Following a shallow M5.8 earthquake on Saturday, September 3, 2016, Oklahoma authorities have shut down 37 wastewater wells used by the fracking industry to extract oil and gas. According to Oklahoma Governor Mary Fallin, the decision to shut down the wells was a “mandatory directive” and the total area of interest is 1 877 km² (725 mi²).

Saturday's quake hit 15 km (9.3 miles) northwest of Pawnee, north-central Oklahoma at a depth of 5.4 km (3.3 miles) and is the strongest quake ever registered in Oklahoma. Initially, it was recorded as M5.6, but the agency increased the magnitude to M5.8 on September 7.

The earthquake led the Oklahoma Corporate Commission to order 37 wells to shut down within seven to 10 days. "All of our actions have been based on the link that researchers have drawn between the Arbuckle disposal well operations and earthquakes in Oklahoma," spokesman Matt Skinner said. "We're trying to do this as quickly as possible, but we have to follow the recommendations of the seismologists, who tell us that everything going off at once can cause an [earthquake]."

Although Oklahoma is heavily dependent on energy production, which accounts for 1 in every 4 jobs in the state, the frequency of earthquakes in the state has rapidly increased beginning in 2009. From an average of less than two 3.0+ Mw quakes per year to hundreds in 2014 and 2015, leading scientists to attribute this rise to the disposal of salt water produced during oil extraction that has been injected more deeply into the ground. Numerous studies have confirmed the connection.

The USGS said Saturday that without studying the specifics of the wastewater injection and oil and gas production in this area, they cannot currently conclude whether or not this particular earthquake was caused by industrial-related, human activities. “However, we do know that many earthquakes in Oklahoma have been triggered by wastewater fluid injection,” the agency said in a statement.

In March 2016, the USGS published a report that said fracking was causing man-made earthquakes in parts of the United States, with northern Oklahoma at particular risk.

Last year, the state recorded 907 earthquakes, and in 2016 there have already been 400.

Some parts of Oklahoma now match northern California for the nation's most shake-prone.

M2.5+ earthquakes between August 5 and September 5, 2016. Credit: USGS

Since September 1, 2016, USGS recorded a total of 17 earthquakes in this region (map above and the list below).

Featured image credit: USGS