OREANDA-NEWS. November 17, 2016. Oklahoma may end the year with as many as 600 earthquakes, about a third fewer than last year, but the magnitude of the tremors continues to grow.

The state has so far had 582 quakes of magnitude 3.0 and higher, compared with a little over 900 last year and 580 in 2014, said Michael Teague, secretary for energy and environment said at an industry event in Houston today. But on 6 November, a 5.0 magnitude quake hit near Cushing, which is also home to a massive oil storage hub, followed by many aftershocks.

A number of studies have linked the quakes to wastewater injection wells where companies dispose of water and fluids that are generated from drilling and completion work. Oklahoma has been closing or limiting operations at hundreds of wells in the past year following earthquakes. Soon after the Cushing quake this month, state regulators ordered oil and gas operators within 6 miles (10km) of the epicenter to shut wastewater disposal wells. Regulators also implemented other limits on wastewater wells within 15 miles of the quake.

"The numbers are down but the magnitude is going the wrong way," Teague said. "We are not done with this by any stretch."

State regulators have adopted a multi-pronged approach to tackle the issue, which includes steps at the policy, research and regulatory level, as well as better communication with stakeholders and communities.

In terms of research, the state is now trying to assess if the increase in magnitude is a result of water volumes or the pressure at which it is injected. It is also trying to map previously unknown fault lines.

Earthquakes have largely occurred in the Arbuckle formation in Oklahoma. As regulators determine the the exact reasons behind the quakes, the government does not plan to spread restrictions on water disposal across the state. Restrictions may get tighter and spread to include areas around the edges of the current zone if there are bigger earthquake in those adjoining areas.

"We have disposals in other parts of the state but we have no earthquakes," he said on the sidelines of the conference, so the focus remains on areas where there are earthquakes. "You can't fix a problem until you own it. We have owned this."

The state continues to study ways to dispose the water, including recycling it several times to use in future wells. This has the added benefit of limiting fresh water use. Studies also include the use of the water in the agriculture sector, for non-edible crops like cotton.

But the state does not intend to force the oil and gas industry to compulsorily recycle a certain percentage of the water from drilling operations, Teague said. It instead intends to put in place regulations that "create the space to allow businesses to operate and protect the people," he said. "The industry should figure it out themselves."