Residents of Silt and New Castle may have felt their homes shake early Monday afternoon as a 3.3 magnitude earthquake hit 5 kilometers south of New Castle.
The earthquake, the largest to strike Garfield County in the past 10 years, was 5 kilometers in depth and was the Silt-New Castle area’s third recorded earthquake since October.

It came a week after it was reported that a series of earthquakes, known as a swarm, hit the Marble area resulting in 11 earthquakes ranging from magnitude 1.1 to 2.8.

“It felt like a 300-pound person was running across my living room,” said Silt resident Bob Koper.

He was asleep in front of the television when he was awakened as his whole house began to shake.

According to the U.S. Geological Survey, seven people reported the earthquake Monday.

After the 2.9 magnitude quake on Christmas Day at New Castle, citizen activist groups asked Colorado oil and gas regulators to analyze the recent earthquakes near New Castle to determine whether nearby injection wells were a cause. A 2.2 magnitude quake was recorded near New Castle in October.

High-volume injection wells used to dispose of water from fracking have been linked to dramatic increases in earthquakes in Oklahoma in recent years, though injection wells in Garfield County are not of the volume found to cause seismic activity.

“It’s probable that it’s not induced by injection wells, but we want to make sure,” said Leslie Robinson, chair of the Grand Valley Citizens Alliance, which with the Battlement Concerned Citizens made the request of the Colorado Oil and Gas Conservation Commission.

Julie Dutton, geophysicist with the National Earthquake Information Center, said Monday she doubts any connection.
“There are so few earthquakes there, it is difficult to make any kind of correlation,” she said. “It’s not something that we think is becoming more active. The area will and does have infrequent earthquakes.”

James Hagadorn, a scientist with the Denver Museum of Nature and Science who writes a monthly column that appears in the Post Independent, added that in the western United States, the three main causes for earthquakes are volcanoes, faults and people — injection wells.

“That happens all the time in Colorado,” he said. “People did not believe that humans could cause earthquakes until a geologist in Golden figured it out. Colorado was the first place to discover that people can cause earthquakes.”

In his mind it is always a good idea to ask questions about increasing seismic activity even if it turns out to just be nature at work.

“The Earth is a dynamic place, and sometimes it lets us know it’s alive,” he said. “A geologist might ask if there is a major fault or injection well nearby. If you can eliminate two of the three: fault, volcanoes and people, then there’s only one thing it can be.”

He noted that most earthquakes induced by human activity are very small.

At 3.3 on the Richter Scale, the earthquake is considered minor. Quakes of that magnitude can be felt felt by some people, but are not likely to cause damage.

An estimated 30,000 earthquakes occur each year worldwide with a magnitude of 2.5 to 5.4.