor Yellowstone’s seismic activity.

The 4.8 quake was the largest of four that rocked the park Sunday, which is not unusual. Yellowstone has 1,500 to 2,000 earthquakes annually, Farrell said.

A quake at 4:36 a.m., a magnitude 3 quake got the seismic ball rolling 17 miles south of Gardiner. At 1:14 p.m. a magnitude 3 quake hit 16 miles south of Gardiner and at 5:59 p.m., and another tremor shook the ground 17 miles south of Gardiner with a magnitude 3.5, according to the University of Utah Seismograph Stations.

Despite all the temblors, people who live north and west of the epicenter barely detected the quake. Sunday’s shakeup was part of a series of at least 25 quakes kicking off since Thursday.

“The magnitude 4.8 main shock was reportedly felt in Yellowstone National Park and in the towns of West Yellowstone and Gardiner, Mont.,” said Utah Seismograph Stations.

A magnitude 4 is considerably bigger than a magnitude 3, Farrell said.

Sunday’s quake was the largest in Yellowstone since Feb. 2 1980, when a magnitude 4.8 quake struck. The August 1959 Hebgen Lake quake just outside Yellowstone, was a 7.3 magnitude, Farrell said.

The Geological Survey would like to record people’s feelings about earthquakes they experienced. Go to the U.S. Geological Survey’s webpage, “Did You Feel It?” at http://earthquake.usgs.gov/earthquakes/dyfi/ and tell your recent earthquake story.