UPDATE: A second earthquake occurred early Thursday registering 2.6. The epicenter was 2.5 miles northwest of Rangely at a depth of 2.7 miles.
RANGELY I An earthquake in Rangely Saturday registered 3.7 on the Richter scale. According to the United States Geological Survey (USGS) the epicenter of the light quake was 2.5 miles northwest of Rangely at a depth of just under 4 miles. No damages or injuries were reported.
It’s the second earthquake reported in northwest Colorado in a week. Thursday, April 20 a magnitude 3.9 quake was recorded 35 km northwest of Craig. The Craig quake is the largest quake in Colorado so far this year.
Two years ago in April the Rangely area experienced a series of three minor earthquakes of 1.9, 2.3 and 2.8 magnitude.
In 1967 USGS scientists learned that “swarms” of small quakes were occurring near Rangely, originating in vicinity of the oil field.
According to an “Earthquake Information Bulletin” available at the Colorado Geological Survey website, the practice of water flooding—pumping millions of gallons of water into the strata 6,000 ft. below the field to improve oil recovery—was the suggested cause.
Chevron Oil Company cooperated with the USGS over the next few years to determine what pressure levels in the injection wells triggered the small quakes and were able to bring the pressure down by removing the water and stop the earthquake swarms. According to the bulletin, “…the potential benefits to Californians and to the rest of the nation are so great that such studies as the Rangely experiment to provide a greater understanding of earthquake mechanisms will continue for some years to come.”
The full bulletin is available at bit.ly/2pZfRnI