Colorado earthquake activity 1962-2006

Colorado Geological Survey Map of earthquake activity in Colorado. (Photo by Matt Morgan, Colorado Geological Survey)

The Bailey area was hit by a 2.4 magnitude earthquake Saturday, Oct. 1, at 4:20 a.m. The epicenter of the quake was off County Road 43A, near Park County Road 1034.

According to the United States Geological Survey the quake was 5 kilometers (3.1 miles) in depth. There were no injuries or damage reported.

The Colorado Geological Survey said they received reports from 29 people that they felt the earthquake.

“There are no known young faults in the area, so it appears to be a random event,” Matt Morgan, Assistant Director and Senior Research Geologist at CGS said.

“Most of the quakes in Colorado that are natural, are pretty small and not related to mapped faults that break the surface. We cannot really say that we are expecting more events.

“I can tell you, the Colorado Geological Survey is installing more seismometers in our state which will undoubtedly help us locate events with more accuracy. In fact this was the first event recorded by our newly-installed instrument near Greeley, Colo.”

In the past 40 years the CGS has only recorded three other earthquakes in the general Bailey area. They were Nov. 2, 1981, a 2.8 magnitude quake Dec. 9, 1981, no magnitude was recorded and finally, Sept. 21, 1986, a 2.5 magnitude quake was recorded.

Colorado’s largest earthquake ever recorded was Nov. 7, 1882, tipping in at a 6.6 magnitude quake centered in North Central Colorado. The largest earthquakes recorded in the Denver metro area were actually man-made earthquakes.

In the early 1960s, the U.S. Army decided to drill a huge well at the Rocky Mountain Arsenal to dispose of toxic waste fluids from operations at RMA.

Over the next several years, the north Denver Metro area experienced several earthquakes because of the disposal.

The quakes ranged from 5.0 magnitude to a 5.5 magnitude over a seven year period. These quakes caused over $1 million in damage in the immediate area.

Since the fluid injection has stopped, the Denver metro area has experienced 15 earthquakes with an average magnitude of 2.5.

“We are also conducting investigations of known young faults in Colorado to get a better handle on what the seismic risk in our state is.” Morgan said.

“We really do not have a lot of paleoseismic data on many of the faults in our state; these types of investigations where we put a trench across a young fault, help provide data such as the number of fault ruptures and their rates of recurrence.”

Overall the threat of a major earthquake in Colorado is fairly small and with the added equipment the CGS is installing in the state, we will be more aware of any shake, rattle and rolling that happens across the state.

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