“But the second one is a little more complicated. Though fracking does cause tiny tremors, the USGS scientists found no links between the process of fracking itself and the larger earthquakes that have been occurring more frequently. They did, however, notice that earthquakes have clustered around wastewater wells in Oklahoma, Arkansas, and neighboring states. Disposing of wastewater by pumping it deep into the ground is standard practice in many industries, including mining, chemical manufacturing, and oil and gas extraction, and the oil and gas industry alone operates tens of thousands of wastewater disposal wells. But the recent surge of fracking activity, which uses millions of gallons of water to crack rock deep in the ground and release natural gas, has boosted the volume of wastewater being injected into the ground.
Stresses are everywhere in the earth’s crust, Ellsworth explains, and drilling activity can affect them. Many wastewater wells actually go deeper than gas drilling wells, reaching an older layer of rock known as basement rock, where stresses and faults are more common. The high pressure used to pump water into waste wells can cause those faults to shift, and the water itself can lubricate already-stressed faults, easing their movement and making an earthquake-causing slip more likely.”
Read more: Mother Jones