That's exactly what happened in northern Arkansas, where, according to state geologist Ausbrooks, water from several injection wells pushed apart the two sides of a fault, "allowing it to slip and start popping off the earthquakes"—thousands of them. Ausbrooks, along with Stephen Horton, a University of Memphis seismologist, identified the source: a previously unknown seven-mile-long fault that hadn't budged in modern times. Though not huge, the fault is still long enough to generate a magnitude-6.0 earthquake. (In 1993, when an equal-size temblor hit Klamath Falls, Oregon, it killed two people and caused $7.3 million worth of damage—in a rural area.)
While the largest faults in the United States are documented and mapped—the San Andreas, New Madrid, Cascadia, and dozens of others—"there are faults everywhere, and some are too small to be seen," explains Mark Zoback, a professor of geophysics at Stanford University who was on the National Academy of Engineering committee that investigated the Deepwater Horizon oil spill. "A fault can be missed that could produce an earthquake large enough to cause some moderate damage."
Oil and gas companies say they don't cause quakes but refuse to provide scientists or regulators the data to prove it.
Scarier still is that any fault, no matter how minuscule, can instigate the domino effect scientists have observed during injection-induced earthquakes. "The scenario we worry about is one earthquake spawning another," says the USGS's Ellsworth. This phenomenon was evident in Oklahoma, Keranen says, where "we had one fault-plane go, a second one, and then a third one. They ruptured in sequence." The first tremor in Prague sprang from a minor fault that collided with a larger fault, sparking the quake that trashed Joe and Mary Reneau's home, along with a dozen others.
How far from the site of an injection well could a quake occur? Scientists aren't sure. In Arkansas, along the fault discovered by Ausbrooks, tremors emanated nearly 10 miles. Had those quakes collided with another fault, the shaking might have extended much farther. "Once it starts moving, it's like a chain reaction," notes Ausbrooks.
All these factors were in play in Youngstown, where D&L Energy Group conducted an experiment, burrowing 200 feet into solid rock known as the Precambrian layer, according to Heidi Hetzel-Evans, spokeswoman for the Ohio Department of Natural Resources. Tremors began three months after wastewater entered the well. The strongest, a 4.0, struck on New Year's Eve. Wastewater had seeped nearly 2,500 feet beyond the bottom of the borehole into an unknown fault. "There will be no more drilling into Precambrian rock in Ohio," Hetzel-Evans dryly tells me.
John Armbruster, a seismologist at Lamont-Doherty who was among those summoned to Youngstown, told me, "This well caused these earthquakes. There were no felt earthquakes in Youngstown in 100 years." Within a year of the well opening, there were "12 felt earthquakes. After the well was shut down, the number decreased dramatically. You'd need Powerball odds for that to be a coincidence."
There is no shortage of evidence. After quakes struck near Trinidad, Colorado, in 2011, the USGS set up a monitoring network. "A magnitude-5.3 earthquake occurred within two kilometers of two high-volume injection wells," says Justin Rubinstein, who is part of a new USGS project to study human-induced seismicity. "These earthquakes were caused by fluid injection." Ditto in Dallas; as UT-Austin's Frohlich points out, "These earthquakes could have been anywhere. They weren't. Virtually all of them were near injection wells."
Earthquakes near Prague, Oklahoma, from November 5, 2011, through December 4, 2011. Red indicates 2.2 magnitude; magenta represents the 5.7-magnitude quake. KellyMcD/Flickr
Ellsworth, who peer-reviewed Keranen's study, has researched earthquakes for more than 40 years and is a recipient of the Department of the Interior's highest honor for his contributions to seismology. He studied geophysics at Stanford, earned his doctorate from MIT, and is the former president of the Seismological Society of America. When I asked him if there is any doubt among his colleagues about what produced the quakes in Arkansas, Colorado, Ohio, Oklahoma, and Texas, he replied, "Injection of wastewater into Class II wells has induced earthquakes, including the ones you cite." Rubinstein agrees: "In my opinion, it's pretty clear in all of these cases—Youngstown, Arkansas, DFW, Trinidad, and Oklahoma—that injection wells were the cause."
Does industry concur? Jim Gipson, director of media relations for Chesapeake Energy, operator of the wells under DFW airport and a now-closed well near Greenbrier, Arkansas, declined my request for an interview. Hal Macartney, geoscience adviser for Pioneer Natural Resources, which owns some of the wells implicated in the Colorado quakes, dodged my calls and emails for three weeks. Even those not implicated directly with quake-causing wells are staying silent. Hydrofracking pioneer Norman Warpinski, who works for Halliburton, refused comment. Geophysicist Mark Houston and managing partner Steve Sadoskas, at oilfield-services provider Baker Hughes, wouldn't talk. Julie Shemeta, founder of MEQ Geo, a firm that does seismic consulting for oil and gas exploration, said she was too busy for a 15-minute phone call even though I offered her a two-month window to schedule it.
I'm not the only one getting rebuffed. There is "a lack of companies cooperating with scientists," complains seismologist Armbruster. "I was naive and thought companies would work with us. But they are stonewalling us, saying they don't believe they are causing the quakes." Admitting guilt could draw lawsuits and lead to new regulation. So it's no surprise, says Rubinstein, "that industry is going to keep data close to their chest." When I ask Jean Antonides, New Dominion's VP of exploration, why the industry is sequestering itself from public inquiry, he replies, "Nobody wants to be the face of this thing." Plenty of misdeeds are pinned on oil and gas companies; none wants to add earthquakes to the list.
The USGS's Ellsworth tells me that some operators track seismic data near well sites but won't share it, and so far there is no state or national regulatory requirement to do so. And the "Halliburton Loophole" written into the 2005 energy bill at the behest of then-Vice President (and former Halliburton CEO) Dick Cheney excludes hydrofrackers from certain EPA regulations, among them provisions related to "the underground injection of fluids…related to oil, gas, or geothermal production activities." Upshot: "It's an age where information has exploded, but this is an area where we're still working in punch cards," Ellsworth says.
A cracked wall on the Reneau's property in Prague, Oklahoma. After the November 2011 earthquakes, it took the Reneaus six months to rebuild their home.
Just knowing the daily volumes of water being pumped into a well would yield critical clues. "There is a correlation that shows the largest earthquakes tend to be associated with the largest volume wells," adds Ellsworth. Ideally, the USGS would get real-time data. But operators are only required to track monthly volumes, and those tallies are often delayed six months or more. By then, it's too late. Rubinstein wants "industry to actually give us hourly or daily injection pressures and volume, so we can model where the fluids are going and predict how the stress evolves over time…and be able to come up with some probabilistic sense of how likely you are to generate an earthquake."
As for Keranen's explosive research on the Wilzetta Fault, New Dominion's Antonides is recruiting his own scientists to produce a report challenging it. Meanwhile, he has his own theories. "The traffic driving across the freeway could have caused it," he says, adding that another "trigger point" is the two large aquifers that bracket the fault. Drought has reduced their water levels, "removing a lot of the weight" and allowing the ground underneath to "rebound" and perhaps release energy in a pent-up fault. "All this stuff is tied together—the aquifers, plus trucks driving across the freeway, plus water disposal, plus 50-story buildings—the whole system of man." (This hypothesis has some basis in reality. Scientists in Taiwan fear that the weight of a skyscraper unhinged faults underlying Taipei. Though no such structure, it must be said, is found within 50 miles of Prague, Oklahoma.)
Nine days after the New Year's Eve quake in Youngstown, D&L Energy Group issued a statement that said, "There has been no conclusive link established between our well and the earthquakes. Proximity alone does not prove causation." In March 2012, state officials published a report explicitly detailing the connection, noting that the recent quakes were "distinct from previous seismic activity in the region because of their proximity to a Class II deep injection well. In fact, all of the events were clustered less than a mile around the well." But D&L still questions the new findings—even though the quakes petered out soon after the company voluntarily shut down its well.