When an earthquake shook Austin in 1902, some thought an explosion in the oilfields of Spindletop, in southern Beaumont, might be to blame.
The 1902 earthquake was naturally occurring. But the link between human activity and earthquakes is very real and well established, said Cliff Frohlich, associate director and senior research scientist with UT's Institute for Geophysics.
"When people make the statement that it hasn't been established that humans can cause earthquakes, they're either woefully uninformed about the research by myself and hundreds of others over the last 70 years or they're trying to mislead you," he said. "That's like people saying the world is flat; that evolution hasn't been proven or that humans can't cause climate change."
Research by Frohlich and others have linked disposal wells and oil and gas extraction to earthquakes in Texas. Most of these earthquakes have been small enough or far enough away from communities that they haven't caused injuries or damage to infrastructure. But some researchers argue an increase in small tremors ups the odds of a big quake.
And while new state regulations make earthquakes a consideration for permitting disposal wells, further research and management could help energy companies develop oil and gas safely.
How It Works
In his research, Frohlich found earthquakes are linked to different steps in oil and gas development in the Barnett Shale around Dallas-Fort Worth and the Eagle Ford Shale in and near the Crossroads.
In studies published in 2011 and 2012, Frohlich found that nearly all the small shakes he looked at in the Dallas-Fort Worth area were near injection wells, where the water and chemicals used in fracking are disposed of underground. But in South Texas, which has a history of earthquakes, tremors were correlated to increases in the rate of pulling oil and water from the ground.
When large amounts of fluid are removed from underground, this may cause settling that can increase forces on nearby faults. That settling appears to be what has caused most of the Eagle Ford Shale quakes since 1973, Frohlich said.
In the case of quakes caused by injection wells, such as those in the Barnett Shale, it is thought that liquid disposed of in the wells can seep into nearby faults, which are near failure but locked into place by friction. The liquid pushes apart the rock-on-rock lock, reducing friction and causes the fault to fail or slip.
Close to Home
On Feb. 19, a 3.1-magnitude earthquake shook Hallettsville and parts of Lavaca County.
Lavaca County Judge Tramer Woytek remembers similar small quakes in the early-2000s and late-'90s, he said.
The epicenter of the most recent quake was northeast of town and resulted in a few calls to the sheriff's office, but no injuries or damage were reported.
The county has emergency management plans to cover natural disasters, including earthquakes, and doesn't plan to change those plans based on the most recent quake, Woytek said.
County officials in DeWitt and Karnes counties also aren't revising their emergency management plans, despite recent seismic activity.
"The relation to fracking and all of this is unproven," said DeWitt County Judge Daryl Fowler.
Typically, where there are hundreds of small tremors, bigger earthquakes hit, said U.S. Geological Survey geophysicist Bill Ellsworth.
"Although the larger earthquakes that we're concerned about are unlikely, the odds are still high enough that we'd be concerned about them from a hazard perspective," he said.
Karnes County Emergency Management Coordinator Susanna Koliba said she's talked to professionals in the field about the odds of a large quake occurring in the county, where several small tremors have occurred.
"It is a concern. And it is something that we are investigating and that we are looking at. But it's not something that we want to alarm people with," she said.
Just because there are a lot of small quakes, doesn't necessarily mean there will be a big one, Frohlich said.
"There are situations where people have a lot of little earthquakes, and all you have is little earthquakes," he said.
That said, if the 4.8-magnitude earthquakes that occurred in Timpson and Fashing, both in rural areas, would have hit Dallas-Fort Worth or San Antonio they could have caused millions of dollars in damage, Frohlich said.
Assessing the Threat
In a study published Feb. 20, Ellsworth and co-authors suggested one way to reduce the hazards of human-caused earthquakes is to have a better map of small seismic activity.
"A seismic network capable of precise locations of small earthquakes could reveal the presence of a large, possibly dangerous, fault being reactivated due to fluid injection," according to the study published in Science magazine. "Information of this sort might prove invaluable for avoiding a damaging earthquake."
Although the Railroad Commission of Texas, which regulates oil and gas in the state, does not acknowledge the link between oil and gas activities and seismic events in Texas, the commission hired a seismologist last April.
The commission's newly hired seismologist, Craig Pearson, helped draft rules related to disposal wells and seismic events adopted by the commission in October, said commission spokeswoman Ramona Nye.
Among the new rules is a requirement that applicants conduct a search of Geological Survey seismic data for earthquakes that have occurred within 100 square miles around a proposed new disposal well.
Small Quakes Not Measured
But a gap in Geological Survey seismic data could make the requirement less effective.
With only a handful of permanent monitors in the state, U.S. Geological Survey data misses most of the tremors under a magnitude of 3, Frohlich said.
In some of his research, Frohlich used data from a National Science Foundation-funded program that leapfrogged broadband seismometers from west to east across the U.S. from 2008 to 2011. During the two-year-period the seismometers were in Texas, there were about 100 monitors in the state.
In the Fort Worth Basin, the Geological Survey data showed eight earthquakes. The temporary monitors showed 64 small tremors during the same period, Frohlich said.
"And that's not because they were missing big earthquakes. It's because we were able to find little earthquakes," he said.
Frohlich and his team identified five to 10 times more earthquakes than the Geological Survey data in the Eagle Ford Shale, too, he said.
Finger on the Pulse
The "TexNet Seismic Monitoring Program," a University of Texas at Austin effort proposed in the state budget, could identify more small quakes in Texas, Frohlich said.
In 2005, there were five permanent seismometers in Texas. If the TexNet program is funded, there would be 38 permanent stations, which could help identify more small tremors. There would also be 36 temporary stations on hand, which could be relocated when a big quake happens to get a better idea of where and at what depth the event took place, he said.
Most seismometers are smaller than a football and cost between $2,500 and $6,000, said Art McGarr, a geophysicist with the U.S. Geological Survey who also participated in the study published Feb. 20 with Ellsworth.
These small devices are key in identifying trouble injection wells and gaining a bigger picture of the danger brewing underground.
If a network of the sort TexNet would create identifies a particular well field is causing small tremors, the U.S. Geological Survey could deploy more seismometers to the area to get precise locations of the quakes, McGarr said.
"In many cases these earthquakes have revealed faults that nobody knew about," he said. "And these faults play an important role in determining earthquakes that can be potentially damaging."
©2015 Victoria Advocate (Victoria, Texas). Distributed by Tribune Content Agency, LLC.
