Human activity eyed as cause of Bedrock earthquake

An illustration showing the effects that fluid injection and withdrawal can have on nearby tectonic faults.
Illustration courtesy of the U.S. Geological Survey

Human activity has induced earthquakes in the past, and Monday’s earthquake may be another such example, according to the U.S. Bureau of Reclamation. The bureau said in a statement Monday, March 4, that the earthquake in the area March 4 “was within the range of previously induced earthquakes” at a nearby water treatment facility.

Studies of a 4.4 magnitude tremor from 2000 that occurred nearby “make a strong case” that the previous quake was induced by the water treatment operations, which use high pressure to inject saline deep underground.

“Similar studies will be necessary to determine if, or how, the March 4, 2019, might have been induced by injection,” the U.S. Geological Survey. said.

After decades of a steady earthquake rate (average of 21 events per year), activity increased starting in 2001 and peaked in 2011. Human-induced earthquakes are suspected to be partially responsible for the increase.
Photo courtesy of the U.S. Geological Survey

The Paradox Valley Salinity Control Facility removes about 95,000 tons of salt annually from the Dolores and Colorado rivers, re-depositing the saline into a three-mile-deep well once it’s removed. Deep-Earth injection operations such as this are known to cause mild earthquakes, according to USGS.

“While most induced earthquakes are small and present little hazard, larger and potentially damaging manmade earthquakes have occurred in the past,” the USGS said on its website.

The well at the Paradox Valley facility was not operating at the time of the earthquake due to routine maintenance, and operations will not resume until the bureau completes a thorough assessment of the situation, according to the bureau’s statement.

“The Paradox Valley Salinity Control 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,” the bureau said.