November 22, 2022 540 PM
FAR WEST TEXAS — On Wednesday, residents of Presidio County were rocked by the far-reaching effects of a 5.4 magnitude earthquake originating in Reeves County, on the border of Culberson County. The quake could be felt well beyond the tri-county, up to hundreds of miles away, according to data collected by the U.S. Geological Survey’s National Earthquake Information Center.
It was the third largest earthquake in Texas history, data shows, and the largest recorded in the state since 1995. It is also the most striking example yet of a demonstrable increase in seismic activity in the area, known as the Delaware Basin, which this year has seen more magnitude-3 earthquakes than the entire state of California, according to geophysicist Justin Rubinstein, deputy chief of the U.S. Geological Survey’s Induced Seismicity Project.
“It’s pretty significant that these earthquakes are occurring at such a high rate,” said Rubinstein. “And now, there being a magnitude 5.4 — that’s a pretty significant earthquake, and had it occurred in a more urbanized area it could pose the potential for damage.”
The day after the earthquake, the Texas Railroad Commission, which regulates the state’s oil and gas industry, announced that the agency had sent inspectors to the area. It is known that the seismic activity in the area is man-induced, stemming from the disposal of fracking wastewater, and the agency has enrolled mitigation measures in an attempt to ameliorate that activity. In March of this year, the commission launched a response plan aimed at addressing increased seismic activity in the area — called the Northern Culberson-Reeves Seismic Response Area (SRA) — its objective being “to reduce the occurrence of high-magnitude seismicity such that recurrence of 3.5 magnitude events is decreasing by December 31st, 2023.”
After examining disposal practices at injection wells in the area and talking to operators, the commission will take action to reduce seismic activity as outlined in the response plan, per a statement released by the agency — this may include increasing the boundaries of the SRA and requiring a reduction in injection volumes.
Seismologist Heather DeShon, member of the Texas Seismological Network and department chair of SMU’s Roy M. Huffington Department of Earth Sciences, explained that the subsurface pressure changes associated with wastewater injection can travel tens of kilometers from the injection site, so she anticipates an increase of the SRA to account for that expansion. But the effects of any measures won’t be seen immediately, as the timeline for the response plan indicates — the impact of injecting those fluids into the ground will not be spontaneously undone.
“It’s not like a faucet,” she said. “You can’t just turn it off and expect the problem to go away, because you already have modified the stresses, and it’s going to take a while for the system to reach a new equilibrium. So I expect to see continuing earthquakes.”
Rubinstein noted that in the case of last week’s Reeves County event, the earthquake took place outside the immediate vicinity of the nearest injection sites — meaning it could take longer to quell the impact of wastewater injection.
“When you have earthquakes far away from injection wells … it persists for a long time, so even if we were to shut down these wells that are farther away, the pressure effects are going to last a lot longer than it would for wells that are closer to the earthquake,” he said.
It’s difficult to say exactly how long it can take to reach a new equilibrium, DeShon said — that question is the subject of active research among experts. But such mitigation measures as reducing injection volumes can make an impact. The Fort Worth Basin can serve as a helpful case study in this regard — DeShon noted that as volumes were reduced, the magnitude of earthquakes occuring in the area went down too.
Local activists have been sounding the alarm on increased seismic activity in the region for some time, expressing concern that the activity could negatively impact both the quality of groundwater and the flow of San Solomon Springs. Independent researcher Coyne Gibson monitors seismic activity in the area through the USGS and has been pushing for tighter regulations when it comes to fracking and deep injection wells. He expressed concern over the magnitude of last week’s earthquake, which was far-reaching enough to damage a hospital building in San Antonio.
“We should be substantially alarmed,” he said. “This was a major event. It was felt as far away as San Antonio, and damaged the historic structure there. In terms of specifics in [this] region, I can’t cite any damage that’s been recorded. However, we all felt it. We’re quite alarmed by it, based on the data and the physical impact of it.”
Rubinstein recommended that Far West Texas residents acclimate to the reality that earthquake activity where they live is not vanishing — that means familiarizing themselves with what to do in an earthquake, and having a plan in place. It is recommended that those living in a place impacted by earthquakes have enough supplies to last for at least 72 hours; in the event of an earthquake, people should hide underneath a table, if possible, to protect themselves from falling objects.
“People in this part of Texas are now in earthquake country, and people need to be prepared for earthquakes,” he said.