MARIETTA, Okla. -- The ground had been shaking for a week, on and off, when the biggest of the earthquakes hit.
People here heard two loud booms. Then the picture frames started falling. Wendy Gillham turned to see her flat-screen television crash to the floor only a foot or so from her infant girl. Then she looked outside and saw her chimney in pieces on her driveway.
"I was a wreck," she said of the panicked moments that day in late September.
Suspicion in this southern Oklahoma community near the Texas border focused on a new neighbor just across Interstate 35, an injection well for disposal of oil and gas wastewater. When the well shut down a few days later, the shaking stopped.
"What else could it be?" Gillham said, unloading groceries and children on a recent afternoon, standing on the drive where the chimney fell.
The earthquakes and the facility blamed for triggering them were the starkest examples yet of seismic bursts being linked to a surge in oil and gas activity in Oklahoma.
People in Oklahoma are not used to earthquakes, or at least they didn't use to be. This is tornado country. Earthquakes are for Californians.
"It's something unreal," said Herschel "Bub" Peery, a county commissioner here.
But they're getting more real every day for some in Oklahoma.
Since 2009, nearly one out of every 10 earthquakes in the contiguous United States has been in Oklahoma, according to an EnergyWire analysis of U.S. Geological Survey data. The analysis looked at onshore quakes of magnitude 3.0 or greater, the strength at which most earthquakes can be felt and reliably recorded.
The 240 quakes here during that time rank Oklahoma No. 2 for seismic activity among the lower 48 states, after California.
Most of the state's quakes can be grouped into four seismic outbreaks since early 2009 that academics and researchers of various stripes have linked to oil and gas activities, primarily deep underground injection of drilling wastewater.
There's the Jones swarm, named after a northeastern suburb bordering Oklahoma City where oil comes up, along with millions of gallons of water that then gets reinjected underground. Hundreds of small quakes have been recorded in the area since 2009 (EnergyWire, Nov. 5).
Then there was the state's biggest earthquake in 2011, a magnitude-5.7 rupture east of Oklahoma City near Prague that produced dozens of aftershocks. A study linked it to two injection wells near the epicenter (EnergyWire, July 24, 2012).
The ground shook through much of October near Enid, in northwestern Oklahoma, where some of the state's highest-volume injection wells are located. That followed the September shaking here in Love County, about 100 miles south of Oklahoma City, where Marietta is the county seat (EnergyWire, Oct. 2).
It's gotten bad enough that the U.S. Geological Survey in October declared that the state is in the midst of an earthquake "swarm," linked at least in part to injection. That prompted the state's elected insurance commissioner to recommend that state residents buy earthquake insurance (EnergyWire, Oct. 31). Some residents say the increase in earthquakes has made such insurance too expensive to obtain.
Studies and skepticism
Other states have also seen an increase in earthquakes amid a boom in oil and gas production across the United States. That boom has been driven by advances in hydraulic fracturing technology that creates millions of gallons of wastewater. Much of that fluid gets injected underground.
State officials and researchers have linked injection of drilling waste to quakes in Arkansas, Colorado, Ohio and elsewhere. In Texas, a recent series of quakes northwest of Fort Worth has some local elected officials questioning whether deep injection of drilling waste might be to blame.
But for whatever reason, the phenomenon has been particularly acute in Oklahoma. Local suspicions have been confirmed in peer-reviewed research by scientists at the University of Oklahoma, the University of Memphis, Columbia University and USGS.
Linking earthquakes to drilling, though, has been tough to accept for many Oklahomans. While they're not used to earthquakes here, they're quite accustomed to pump jacks and deep injection wells. Oklahoma is dotted with more than 4,500 such wells. Oil and gas is a pillar of the economy and provides a lot of solid paychecks in the state.
Skeptics note that drilling and injection had been going on for decades before the ground shaking of the past few years.
Oklahoma officials haven't accepted the findings, even when they came from a professor, Katie Keranen at the University of Oklahoma, housed in the same building as the Oklahoma Geological Survey (OGS). Keranen, who has moved to Cornell University, linked the Prague quake to injection.
"There are still many unknowns and uncertainties in regards to seismic activity in central Oklahoma," said Mike Terry, president of the Oklahoma Independent Petroleum Association, in a statement to EnergyWire. "Researchers in Oklahoma, notably Austin Holland with the Oklahoma Geological Survey, have repeatedly said the increase in seismic activity cannot be fully explained by man-made causes."
Holland is the lead seismologist for OGS, placing him smack in the middle of the debate. He's been so busy with a new outbreak of Jones swarm earthquakes near Oklahoma City that he hasn't been able to finish his report on the quakes around Marietta in September.
He doesn't disagree with the idea that injection wells can cause earthquakes. He authored a peer-reviewed paper describing links between a series of small earthquakes and the hydraulic fracturing of an oil well (E&ENews PM, Nov. 2, 2011).
But he has consistently said the research linking injection wells to particular earthquakes is premature. In the seismology community, Holland and OGS have become the voice of skepticism when it comes to man-made, or "induced," seismicity from injection wells.
When areas around Edmond were rattled by an extension of the Jones swarm in November, Holland posted a report pointing away from oil and gas activities and toward changing water levels in nearby Arcadia Lake. Keranen's research had found links between the Jones earthquakes and the oil production in the area, which produces huge volumes of water.
'You got a lot of big money sitting there'
Still, when Holland investigated the reasons for the shaking around Marietta in September, he focused on the new injection well.
The well belongs to Tom Dunlap, an oilman from nearby Ardmore. He put it just off I-35, north of town, across the highway from Gilham and her neighbors.
Dunlap's plan was to accept wastewater, commonly called "salt water," from the growing oil production in southern Oklahoma's Woodford Shale.
Trucks lined up to drop off loads of toxic, briny soup starting Sept. 9 at the well, mundanely named Love County Disposal Well No. 1. The rumbling started six days later.
"The number of earthquakes increased as injection peaked," Holland wrote in his Sept. 30 report on the shaking, "and the earthquakes are coincident in time with injection."
The connection was close enough for state officials that drilling regulators at the Oklahoma Corporation Commission cut the volume Dunlap was permitted to inject by nearly 95 percent.
Dunlap said it didn't make business sense to stay open with such restrictions, so he shut in the well. Another company halted work on an injection well under construction nearby (EnergyWire, Oct. 2.
After that, the shaking tapered off.
Still, Holland was cautious when he appeared at a community meeting held to discuss the quake.
"We can't say whether the earthquakes are due to natural causes and the well was just a coincidence, or whether the earthquakes are caused by the fluid injection in the disposal well," he said, according to a transcript of a television news report.
To Jonny Hickman, that's mumbo jumbo. He lives here, north of town, across Oswalt Road from Gilham and about a mile and a half from the well. He wasn't happy with what he heard from Holland.
"I'm not even a seismologist," Hickman said. "I can tell you what made the earth start shaking.
"Forty-five years I've lived on this hill," said Hickman, 52. "I never felt anything until they started injecting that salt water."
Hickman is among those who sense that state officials are reluctant to link quakes and oil and gas activities for economic and political reasons, rather than scientific ones.
"You got a lot of big money sitting there," said Hickman's neighbor Tony Bartee, who has a crack in his outside wall. "That fracking is a big deal. If they say for sure that's what's causing it, it's gonna cost those boys a lot of money."
Holland says he's letting the science guide his conclusions.
"I do not consider whether I am going to upset one party or another but instead focus on doing quality quantitative and reproducible science," he told EnergyWire.
And not everyone here is convinced that the new injection well triggered the quakes. Peery, the commissioner for this part of Love County, lives not too far away and felt the quakes himself. But he's skeptical of a connection between the earthquakes and the well.
"They're blaming injection wells. I don't really believe it," he said. "A lot of people want someone to blame."
He notes that most of the people who suffered damage didn't have earthquake insurance. Gillham didn't, and the estimate to fix her chimney was $10,000. Earthquake damage isn't covered by standard homeowner policies. That's what irritates him about the situation.
"The insurance companies, they start nitpicking, and it isn't right," he said. "If you have insurance, they should cover it."
Peery says the question of what caused the September quakes might be settled by a controversial experiment that Holland has proposed.
Holland wants to restart injection at the well site to see whether the earthquakes come back (EnergyWire, Nov. 1). He says the test would be stopped before the quakes got strong enough to cause more damage.
But the idea is unpopular among people who live here north of town, closest to the well.
Bartee, eyeing the stairstep crack in the brickwork on the side of his home, says starting up the well again risks more damage.
"When they stopped it and the earthquakes stopped," Bartee said, "that was proof enough for me."