Marble area shaken, but undamaged, by series of small earthquakes | PostIndependent.com

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Marble area shaken, but undamaged, by series of small earthquakes

This is from earthquaketrack.com at 4:20 p.m. MDT Tuesday, showing the several small earthquakes around the Marble and Snowmass area in recent days.

The Marble area was hit by a barrage of earthquakes — technically known as a swarm — over a 12-hour period starting late Thursday afternoon, according to the U.S. Geological Survey's National Earthquake Information Center.

The center's database shows 11 earthquakes of low magnitude between 5:41 p.m. Thursday and about 5:26 a.m. Friday. Four more were recorded Tuesday.

They ranged in magnitude from 1.1 to 2.8. Some of the quakes were powerful enough to be felt and heard by people in the Marble and Redstone areas, but they spurred curiosity rather than caused property damage or physical harm.

Redstone resident John Ostwald said he heard one of the earthquakes that first evening. "It was just a big clunk," he said.

His first thought was a box truck had run over a pothole, but he looked outside and dismissed that theory. "There were no headlights," he said.

Ostwald didn't think a lot of it until a neighbor also asked if he heard the earthquake.

Marble resident Chris Cook said he was watching a movie Thursday evening when he felt the shake. "The whole house shook, for sure," he said.

He initially wondered if there was an avalanche nearby, but he doubted there could be one close enough that he would feel it. Then he wondered if the snow slid off the roof, but there wasn't enough collected at that time.

Word of the event circulated among Marble residents and a resident confirmed via a live earthquake website that an earthquake had occurred.

While there were 11 quakes in 12 hours, eight were clustered over a 4 ½-hour period. While that might seem unusual to a layman, it wasn't necessarily raising eyebrows among scientists at the National Earthquake Information Center.

"For our state it's not unusual for that to happen," said John Bellini, a geophysicist with the center. "It's just part of the Rocky Mountains and there are small faults everywhere."

He said they were all shallow quakes, considered to be anything less than 70 kilometers below the earth's surface. There's no reason to believe that a swarm of small quakes is indicative of a larger quake to come, Bellini said.

He said a person who was sitting down in a quiet setting would likely feel an earthquake of magnitude 2.0 or higher. Only three of the eight were greater than magnitude 2.0.

When asked if water seeping underground from the heavy snowfall could have contributed to the earthquakes, Bellini said it is unlikely. There are studies examining whether spring melt can affect faults, he said.

The snowpack at the North Lost Trail outside of Marble was at 190 percent of the median for Jan. 24, according to the U.S. Natural Resources Conservation Service.

The earthquake information center's database shows the activity in Marble started before the swarm on Thursday and Friday. The activity started at 1:04 a.m. Jan. 11 with a 2.3 magnitude quake. It was followed by a 1.9 magnitude event at about 3 p.m.

They also continued after the swarm. The website earthquaketrack.com recorded a 2.4 magnitude quake at about 4 a.m. Tuesday after three other, smaller quakes.

Crystal Valley residents are familiar with occasional earthquakes. "We had a swarm of them in the mid- to late-'80s," Ostwald said.