Earthquakes and Drilling -- The Short Answer

Can humans trigger earthquakes by injecting fluid into a hole in the ground?

Yes, but not just any hole. Scientists have known since at least the 1960s that injecting fluid into a geologic fault can reduce the friction between two slabs of rock, causing them to slip. The risk of causing an earthquake tends to be greater the deeper the wells and the more pressure involved. Regulators in Oklahoma began collecting data earlier this month from companies on whether they are disposing of wastewater into what is called “basement rock,” a deep layer of rock that contains many natural faults.

Does that mean hydraulic fracturing can cause earthquakes?

There are few known cases of hydraulic fracturing, or fracking, triggering an earthquake. Fracking does involve pumping millions of gallons of fluid underground at a high enough pressure to crack open dense rock. But the pumping tends to happen at shallower depths and for much shorter intervals than injecting wastewater into disposal wells. But in Ohio, researchers concluded that fracking likely triggered a series of small quakes in the state in 2014, according to a study published earlier this year.

Is there a pattern between disposal wells and earthquakes outside of Oklahoma?

Yes. The pattern exists across much of the central U.S. But some drilling hotbeds, like North Dakota’s Bakken Shale, haven’t seen a major increase in quakes for reasons that remain unclear.

Is burying wastewater from drilling and fracking the only way to dispose of it?

No. Companies have increasingly sought to recycle the chemical-laden water that flows up wells along with oil and gas, and reuse it for fracking, especially in drought-ridden areas. But injecting underground remains the cheapest method of disposal in many states and is predominant in Texas and Oklahoma.