(CNN) Oklahoma is one of the more unlikely places in the United States to experience earthquakes. But in the six years that Scott Pruitt has served as the state's attorney general, Oklahoma has been rattled by hundreds of quakes with a magnitude of 3.0 and greater, with some areas facing the same level of risk as high-hazard parts of California.

Scientists from the U.S. Geological Survey, Stanford University and the Oklahoma Geological Survey link the uptick in quakes -- many of which are low-magnitude -- to a wastewater disposal process related to hydraulic fracking. That's a procedure in which a mixture of chemical-laced fluids and sands are injected into wells deep beneath the state's surface to extract oil and gas.

For the last several years, frightened residents waited in frustration as the state's regulatory arm, the Oklahoma Corporation Commission, slowly cranked into action -- and ultimately concluded the surge in earthquakes was directly related to operation of disposal wells, where the wastewater from oil and gas production is injected.

In states such as California and New York, attorneys general have been quick to step in on environmental issues. But Pruitt, who is Donald Trump's pick to lead the US Environmental Protection Agency , remained unengaged even as the earthquakes turned into a legal morass in the courts in his state.

Pruitt embodies the rightward shift about to hit Washington later this week when Trump is sworn into office. He is one of the President-elect's most controversial Cabinet picks and his combative stance toward the EPA and his seeming disinterest in the earthquakes unnerving his constituents are among the reasons why. He was questioned on the connection between fracking and earthquakes Wednesday at his Senate confirmation hearing

"I have acknowledged that I am concerned," Pruitt said in an exchange with Vermont Sen. Bernie Sanders.

"If that is the kind of EPA administrator you will be, you are not going to get my vote," Sanders responded before questioning moved on to other lawmakers.

Many Republicans at the hearing saw Pruitt, who has sued the EPA more than a half-dozen times, as the right person to lead what they view as a wasteful agency that over-regulates.

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Pruitt declined to comment on the earthquakes or his tangles with the EPA before his confirmation hearing.

But when asked about his role on the earthquakes, one of his spokesmen said the attorney general's office had "no legal authority in these matters" and referred questions to the Oklahoma Oil & Gas Association, as well as state regulators at the Oklahoma Corporation Commission, who have overseen the development of "directives" for companies on how they should address Oklahoma's increased seismicity.

"I personally know Oklahoma Attorney General Scott Pruitt, and can say that he has shared the Commission's concerns for Oklahoma's seismicity trends in recent years," Oklahoma Corporation Commissioner Todd Hiett said in a statement.

Dana Murphy, the commission's Chairman-elect, added that "industry compliance" with their directives "has thus far been outstanding."

"There has been no need to request assistance from the attorney general," Murphy said.

Aides to Pruitt noted he worked closely with the state insurance commissioner to protect consumers from premium spikes in earthquake policies. But they said Pruitt did not have any direct control over the actions of the Oklahoma Corporation Commission unless its members were to act outside the confines of their authority.

Complicating the debate, Oklahoma scientists and officials are still mapping all of the state's natural fault lines as they try to trace where the wastewater flows once it is injected underground -- so there have been disagreements both within the scientific community and among energy producers about the exact cause of each quake.

Still, Pruitt's overall silence on how he would approach a difficult issue that has wreaked havoc in his state is noteworthy because the EPA, as it notes on its website , "regulates the construction, operation, permitting, and closure of injection wells used to place fluids underground for storage or disposal" as part of its role in preventing contamination of drinking water.

Becoming more aggressive

Over the last year, Oklahoma has become more aggressive in trying to stop the quakes. The state now requires more frequent reporting of the amount of wastewater injected into wells. It limits the amount that can be injected in certain areas. And it's developed quicker procedures to shut down wells if earthquakes occur nearby.

But for a long time, many Oklahoma residents felt state officials were slow to act, and they have filed a series of class action lawsuits against oil and gas producers.

One of the first legal cases was brought against oil and gas producers by a woman who was hit by flying stone while sitting in her recliner during a 5.7 quake in Prague, Oklahoma, in 2011. A lower state court initially threw out the suit, saying they didn't have jurisdiction over the matter. But the Oklahoma Supreme Court overturned the lower court's ruling in 2016, saying homeowners could sue energy companies for damages in state trial courts, giving them a right to a jury when seeking damages.

The companies argued that the Oklahoma Corporation Commission -- not the state courts -- should handle damage claims because it oversees the regulations for oil and gas operations.

The record-setting 5.8 quake in Pawnee, Oklahoma, in September led the Pawnee Nation, which unsuccessfully tried in 2015 to impose a moratorium on fracking on their tribal lands, to sue the US Bureau of Indian Affairs and the Bureau of Land Management asking them to void drilling permits for natural oil and gas wells.

The Bureau of Indian Affairs declined to comment on the pending litigation and the Bureau of Land Management did not respond to a request for comment.

Damage at White's Foodliner grocery store following a record setting earthquake in Pawnee, Oklahoma, last September

For several years as the tremors increased in frequency, Andrew Knife Chief, executive director of the Pawnee Nation, said residents constantly came to him, asking what he could do to stop them. They were seeing mysterious fish kills in nearby rivers, and were increasingly concerned that their drinking water could become contaminated by wastewater disposal wells or contractors who hauled that wastewater away from the drilling sites.

"We went from having a hundred (earthquakes) a year, maybe even fewer than that, to a couple of thousand a year -- and there were no signs of it slowing down between 2008 and 2015," Knife Chief said. "Then the frequency started to die down a little bit, but the intensity started to ramp up, so we really felt like we were in a shooting gallery here in Pawnee."

The Pawnee quake also led another group of residents to file a lawsuit against more than two dozen energy companies, accusing them of "reckless disregard for public or private safety."

Only two of those energy companies, Eagle Road Oil LLC and Cummings Oil Co., have been named in the lawsuit so far. Neither company responded to a request for comment but Eagle Road's parent company, Jericho Oil Corp., said in a statement on its website that "Eagle Road conducts its operations in accordance with industry standard practices and adheres to state guidelines and regulations."

The wheels of government turn much more slowly than these earthquakes are occurring

"The earthquakes have emerged in Oklahoma much faster than the culture and the state infrastructure has been able to respond," said Pawnee Mayor Brad Sewell, noting that many Oklahomans don't have insurance for earthquakes and are concerned about their property values. "There's a sense that a lot of the officials are perhaps reluctant to upset the status of a major industry in this state. ...The wheels of government turn much more slowly than these earthquakes are occurring."

Sewell, a Democrat, said "Pruitt is not even on my radar as far as earthquakes are concerned, and I guess that in itself is telling. While I don't know anything he has said specifically about saltwater wells and earthquakes, I've seen his comments on other environmental issues and it doesn't bode well with respect to earthquakes," he said, referring to Pruitt's aggressive posture toward the EPA in his lawsuits and other statements.

Sewell said it's been a struggle to get Oklahomans who were affected by the September quake to come forward.

"They don't have insurance, so they feel like they are out of luck," Sewell said in an interview with CNN. "This is actually a rather poor region and many of these people don't feel like they really have the resources to do anything about the damage they've experienced."

Beyond the concerns of individual homeowners, environmentalists have continued to warn of the possibility of a catastrophic environmental disaster involving the many pipelines that crisscross Oklahoma.

November's 5.0-magnitude earthquake in Cushing, Oklahoma, renewed those fears. The town is the site of the largest storage center for commercial crude oil in North America -- tens of millions of barrels of crude oil are stored there in what is known as the "pipeline crossroads of the world."

"We have thousands of miles of pipelines running through our county," said Knife Chief, noting that the tribe is based just 25 miles from Cushing, "and we don't know where any of them are. Of course, it's a worry. It's a huge worry."

Chad Warmington, President of the Oklahoma Oil and Gas Association, told CNN in a telephone interview that state officials, as well as responsible energy companies, are now aggressively tackling the problem. He pointed to predictions that the number of earthquakes will drop in the coming years, because of the new restrictions. Among the new restrictions, the Oklahoma Corporation Commission has called on energy producers to shut down some disposal wells and reduce the volume of wastewater injected in some sensitive areas by 40%.

When asked whether Pruitt could have played a more prominent role, Warmington credited Oklahoma Republican Gov. Mary Fallin with pulling together the group in 2014 that decided what should be done about the earthquakes.

Guided by several Stanford scientists and state geologists, the working group determined that the tremors were triggered by the enormous pressure that the oil and gas wastewater injections were putting on natural faults in the ground.

"(Fallin) pulled together everybody who had a stake in what should be done about seismicity, and there wasn't a place for the attorney general, because he doesn't really have any role in the regulatory aspects of seismicity or oil and gas in Oklahoma," Warmington said.

A spokesman for Fallin didn't comment on why Pruitt was not included in that working group.

Questions about Pruitt's closeness to industry

The surge in earthquakes in his home state has highlighted questions about Pruitt's closeness to the oil and gas industry, which is certain to be one of the most contentious lines of inquiry at his confirmation hearing.

Pruitt has pledged to bring a different sensibility to the agency.

I intend to run this agency in a way that fosters both responsible protection of the environment and freedom for American businesses

"The American people are tired of seeing billions of dollars drained from our economy due to unnecessary EPA regulations, and I intend to run this agency in a way that fosters both responsible protection of the environment and freedom for American businesses," he said in a statement when he was named by Trump.

Pruitt strengthened his ties to the energy industry when he headed the Republican Attorneys General Association. Using 2011 documents obtained from open records requests, The New York Times revealed that Pruitt and other Republican attorneys general had formed a behind-the-scenes alliance with energy producers to challenge Obama administration regulations. Those companies were key contributors to his 2013 re-election campaign.

A staunch social conservative, he focused during his eight years in the Oklahoma State Senate on anti-abortion measures, religious freedom and fiscal responsibility. He ran unsuccessfully for Congress in 2001 and Lieutenant Governor in 2006, before winning an election for attorney general in 2010 and pursuing a bold agenda to challenge Obama administration regulations on everything from health care to the Clean Power Plan.

Pruitt is expected to win congressional approval to head the EPA. But the stage is set for enormous clashes ahead with environmental advocates, who are already questioning whether he should recuse himself when dealing with issues that he has sued the EPA over, like the Clean Power Plan and the Waters of the United States rule.

Environmental advocates argue his nomination effectively invites the fox to guard the henhouse. They point to the fact that Trump's energy adviser, Harold Hamm, the CEO and chairman of Oklahoma-based Continental Resources, served as the chairman of Pruitt's re-election campaign in 2013.

In 2014, Pruitt joined the Domestic Energy Producer's Alliance in a lawsuit against the federal government as it prepared to determine the protective status of more than 200 animal species. Hamm, who chairs the Domestic Energy Producers Alliance, was concerned about one species in particular: the prairie chicken.

If added to the endangered species list, Hamm was quoted in The Wall Street Journal in 2013 as saying the move could foreclose development of some of "the most promising land for oil and case leases in the country."

There are few examples of the coziness between state government officials and big energy companies that are quite as brazen, however, as the relationship that The New York Times revealed between Pruitt and one of Oklahoma's largest oil and gas companies, Devon Energy.

Through open-records requests, the Pulitzer-Prize winning investigation uncovered a letter from Pruitt to the EPA that was drafted by Devon Energy. The letter argued that regulators were exaggerating the amount of methane emissions from natural gas production.

Pruitt argued that the EPA calculations were wrong and that their methodology could inflict economic harm on an industry that is "critically important to the state of Oklahoma."

Pruitt's letter was sent on state stationery to the EPA with a mere 37 words changed from the original draft that Devon Energy provided to attorney general's office. He later told The Journal Record, an Oklahoma newspaper, that it "should come as no surprise that I am working diligently with Oklahoma energy companies, the people of Oklahoma and the majority of attorneys general to fight the unlawful overreach of the EPA and other federal agencies."

Though he has not been an active voice on the earthquake issue, as attorney general Pruitt has not shied away as attorney general from the issue of hydraulic fracturing.

He offered a preview in 2014 of how he as EPA chief might approach matters related to fracking as EPA chief. At the time, he wrote the EPA's Office of the Inspector General questioning its motives as it prepared to investigate the ability of the EPA and states to effectively manage potential threats to water resources from hydraulic fracturing.

"I am concerned that this project is politically motivated and ignores the EPA's three previous failed attempts to link hydraulic fracturing to water contamination," Pruitt wrote, calling the study "unnecessary and duplicative."

"In addition the U.S. Department of Energy has investigated hydraulic fracturing's potential harm to water supplies and found no evidence linking the drilling technique to groundwater contamination," he said.

Pruitt, who has railed against federal interference in what he sees as a state matter, argued that the proposed investigation "appears to be yet another attempt to transfer regulation of hydraulic fracturing from the states to the federal government."

In December of 2016, the EPA released its final report on the issue. Their main finding: "EPA found scientific evidence that activities in the hydraulic fracturing water cycle can impact drinking water resources under some circumstances."

Lowering the risk

While Oklahoma's earthquake issue is far from settled, two Stanford scientists recently published a study predicting the wastewater injection cutbacks requested by the Oklahoma Corporation Commission, coupled with the decline in commodity prices -- which has reduced the amount of new wells being drilled -- would lower the risk of another huge earthquake in Oklahoma.

Industry defenders note that Oklahoma already had a broad network of fault lines and experienced two earthquakes in the 5.0 magnitude range in 1918 and 1952.

But 2016 data from the US Geological Study and the Oklahoma Geological Survey noted that from 1978 to 1999, Oklahoma only had an average of 1.6 earthquakes per year with a magnitude greater than 3.0.

In the Sierra Club lawsuit in federal court against four large energy producers in Oklahoma, they note that the number of annual earthquakes has increased from a maximum of 167 before 2009 to 5,838 in 2015.

(The 2016 Sierra Club suit, which remains active and was filed under the Resource Conservation Recovery Act, asks for a moratorium on wastewater injection over active fault lines. At least one of the defendants has filed a motion to dismiss the lawsuit.)

The chance of having an earthquake of magnitude 6.0 or more in north-central Oklahoma is now above 10%, "similar to the chance of damage at high-hazard sites in California," according to the 2016 USGS report.

In the next few years, the rules and regulations on hydraulic fracturing and related activities could be shaped by a wide array of federal agencies under the Trump administration, including the EPA, the Department of Interior, the Bureau of Land Management and others.

Bracing for Pruitt's potential changes if he is confirmed as head of the EPA, many environmentalists believe their best avenue for challenging the administration and its allies will be through the courts.

"The fact that Scott Pruitt raked in money from oil and gas companies while ignoring Oklahoma families who needed protection from fracking-induced earthquakes destroying their homes is a sneak preview for what he'd do -- or not do -- as EPA administrator," said Michael Brune, Executive Director of the Sierra Club. "Pruitt's long record of siding with polluters instead of American families and communities means he's not just unfit to serve at the EPA, he's dangerous."

Trump has shown no sign of backing away from Pruitt. A spokesman for his transition team didn't comment.