A 5.6 magnitude, likely man-made earthquake rocked north-central Oklahoma on Saturday morning, matching the strength of the most powerful earthquake to be recorded in the state back in 2011. No injuries have been reported so far, but the quake was felt in several surrounding states, according to the Associated Press, and as seen above, at least one building was damaged in the town of Pawnee, which was about nine miles southeast of the quake’s epicenter.
A barn reportedly caught fire near the epicenter as well:
The likely culprit for the minute-long quake, as with previous recent quakes in the state, was the injection of wastewater into disposal wells deep in the ground as part of state’s oil and natural-gas production, and CNN adds that Oklahoma officials are now reviewing such disposal wells near where the earthquake struck. A U.S. Geological Service report released in March warned that Oklahomans faced a 5 to 12 percent chance of experiencing a damaging “induced” quake this year:
Induced earthquakes are triggered by human activities, with wastewater disposal being the primary cause for recent events in many areas of the [central and eastern U.S.] Wastewater from oil and gas production operations can be disposed of by injecting it into deep underground wells, below aquifers that provide drinking water.
Oklahoma topped the USGS’s list of six states at risk for potential hazard from induced seismicity, and noted the increasing frequency of such events:
The central U.S. has undergone the most dramatic increase in seismicity over the past six years. From 1973 to 2008, there was an average of 24 earthquakes of magnitude 3.0 and larger per year. From 2009 to 2015, the rate steadily increased, averaging 318 per year and peaking in 2015 with 1,010 earthquakes. Through mid-March in 2016, there have been 226 earthquakes of magnitude 3.0 and larger in the central U.S. region. To date, the largest earthquake located near several active injection wells was a magnitude 5.6 in 2011 near Prague, Oklahoma.
In other words, when it comes to the frequency of earthquakes, Oklahoma is now worse than California, which sits on an active, natural fault line. To make matters worse, the USGS says that the induced quakes can unsettle the earth in such a way that natural earthquakes are later triggered independently. For a deeper look at the issue, as well as the political, regulatory, and cultural complexities surrounding the oil and gas industry in Oklahoma, check out Rivka Galchen’s informative New Yorker piece on the subject from last year. One key section:
Although disposal wells have been used for decades, the new dewatering process has led to a dramatic increase in how much water is being disposed of. (In the state, the water used in the initial stage of fracking accounts for less than ten per cent of the water pumped down disposal wells.) In Oklahoma today, an average of about ten barrels of water comes up for every barrel of oil. [Austin Holland, the head seismologist of the Oklahoma Geological Survey,] said, “We’re talking about billions of barrels, and it has to go somewhere.” Todd Halihan, a professor of geology at Oklahoma State University, in Stillwater, told me, “We’re injecting the equivalent of two Lake Hefners”—Oklahoma City’s four-square-mile reservoir—“into the ground each year, and we don’t really understand where that water is going.”