Second earthquake in two days rattles Colorado

August 18, 6:59 AMDenver Weather ExaminerTony Hake

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A 3.7 magnitude earthquake shook northwestern Colorado, the
second quake to hit the state in two days.

Following on an earthquake in the southeastern corner of the state on Sunday, a second temblor shook northwestern Colorado on Monday night. Occurring at 8:50pm, the magnitude 3.7 quake was centered 11 miles north of Craig.

According to the U.S. Geological Survey (see details below), the quake’s origin was 3.1 miles below the surface. No damage was reported as the quake was felt in nearby Craig and surrounding communities and as far north as Rawlins, Wyoming.

The quake Monday was the second in two days. Sunday evening a quake centered 26 miles north of Lamar measured as a 3.9 magnitude temblor and was felt into western Kansas. Click here for that story.

There are approximately 100 potentially active faults in Colorado and more than 400 temblors of magnitude 2.5 have occurred in the state since 1870. The Sangre de Cristo Fault in the mountain range of the same name and the Sawatch Fault along the Sawatch Range are considered to be the potentially most active.

The state’s largest quake occurred on November 7, 1882 along the northern Front Range and measured 6.5 on the Richter Scale.  In writing about that quake, the Longmont Ledger of November 10, 1882, said, "It is claimed by the oldest settlers in Denver that this is the first known instance of an earthquake having visited Colorado."

According to the Colorado Division of Emergency Management, the costliest quake was a 5.3 magnitude temblor that occurred on August 9, 1967 and was centered near Commerce City. The quake caused more than $1 million worth of damage and is thought to have been caused by the injection of liquid waste into the earth at the Rocky Mountain Arsenal.

Earthquake Details

Related:  Colorado earthquake history (USGS)