It’s been a big winter for earthquakes in West Texas. A string of small tremors rocked Midland County on December 15 and 16, followed a week later by a magnitude-4.5 quake, the second-strongest to hit the region in the last decade. Then a magnitude-4.2 quake shook the town of Stanton and another series of small earthquakes hit nearby Reeves County.
That’s an unsettling pattern for a state that, until recently, wasn’t an earthquake state at all. Before 2008, Texans experienced just one or two perceptible earthquakes a year. But Texas now sees hundreds of yearly earthquakes of at least magnitude 2.5, the minimum humans can feel, and thousands of smaller ones.
The reason why is disconcerting: Seismologists say that one of the state’s biggest industries is upsetting a delicate balance deep underground. They blame the oil and gas business — and particularly a technique called wastewater injection — for waking up ancient fault lines, turning a historically stable region into a shaky one, and opening the door to larger earthquakes that Texas might not be ready for.
The state is finally trying to change that. In December, the Texas Railroad Commission — the state agency that regulates oil and gas operations and no longer has anything to do with railroads — suspended wastewater injection at 33 sites across a region where more than half a million people live. This is a notable turnaround for the Railroad Commission, which until recently did not acknowledge a link between oil and gas operations and earthquakes, and might be a sign of just how serious the earthquakes have gotten.
Historically, Texas has been seismically sleepy. Its fault lines have lain mostly dormant for eons. “At some point, Texas was a plate boundary,” Heather DeShon, chair of the Department of Earth Sciences at Southern Methodist University in Dallas, told Vox. “All those faults are still present. They’ve just been buried by 300 million years of sedimentation, the formation of the Gulf of Mexico, and building new mountains. So they’re very deep, but they’re still there.”
When faults are active, as they are in earthquake zones like California and the Pacific Northwest, explained DeShon, they constantly put out energy. Rocks in those faults deform for years before breaking in an earthquake. “When you’re no longer on a plate boundary, that constant reloading and breaking of energy doesn’t happen anymore. But some amount of energy was left over on those faults,” DeShon said. The injection of wastewater can help release it.
Early signs of trouble came in 2008, when Dallas-area residents felt a series of small earthquakes that originated in the nearby Fort Worth basin. More earthquakes followed, and a magnitude-4 quake hit a town southwest of Dallas in 2015. No damage was reported, but according to the US Geological Survey, the impact of a magnitude-4 earthquake can include: “Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.”
Earthquakes in West Texas increased from a grand total of 19 in 2009 to more than 1,600 in 2017, according to a 2019 study, coinciding neatly with the rise of wastewater injection in the area. Nearly 2,000 earthquakes hit West Texas in 2021, a record high. According to the TexNet, the University of Texas’ earthquake catalog, 17 of those were magnitude 4 or higher.
It’s hard to overstate just how important Texas is to American oil and gas production. The Permian Basin, which spans West Texas and eastern New Mexico, is responsible for 40 percent of American oil production and 15 percent of the nation’s natural gas supply, with tens of thousands of wells dotted across the landscape. Hydraulic fracturing, also known as fracking, is the most common drilling method in the Permian.
Both traditional drilling methods and fracking can cause the same problem: Each year, drilling releases billions of gallons of briny, salty wastewater that has been trapped underground for millennia. The water flows back to the surface along with oil and gas (and, in the case of fracking, the additional water used to force oil and gas out of shale). That water has to go somewhere, and for decades the conventional wisdom has been to simply re-inject it deep into the ground, at some site that doesn’t get in the way of oil and gas wells.
Often, that water is injected into deep aquifers that often sit on the edges of fault lines. Injecting more water into those aquifers, DeShon said, is a bit like sitting on an old mattress that has a cup of water balanced on one end. The added pressure upends the balance of things, and the cup might fall over — which, in this metaphor, means a fault could slip and release energy in an earthquake.
In regions where wastewater injection receded, mostly because oil and gas operations in the area became less profitable, earthquakes dropped off too. But fracking continues to pick up, generating more wastewater that can lead to more earthquakes.
Oil and gas companies say they support the Railroad Commission’s restrictions, which mirror steps Oklahoma regulators took when they clamped down on disposal operations in 2014 after years of injection-induced earthquakes in that state. “None of us want any seismic activity, and so we support that action,” Ben Shepperd, president of the Permian Basin Petroleum Association, told the Houston Chronicle. But Shepperd praised the Railroad Commission for limiting its regulations to specific wells, rather than “painting the whole area with a broad brush.”
So far, none of the earthquakes triggered by wastewater injection in the Dallas-Fort Worth region or around the Permian Basin have been blamed for injuries or damage to buildings. “We should count ourselves lucky that cities such as Stanton have not been truly battered by a serious earthquake but we can’t keep counting on that good fortune,” wrote the Houston Chronicle’s editorial board recently.
DeShon also argued that there’s still reason to worry. “Once you have started having earthquakes in an area, the earthquake hazard goes up,” she said. “There’s still a lot of unknowns in such a complex system.”
One unknown that remains is where the wastewater ought to go. The Texas Railroad Commission is part of a consortium studying new ways to recycle water produced from drilling, a spokesperson told Vox. For now, the spokesperson added, operators of wastewater disposal wells “can apply to amend their permits for shallow injection and plug deeper portions of such amended disposal wells.” At least one disposal well operator has already had their permit amended.
Then there’s the question of wastewater injection in parts of the Permian Basin that the Railroad Commission hasn’t restricted yet. If bigger earthquakes shake populated areas, DeShon said, Texans won’t be ready for it — the infrastructure was made with tornadoes in mind, and most Texans don’t know what to do in the event of an earthquake.
“My personal opinion is that any community that has been experiencing earthquakes — and we’ve seen the earthquake size increase — should not be scared, but they should be informed about what to do in an earthquake,” DeShon said. “They need to know to drop, cover, and hold on. You don’t run out of buildings, you don’t stand under doorways. You wait until the shaking stops. There’s this education component that needs to happen, and I don’t know that it is.”