2 quakes in 2 days: Is this normal?

DENVER - If you think earthquakes don't happen in Colorado, you're not alone.

"We have a little publication we title 'We don't have earthquakes in Colorado, do we?'" Dr. Vince Matthews, director of Colorado Geological Survey said.

Matthews says it's a common misconception that earthquakes don't happen in our state, but he says Colorado actually has more than 500 quakes on record including a 6.6 magnitude in 1882 that did substantial damage all along the Front Range.

"If we had a reoccurrence of that earthquake today it would do about $2.7 billion in damage," Matthews said.

Matthews points to a map of Colorado with purple dots indicating past earthquakes. Most happened in the mountains, but there have been occurrences of quakes along the eastern plains.

However, it's still hard for geologist to explain why two quakes happened in two days, hundreds of miles apart.

"It's probably coincidence that these two happened one day after another, but we really don't know enough about earthquakes that perhaps there is something that is causing them to be linked, we just don't know," he said.

Geologists say the quake in Craig that measured a 3.7 Monday night, and the one in Eads that measured a 3.9 on Sunday, occurred naturally, unlike several earthquakes that rocked the Denver metro area in the 1960s.

"We had the earthquakes in the 1960s associated with the Rocky Mountain Arsenal. They were pumping fluid down there and that triggered a large number of earthquakes and 12 of those caused damage in the metro area," Matthews said.

The last swarm of earthquakes to hit Colorado came in 2001 just west of Trinidad. The quakes went on for two days and caused structural damage to home and buildings.

Geologists say it's extremely difficult to predict earthquakes, even in regions like California where money and manpower are more readily available.

"I use the San Andres Fault as an example. It's the best studied, the best instrumented, best understood anywhere in the world by far, and we still can't predict when earthquakes are going to happen on that fault," Matthews said.

As history has shown there are some regions more prone to earthquakes.

"Statistically I think if we have a large earthquake it's probably going to be in the central part of the state where the mountains are and where the basins are," Matthews said. "There are a lot of young faults along the margins of those mountains that have moved often in the geological past."

Matthews says two earthquakes in two days are not cause for alarm, but it is helpful in dispelling the myth earthquakes don't happen here.

Geologist have no idea when the next earthquake may hit, but Matthews says you can protect yourself but removing large objects that hang above your bed, which could fall in the event of an earthquake.

If you're interested in learning more about earthquakes in Colorado, the Colorado Geological Survey has free publications and maps available at 1313 Sherman Street, Denver, CO, office 715. The phone number is 303-866-2611.