Earthquake near southeast Utah likely human-triggered, seismologists say

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SALT LAKE CITY -- Seismologists suspect human activity triggered an earthquake in western Colorado Monday morning, which Utah residents felt throughout the southeastern, eastern and central parts of the state.

The US Geological Survey reports the 4.5 quake’s epicenter near Bedrock, Colorado shook just before 10:30 a.m.

Residents from Mexican Hat at the bottom corner of Utah, up through Moab and northeast into Price reported feeling the tremors.

Residents in western Colorado also felt the jolt, including in Durango and Grand Junction. No one reported damage from the trembling.

Chuck Schildt manages Hogan Trading Company on Main Street in Moab, and said the entire building shook. The front doors creaked open, and water in one of the fountains began to move vigorously.

He immediately got text messages about the quake.

“’It was an earthquake, it was an earthquake-- did you feel it?’” he said, recounting the messages. “I go, ‘Yeah we felt it. We're just kind of shocked.’”

Craig Hill said the quake awoke him, because his bed started to shake.

“It seemed like there was a dump truck or a grader just going down, chowing up the asphalt out here, or maybe a building falling down,” he said, describing what he felt.

Hill said he figured it was just Mother Nature.

Seismologists at the University of Utah suggest something else behind the shaking.

“In this case, it's pretty easy because we look and we say, ‘Oh-- that's Paradox Valley,” said seismologist Jim Pechmann. “There's been induced earthquakes there for many years.”

By induced, Pechmann means human-induced. He pointed to a map in the U of U Seismology Center were a number of red dots swarm Paradox Valley in western Colorado.

According to Pechmann, the government runs a saltwater injection site in that area.

“The U.S. Bureau of Reclamation has been injecting saltwater since the 1990s,” Pechmann said.

He explained that the decades-long project injects saltwater three miles into the ground, to keep it out of the Colorado River.

He indicated the increased salinity could impact farming and other water uses downstream.

Monday’s earthquake is the largest one ever recorded in that area, Pechmann said.

The U.S. Bureau of Reclamation issued this statement about the earthquake:

“The U.S. Geological Survey reported that an earthquake occurred at 10:22 a.m. MST, on Monday, March 4, 2019, near Reclamation’s Paradox Valley Salinity Control Facility near Bedrock, Colorado. Reclamation maintains a comprehensive network of seismic monitoring instruments in the area, which indicated a preliminary magnitude 4.1 for this earthquake. The quake was felt by employees at the Reclamation facility and residents in surrounding areas.
The Paradox Valley Salinity Control Facility injects highly pressurized, concentrated salt water (brine) into a 16,000-foot-deep well, preventing the brine from entering the Dolores River. The well 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.
High-pressure brine injection has been known to trigger small earthquakes in the past, and today’s event was within the range of previously induced earthquakes. Reclamation’s seismic network in the area monitors the location, magnitude and frequency around the Paradox Valley Salinity Control Facility. Reclamation will continue using that network to monitor earthquakes in the area.
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. 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 by the Paradox Valley Salinity Control Unit in shallow wells along the Dolores River and then injected into deep subsurface geologic formations. The deep well injection program removes about 95,000 tons of salt annually from the Dolores and Colorado rivers.”

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