Earthquake may have been triggered by brine injection at Paradox Valley Salinity Control Facility
A magnitude 4.5 earthquake on Monday, March 4 shook San Juan County and shook up a number of residents.
The earthquake was recorded at 10:22 a.m. on Monday. The epicenter of the quake is two miles south of Bedrock, CO, near the US Bureau of Reclamation’s Paradox Valley Salinity Control Facility. The site is approximately 15 miles east of La Sal.
The initial reports listed the quake as 5.3 on the Richter scale, but the estimates were decreased to 4.5 within an hour.
Seismologists, including officials from the Bureau of Reclamation and US Geological Survey (USGS), suggest the earthquake may have been triggered by the Salinity Control Facility, which is less than one mile from the epicenter of the earthquake.
The facility injects highly pressurized, concentrated salt water (brine) into a 16,000-foot-deep well.
The officials do not suggest that the earthquake was triggered by oil and gas exploration or recovery in the area. Hydraulic fracturing (fracking) does not take place in the area and uses a completely different process than at the salinity control facility.
The earthquake was felt across San Juan County and the Colorado Plateau, with reports from Price to Grand Junction, CO and from Shiprock, NM to Chinle, AZ.
A large number of local residents reported a brief but clearly-felt quake. They report the shaking lasted for several seconds.
There have been several small aftershocks. There were no reports of injuries or damage.
The well at the Paradox Valley Salinity Control Facility was not operating at the time of the earthquake due to routine maintenance. Operations will not resume until Reclamation completes a thorough assessment of the situation.
According to the USGS, high-pressure brine injection has been known to trigger small earthquakes in the past. This earthquake is within the range of previously induced earthquakes.
The US Bureau of Reclamation monitors the location, magnitude and frequency around the Paradox Valley Salinity Control Facility.
According to the USGS, the Paradox Valley facility substantially benefits downstream water quality in the Colorado River Basin, and helps the United States meet treaty obligations with Mexico for allowable salinity levels in the river.
Historically, the Dolores River picked up an estimated 205,000 tons of salt annually as it passed through the Paradox Valley. Since the mid-1990s, much of this salt has been collected in shallow wells along the Dolores River.
The salt is then injected into deep subsurface geologic formations. The deep well program removes about 95,000 tons of salt annually from the Dolores and Colorado rivers.
The Bedrock area has been the location of numerous small earthquakes since 1962. The same area experienced a 4.4 magnitude earthquake in 2000.