After months of earthquakes, including the largest felt in 35 years, the state of Arkansas has ordered a temporary moratorium on the drilling of new injection wells related to natural gas-related drilling, which some locals believe are causing the seismic activity. More than 700 small earthquakes have been recorded in north-central Arkansas in the last six months.

Although the earthquake swarm might be a natural occurrence, it is also possible that it has been a consequence of the natural gas drilling technique known as “hydraulic fracturing” or “fracking.” The process entails injecting millions of gallons of chemicals, sand or fluids into a well to crack open the rocks and allow easier access to the natural gas. The problem in Arkansas appears to be related not to the drilling itself, but to the disposal of wastewater from the drilling by forcing it back into the earth into injection wells.

The Arkansas Oil and Gas Commission imposed an emergency stoppage on the drilling of new injection wells in the central part of the state after a 4.7 quake shook the area near Greenbrier on February 27.

The order only halted work at sites that started in December of last year. Those in operation before then are still in use.

The moratorium will expire in July. In the meantime, researchers will search for evidence of whether the drilling is causing the earthquakes.

The four companies operating the injection wells are SEECO Inc., Chesapeake Operating Inc., Clarita Operating LLC and Deep-Six Water Disposal Services LLC.

-David Wallechinsky, Noel Brinkerhoff