Hydraulic fracturing, or “fracking,” (a drilling process that injects millions of gallons of water, sand and chemicals under high pressure into a well, cracking the rock and to release natural gas and oil) has only been known to rarely cause earthquakes.

But the disposal of drilling wastewater used in fracking has now been scientifically linked to earthquakes. The fluids used in fracking (and the wastewater that comes back up the well) is disposed of by injecting it into disposal wells deep underground. This is generally regarded as the safest, most cost-efficient way to get rid of it. But in some parts of the country, especially in the Barnett Shale area around Dallas-Fort Worth, it has also been causing earthquakes. And they’re growing both in number and strength.

How Fracking Disposal Wells Can Cause Earthquakes

The culprit of earthquakes near fracking sites is not believed to be the act of drilling and fracturing the shale itself, but rather the disposal wells. Disposal wells are the final resting place for used drilling fluid. These waste wells are located thousands of feet underground, encased in layers of concrete. They usually store the waste from several different wells.There are more than 50,000 disposal wells in Texas servicing more than 216,000 active drilling wells, according the the Railroad Commission. Each well uses about 4.5 million gallons of chemical-laced water, according to hydrolicfracturing.com.

“The model I use is called the air hockey table model,” says Cliff Frohlich, a research scientist at the Institute for Geophysics at the University of Texas at Austin. “You have an air hockey table, suppose you tilt it, if there’s no air on, the puck will just sit there. Gravity wants it to move but it doesn’t because there friction [with the table surface].”

But if you turn the air on for the air hockey table, the puck slips.

“Faults are the same,” he says. If you pump water in a fault, the fault can slip, causing an earthquake. “Scientists in my community know that injection can sometimes cause earthquakes,” Frohlich says.

The science linking manmade earthquakes to the oil and gas industry isn’t anything new. Decades ago, researchers even found they could turn earthquakes on and off by injecting liquid into the ground, says Dr. William Ellsworth with the Earthquake Science Center of the U.S. Geological Survey.

“This was seen as validation of the effective stress model,” he told StateImpact Texas. “This is work that was published in Science magazine and many other publications.”

The quakes are linked to drilling in Barnett Shale. The productive portion of the Barnett Shale is located directly beneath Johnson, Tarrant and western Dallas counties, about a mile and a half underground. The shale contains an estimated 40 trillion cubic feet of natural gas, making it the largest onshore natural gas field in Texas and potentially in the United States.

A University of Texas at Austin from study last summer found a definitive link between earthquakes in the Dallas-Fort Worth area and disposal wells in the Barnett Shale.

And an earlier study by scientists at Southern Methodist University (SMU) and UT found links between disposal wells near the DFW airport and induced earthquakes for a series of quakes in 2008 and 2009. The study specifically looked at two injection wells in the area that were built in 2008. Seven weeks later, earthquakes started. “Were the DFW earthquakes natural or triggered by activities associated with natural gas production, most likely saltwater injection to dispose of brines?” the report asked. The study said yes, the “correlations are consistent with an induced or triggered source.”

The quakes studied from that two year period were all 3.0 magnitude or below, but in the years since there have been several quakes above 3.0 in the area, going as high as 3.5. There have been more than fifty earthquakes in the area since 2008.

It’s important to note that the earthquakes haven’t caused any reported significant damage. Generally an earthquake has to be magnitude 4.0 or higher to cause damage. But locals in the Dallas-Fort Worth area are disturbed and concerned about the trend of manmade seismic activity.

And there’s the open question of what kind of damage these induced quakes can do to drilling infrastructure. It’s plausible that the tremors could affect well integrity, Frohlich says. “In my business, you never say never. That said, most of the time these earthquakes are not right near the well. But it’s possible an earthquake could hurt a well,” he says, though he knows of no instances where that’s occurred.

It’s also important to note that there a tens of thousands of injection and disposal wells in Texas, yet only a few dozen of them are suspected of inducing quakes. It’s also true that disposal and injection wells have been known to induce seismic activity since the 1960s. What’s happening now is that with the rise of fracking, there is a need for more disposal wells. And in areas where fracking waste water is disposed of near population areas, it’s going to be noticed more.

South Texas experienced a magnitude 4.8 earthquake in Oct. 2011 near the Eagle Ford Shale Play, which is home to over 550 gas wells. There have been many other earthquakes linked to injection wells in the Dallas-Fort Worth area, over 50 since 2008. There were no earthquakes before then. The most recent quake was 3.0 magnitude on January 22, just outside the DFW airport. You can read about other recent quakes in the stories below.

And the quakes aren’t limited to Texas. Ohio experienced a magnitude 4.0 earthquake earlier this year near the town of Youngstown. The New York Times reported that Ohio officials believe this quake, the eleventh such event in Youngstown in 2011, was the result of disposal wells. Ohio stores much of Pennsylvania’s fracking waste in those wells.

Art McGarr, of the US Geological Survey’s Earthquake Science Center, has been looking at whether the amount of fluid stored in a disposal well affects the strength of an earthquake. The question is that as wastewater stays in the disposal wells longer and more and more fluids are added, will the quakes become stronger? McGarr predicts that they will.

“I think we’re at the point when, if you tell me that you want to inject a certain amount of waste water, for example a million cubic meters for a particular activity, I can tell you that the maximum magnitude is going to be five (on the rictor scale) or less. I emphasize or less,” McGarr said in a recent presentation.

Dr. Cliff Frohlich of the University of Texas at Austin is researching the links between fracking and earthquakes. Dr. Cliff Frohlich, Associate Director of and Senior Research Scientist at the Institute of Geophysics at the University of Texas at Austin, says that while just a year ago he would have never said fracking itself causes earthquakes, now he thinks differently. “In the last year there have three well-documented earthquakes that occurred during the frack job and were probably related to fracking. They were all small earthquakes – of a magnitude of 2 or 3 – and, considering, that there are millions of frack jobs, fracking-related earthquakes are so rare,” he told StateImpact Texas.

“The last thing a frack engineer wants is to have the fluids go through a fault and go somewhere,” he said. “It’s like pouring water through a drain. So if you’re a frack engineer’s doing their job, they’re avoiding faults, and they’re trying to bust up area rather than having the fluids move somewhere. People injecting are less concerned about that. They’re trying to get rid of it, so they want a very porous material where fluids can flow away across long distances. So they’re more likely to get to a fault.”

Earthquakes directly linked to fracking have been rare. That hasn’t been the case with disposal wells used to get rid of fracking wastewater, however.

Even if the earthquakes aren’t getting bigger, the growing scientific link between disposal wells and induced earthquakes has made many residents nervous. In response, some policymakers are searching for solutions.

A report out from the National Research Council referenced a nine year-old checklist of best practices for drillers and disposal well operators. That includes investigating the site’s history of earthquakes and its proximity to fault lines. But it included the observation that “government agencies and research institutions may not have sufficient resources to address unexpected (seismic) events.”

At a June 2012 Texas House Committee on Energy Resources hearing, state policymakers heard recommendations on what can be done to mitigate the risk of induced earthquakes. Melinda Taylor was one of the experts to give testimony. Taylor directs the Center for Global Energy, International Arbitration, & Environmental Law. She says other states have more safeguards in place against unwanted earthquakes.

In Ohio, for example, well operators need to do a “fairly detailed analysis of the geological conditions” before the state’s regulatory agency offers a permit to authorize a new disposal well. ”So they can determine whether or not it’s likely to cause problems,” Taylor says.

Taylor also said the Texas Railroad Commission, which regulates oil and gas drilling in the state, may want to consider mandating setbacks, to ensure greater distance between disposal wells and public drinking water supplies, structures, and natural resources.

But as StateImpact Texas reported in January 2013, Texas regulators are largely ignoring the problem.

In a December 2012 forum hosted by the Texas Tribune, Railroad Commission Chair Barry Smitherman said he was aware of what he called “allegations” of a link between disposal wells and quakes.

“I know there are a number of studies being done and I think the University of Texas is doing one, and I’m anxious to see what kind of results we’re going to get,” he said in response to a question from StateImpact Texas. That study was released several months before, in August 2012.

That ‘wait and see’ approach is very close to the public position the Commission has taken previously. In an email to StateImpact Texas, Commission spokesperson Ramona Nye wrote that staff welcomes more data about “theories that hypothesize” a causation between seismic events and injection wells. But the Commission would not make any staff members available for interview.

To figure out how seriously the Commission was taking man-made earthquakes, StateImpact Texas filed open records requests for Commission emails relating to the subject.

The 111 pages of emails the Commission supplied show that staff members there accept what scientists and oilmen have known for decades: Injection wells can cause earthquakes. They even show staff members in communication with EPA researchers over certain quakes. The messages include forwards of media reporting on earthquakes and notes of concern from Texans.

The last email about earthquakes that the Railroad Commission has on record was dated August 6, 2012. There was no record of electronic communication about the quakes that hit the Dallas area in late September, nor about quakes that hit North Texas in October, November or December.

The Railroad Commission is starting the process of writing new rules about disposal wells. But in an email to StateImpact Texas, the Commission said those proposed amendments “do not address seismic activity.”

Frolich, the UT expert on man-made earthquakes, had one last suggestion on how to mitigate unwanted quakes: find new ways of disposing drilling related wastewater.

“If disposal is causing earthquakes you can find a different way of dispose of it. You can dispose of the stuff in a different well, or you can even take it to a fluid treatment plant,” Frolich said.

Of course, companies’ willingness to do that will depend largely on cost and state regulation.
“The people involved in this [disposal well operation] are going to do the cheapest way of doing things that is generally considered safe,” said Frolich.

The above was reported and researched by StateImpact Texas reporters, Kelly Connelly of KUT News, and David Barer and Yana Skorobogatov of StateImpact Texas and Reporting Texas.

Shortly before midnight on Aug. 23, 2011, residents of Trinidad, Colorado and surrounding communities were startled when the ground started shaking beneath them, knocking bricks and stones loose from buildings. Fortunately, no one was injured. As far as earthquakes go, the 5.3 event and the aftershocks that followed were relatively mild.

Nevertheless, the Trinidad quake raised anxiety for another reason. The U.S. Geological Survey eventually concluded that it probably was a man-made quake, caused by the disposal of waste water produced by the oil and gas industry.

While the fracking boom in recent years has provided an economic boost to the United States and increased its energy independence, some worry that there’s a potentially catastrophic downside, if the process adds to the waste water that’s lubricating earthquake faults.

And while most of the quakes linked to waste water injection wells have been small to moderate in intensity, some worry that one eventually could trigger a major quake that might seriously damage buildings and important infrastructure, and endanger people as well.

In oil-and-gas-rich Oklahoma, for example, where the rate of quakes increased by 50 percent between 2013 and 2014, the U.S. Geological Survey and state officials issued a May 2014 alert to residents that the state had an increased risk of a 5.5 magnitude quake or greater, and pointed to waste water injection wells as a likely explanation for the heightened seismic risk. (From Michigan Technological University, here’s a chart explaining what risks are posed by various magnitudes.)

It’s been known for a long time that humans could induce earthquakes by pumping fluids underground. Back in 1962, the U.S Army injected toxic waste fluids into a deep well at the Rocky Mountain Arsenal northwest of Denver, but then stopped after the area was rattled over five years by more than 1,500 quakes, including one that shook chandeliers at the state Capitol and forced legislators to take cover.

But those worries have risen because of fracking. Seismologists’ big concern is not the fracking process itself, but what what operators do with the enormous quantities of waste water that flows back out of the well afterward. Some of that water, which is salty and contaminated with chemicals used in the fracking process, is treated and reused in fracking. But much of it is too contaminated for reuse and has to be trucked or piped to other sites, where it is injected into storage wells that are drilled thousands of feet deep into the Earth.

There are about 30,000 such waste water injection wells across the nation. USGS research geophysicist Justin Rubinstein, who worked on the study of the 2011 Colorado quake, explains that injection wells have a potentially much greater seismic impact than the fracking process itself, because fracking wells tend to be short-lived. Injection wells, in contrast, may last for years and receive a far greater quantity of water, and not just from fracking.

In California, where a just-released study shows that fracking has been used in half of the state’s new oil and gas wells over the past decade. The state, which is crisscrossed with a complex system of large and small faults, has more than 1,500 active waste water wells, according to a March 2014 report issued by Earthworks, the Center for Biological Diversity and Clean Water Action. According to the environmental groups, more than half of those wells are within 10 miles of an earthquake fault, and six percent of them — 87 wells — are within one mile.

In a panel at the Seismological Society of America’s May 2014 annual meeting in Anchorage, several prominent earthquake researchers said that disposal of fracking waste water may also pose a serious risk in parts of the Southwest and Midwest where faults have not been mapped as extensively as California’s.

Gail Atkinson, an earth sciences professor at the University of Western Ontario, said that in addition to waste water disposal, the fracking drilling process itself also poses an earthquake risk — but only for smaller quakes, with a magnitude of up to 4.

The risk might be reduced if the oil and gas industry is able to reduce the amount of fracking waste water that it needs to put into injection wells. One company has developed a system that uses gelled propane instead of water. Because the fluid merges into the oil and gas being extracted, it could eliminate the need to drain away waste water. Friction-reducing additives also eventually could allow operators to keep reusing the same water in wells, instead of having to dispose of it.