Third earthquake in four days hits Colorado

August 19, 10:41 AMDenver Weather ExaminerTony Hake

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The third earthquake in four days struck Colorado early Wednesday
morning in the same location a previous one happened on
Monday.  (Map: USGS)

Colorado experienced its third earthquake since Sunday as a small 2.7 magnitude quake occurred early Wednesday morning. According to the U.S. Geological Survey, the latest quake occurred in the same area as the temblor Monday night with the epicenter 11 miles north of Craig.

The latest quake was recorded at 1:58am and was centered 3.1 miles below the surface, much like the previous one in the Craig area. While the temblor was small enough that it most likely wasn’t felt, the recent quakes have garnered the attention of seismologists and geologists in the state.

Earthquakes in Colorado are not unusual as the USGS says nine were recorded this year and more than 100 in the last four years. However having this many in such a short time span is not particularly common. The last time the state experienced two quakes of magnitude 3.5 or greater so frequently was in 2001 when an earthquake “swarm” shook the area near Trinidad. During that event, from August 28 and September 21 of that year, 12 earthquakes of magnitude 2.8 to 4.6 struck just west of the southern Colorado city.

More knowledge about Colorado's seismological and geological features needed

The Colorado Geological Survey said that the events highlight just how little is known about Colorado’s geology and its potential for earthquakes. Vince Matthews, Director of the Colorado Geological Survey told Examiner.com that in the case of the Craig quakes, while there are some young faults in the area there haven’t been extensive studies on the area. Matthews said, “We simply don’t know as much as we should about what is going on under the surface in Colorado.”

Wednesday morning Matthews submitted a request to the USGS that they deploy portable seismometers to the Craig area. The sensors would allow geologists and seismologists to more closely monitor the situation and potentially gather new information on what lies below the area. He said that there were a great number of young, “fairly substantial” faults in the state that warrant more study.

Map of historical earthquakes in Colorado from 1867 - 1996.
(Map: Colorado Geological Survey)

Three faults in the state capable of producing a magnitude 7.0 or greater earthquake

Matthews said that in his opinion the earthquake on Sunday near Eads held the greater interest of the two quake locations. He said he believes it may have occurred along a previously unmapped part of the Cheraw Fault, one of three the USGS has identified in Colorado as having the potential to generate a magnitude 7.0 quake or bigger. The fault runs 28 miles from roughly Cheraw to Haswell in the southeastern corner of the state.

The other two significant faults are the Northern Sangre de Christo Fault and the Southern Sawatch Fault, both located in the mountain ranges from which they draw their names. The Sangre de Christo Fault runs more than 110 miles in length from the New Mexico border north while the Sawatch Fault is nearly 30 miles long from Leadville south to the South Arkansas River.

Experts point out that there are nearly 100 potentially active faults throughout the state. Since 1870, more than 500 temblors of magnitude 2.5 have been recorded.

Colorado Fault Map (USGS)