 More than 230 earthquakes with a magnitude greater than 3.0 have shaken the state of Oklahoma already this year. Researchers say there has been a forty-fold increase in the rate of quakes in the US state between 2008-13. “It really is unprecedented to have this many earthquakes over a broad region like this,” says study co-author Geoffrey Abers of Cornell University. They then modeled the flow of the water and calculated the physical properties of the rocks into which the water was injected. Sudden swarm 
 
 There has been increasing evidence of links between the process of oil and gas extraction and earthquakes in states like Arkansas, Texas, Ohio and Oklahoma in recent years. He says several earthquakes in Texas over the past few years have been linked to wastewater injection but the scale of these events pales in comparison with what is happening in Oklahoma.
– Earthquakes in Oklahoma are up more than a hundredfold in recent years, and a new study spies a pretty clear link between the shaking and the fracking that has given the state's economy a huge boost. Researchers took a close look at four specific sites where wastewater from oil and gas extraction was injected into the ground and found that the process could be linked to swarms of quakes in areas up to 20 miles away from the sites, reports the BBC. The four wells examined have been pumping four million barrels of water a month to a depth of around two miles underground. At one site linked to the wells, a small town called Jones, there have been more 2,500 earthquakes greater than magnitude 3.0 since 2008—a fifth of the total in the central and western US during that period. "It really is unprecedented to have this many earthquakes over a broad region like this," a study co-author tells Scientific American, explaining that wastewater injection can cause quakes by sending out waves of fluid pressure, causing faults miles away to slip. "Most big sequences of earthquakes that we see are either a main shock and a lot of aftershocks or it might be right at the middle of a volcano in a volcanic system or geothermal system. So you might see little swarms but nothing really this distributed and this persistent," he says. (In Texas, several small towns troubled by quakes are considering banning fracking.)