Used to be, each area of the nation had its own distinctive pluses and minuses. If you lived in Florida, you enjoyed the sweet beaches, but you endured hurricanes every so often. If you lived in Chicago, you had to weather bitter winters. If you lived in California, you endured earthquakes. If you lived in Oklahoma, you lived through yearly tornadoes and blazing hot summers.
But now, Oklahoma has another claim to infamy: earthquakes. Over the last several years, usually seismically quiet Oklahoma has become the center of small quakes, even more than California, which sits atop one of the most active fault lines in the world.
In 2014, Oklahoma has seen more earthquakes than the left coast, and a study published online this week in Science definitively links four of Oklahoma’s most prolific wastewater wells to a swarm of 2,547 small earthquakes near Jones. From the paper:
Unconventional oil and gas production provides a rapidly growing energy source; however, high-production states in the United States, such as Oklahoma, face sharply rising numbers of earthquakes. Subsurface pressure data required to unequivocally link earthquakes to injection are rarely accessible. Here we use seismicity and hydrogeological models to show that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm. Earthquake hypocenters occur within disposal formations and upper-basement, between 2-5 km depth. The modeled fluid pressure perturbation propagates throughout the same depth range and tracks earthquakes to distances of 35 km, with a triggering threshold of ~0.07 MPa. Although thousands of disposal wells operate aseismically, four of the highest-rate wells are capable of inducing 20% of 2008-2013 central US seismicity.
The water injection wells can create pressure that acts to reduce forces acting to keep faults locked, and therefore trigger earthquakes, the study states.
Current practice does not always require disclosure or monitoring of the controversial practice.