The onset of Oklahoma’s earthquakes several years ago suddenly changed life in the north-central part of the state. But since they are self-inflicted, this seismic shift need not be a permanent one.

The earthquakes have been triggered by the injection of large volumes of wastewater in deep disposal wells, which is able to raise fluid pressure and loosen long-locked faults in the crystalline “basement” rock below. The wastewater comes from oil and gas wells in the area, which cough up a lot of dirty, salty water along with the hydrocarbons.

Just a few weeks ago, a magnitude 5.0 earthquake caused a fair amount of damage to buildings in Cushing—buildings that were never designed to withstand seismic activity. And in September, a magnitude 5.8 quake in Pawnee set a historical record for the state.

A new study from Stanford’s Cornelius Langenbruch and Mark Zoback, however, concludes that things should get better soon in the Sooner State. That’s because the Oklahoma Corporation Commission ordered injections to be reduced earlier this year, which should start to pay off in the near future.

It’s hard to overstate just how quickly things changed. Injections gradually increased starting in 2002 and skyrocketed between 2012 and 2015. Before 2009, when things got weird, Oklahoma averaged about one earthquake of magnitude 3.0 or higher per year. In 2015, the state saw about 900. The amount of pent-up seismic energy released in earthquakes over the last eight years is equivalent to at least 1,900 years' worth of “natural” quakes.

Langenbruch and Zoback worked out a statistical model relating earthquake activity to the rate of wastewater injections, including the area’s underlying seismic susceptibility. They calibrated the model to the existing data over a couple of different windows of time to make sure their relationship was sound.

Because the faults responsible for the earthquakes are significantly deeper than the sedimentary rock the disposal wells inject water into, water pressure (and seismic activity) in the basement rock lags behind injection activity by several months. The rate of injections hit its peak in early 2015, before slumping oil prices slowed production.

With the model calibrated, we can now look to the future. The state’s new rules are limiting the rate of injections to 40 percent below where it was in 2014. That’s still a lot higher than the pre-2009 rate, but it’s spread out over a larger area. Given time, the water pressure far below the surface will relax.

The researchers’ model predicts that the number of earthquakes stronger than magnitude 3.0 should already be on the decline this year (though aftershocks following larger earthquakes like the recent 5.0 in Cushing can muddy that trend). Even if injections hold constant at the new rate, the situation should improve markedly. Within a few years, the risk of larger earthquakes drops off significantly, and after ten years, things should look more like they did in 2009.

But even if this model prediction is right on the money, Oklahomans will probably want to hang onto that earthquake insurance. There is one outlier that doesn’t fit the model very well: the magnitude 5.6 earthquake in Prague, Oklahoma in 2011. That occurred before the critical pressure threshold calculated by the model was crossed.

The model is working out general relationships over the entire area, but small-scale details can make a big difference. Depending on the location of fractures and other pathways for water, it could be that one of the injection wells near Prague had a direct line to a fault, resulting in a larger but localized pressure increase in just the right (or, more accurately, wrong) place. That will continue to be a possibility, even as the overall rate of earthquakes eases up, unless problematic geology can be identified.

Still, this is welcome news for Oklahomans eager to trust the ground beneath their feet again.

Open Access at Science Advances, 2016. DOI: 10.1126/sciadv.1601542 (About DOIs).