A little over eight months into the year, Oklahoma has broken a new yearly record for earthquakes.
The state recorded its 587th earthquake of 3.0 magnitude or higher early this week, breaking the previous record of 585. That record was set for all of 2014, meaning that Oklahoma has now had more 3.0 magnitude or higher earthquakes so far in 2015 than it did in all of 2014. So far this year, E&E; News reports, Oklahoma’s averaged 2.5 quakes each day, a rate that, if it continues, means the state could see more than 912 earthquakes by the end of this year.
Oklahoma has also experienced 21 4.0 magnitude or greater earthquakes so far this year — an increase over last year, which saw 14.
Last year, Oklahoma was the most seismically active state in the lower 48 U.S. states. Its 585 quakes were a major spike from the year before, which saw around 100 earthquakes. In 2014, the state had already surpassed its 2013 record by April.
Oil and gas activity is seen as a suspect for this surge in earthquake activity, both in Oklahoma and in other oil- and gas-heavy states that have experienced swarms of earthquakes. From 1991 to 2008, Oklahoma experienced no more than three 3.0 or higher earthquakes a year. Then, in 2009, earthquake activity started to increase in the state — and judging by the records broken in 2014 and 2015, it hasn’t stopped. That increase in earthquakes since 2009 has been tied to hydraulic fracturing operations in the state — specifically, the injection of fracking wastewater into deep, underground wells. If those wells are close enough to fault lines, the activity can trigger the line to slip, which can cause an earthquake.
“As long as you keep injecting wastewater along that fault zone, according to my calculations, you’re going to continue to have earthquakes,” Arthur F. McGarr, chief of the induced seismicity project at the federal Earthquake Science Center in California, told the New York Times in April.
The injection of fracking wastewater has been confirmed as a possible earthquake trigger by the U.S. Geological Survey, and according to the agency, earthquakes linked to fracking are on the rise in the U.S.
“These earthquakes are occurring at a higher rate than ever before and pose a much greater risk to people living nearby,” Mark Petersen, the USGS National Seismic Hazard Modeling Project chief, said in a statement in April. “The USGS is developing methods that overcome the challenges in assessing seismic hazards in these regions in order to support decisions that help keep communities safe from ground shaking.”
Other states, including Texas and Ohio, have also linked earthquakes to wastewater injection. The process of fracking itself — rather than the injection of wastewater — has also been singled out as a possible earthquake inducer: scientists linked a series of earthquakes in Ohio to fracking in January.