Six earthquakes hit Southern Colorado in 24 hours

TRINIDAD, Colo. (KJCT) - The City of Trinidad in Southern Colorado is the most seismically active area in the state, say seismologists.

“A swarm of six earthquakes have been detected just west of Trinidad since Thursday night,” said Cory Reppenhagen, a Meteorologist and Journalist for 9News in Denver. “Two were magnitude 4.3 including one that hit at about 1:30 Friday afternoon.”

Earthquakes are rare in most of Colorado, but Barnhart says that part of Las Animas County is the most seismically active region in the state. There have been 66 earthquakes stronger that magnitude 3.5 since 1990.

Residents in the area reported the shaking. Barnhart says the National Earthquake Information Center in Golden received about 100 individual reports of shaking. However, no damage or injuries were reported.

“It would be a quick jolt,” said Seismologist William Barnhart. “Not a strong jolt. A 4.3 is not typically something you would expect to see damage with, but it certainly might rearrange some dishes on your shelf or knock a book off your bookcase.”

Seismologists say the problem is partially caused by geology and partially by human activity.

“In this region,” says Barnhart, “There is what we’ve identified as ‘induced seismicity’ -- so effectively, human caused earthquakes.” Barnhart says wastewater injection or fracking sites from oil and gas operations can cause earthquakes. That’s when the liquid waste gets injected back into the ground.

“When you inject a fluid into the ground, that creates pressure that then kind of opens that fault,” said Barnhart. “So, it can kind of force the fault apart which makes it easier for it to slip”

But Barnhart says that there are records of earthquakes in that region even before oil and gas operations moved in. And, it is not possible to immediately attribute these new quakes to wastewater injection.

“But certainly, the higher rates of seismicity since the early 2000′s in that area is most likely a result of oil and gas activity,” explained Barnhart.