If you’ve been around the Dallas area in the past few years, you may have felt a number of tremors that probably felt foreign to those of us not from California. A recent series of earthquakes rattling the North Texas area has had people asking, “Did you feel that?”
Since 2008, more than 120 earthquakes have been reported in North Texas. Prior to 2008, an earthquake hadn’t been felt in the area since 1950, according to SMU seismologists.
An SMU-led seismology team consisting of two associate professors of geophysics, Matthew Hornbach and Heather DeShon, revealed their findings from the Azle-Reno region of Texas in a brief press conference-style lecture Tuesday afternoon. The lecture was held in Heroy Hall for around 25 attendees.
Hornbach began the lecture with a quick informative brief in which he explained the major potential causes of the earthquakes occurring in North Texas. These causes include natural stress changes, the potential cause of the Texas drought, and the potential change in industry activity involving wastewater.
“The most probable cause of seismicity in this region has to do with the oil and gas activities in the Azle-Reno area during the last few years,” said Hornbach.
In simple terms: Hornbach believes the earthquakes that have struck in North Texas are due to the high volumes of brine (saltwater) being injected in the gas subsurface. The high volumes of fluids being removed is what is driving the significant pressure changes in the affected areas.
Hornbach and DeShon spent the remaining time answering questions from the audience. The first question asked the scientists where this fluid comes from. Hornbach explained that when producing oil and gas, a large quantity of water is produced as a byproduct that needs to be safely removed, which is why it is injected into the ground.
“The [oil and gas] industry went above and beyond on [the data] they have provided,” said Hornbach. “Without that data we could not have done much of this analysis.”
Hornbach iterated that the industry has been on board with the team since day one and that it is looking for possible causes as well.
The seismology team also developed a 3-D model that helps illustrate the pressure changes occurring in the reservoirs, which DeShon took a few minutes to delve into the logistics of. DeShon explained that the water being injected into the ground goes down almost 8,000 or more feet below the surface and therefore does not have any effect on our drinking water.
One audience member raised a question that referenced Dr. Pearson with the Railroad Commission, who casted doubt on the team’s study specifically in its methodology, the information used, and the conclusions they reached. However, Hornbach believed that what Pearson claimed was actually consistent with what the team believed.
“There’s still a tremendous amount of uncertainty in these models,” said Hornbach. “We’ve drawn these conclusions with very limited, but very valuable data, to make our best estimate on what causes the earthquakes.”
This raised even more doubt among the audience. as people began questioning the team’s confidence and overall accuracy of the study. Hornbach couldn’t say with absolute certainty that the cause of the earthquakes is from oil and gas activity, but from a scientific perspective, he claimed that it is the most likely cause.
Another concern raised was the potential occurrence of larger earthquakes that could have catastrophic and damaging effects. While the series of North Texas earthquakes have not reached a magnitude over three, it’s been proven that the occurrence of an earthquake temporarily increases the likelihood of even larger earthquakes following the initial one. Audience members agreed that this poses a real safety hazard to the public as well as Texas infrastructure that is not equipped to withstand earthquakes.
When it comes to addressing seismic hazard, the chances of a catastrophic earthquake happening are not very likely because we are far enough from the plate boundary, according to DeShon. In other words, the earthquakes measured here have smaller fault lengths than a catastrophic earthquake has.
DeShon refused to speculate on the potential risks and damages that earthquakes could cause, especially on the runways at Dallas Love Field airport as well as other highways and HOV lanes which run through affected earthquake areas in North Texas.
“We are very much aware that the Dallas Metropolitan area as a whole has questions about their infrastructure at this time,” said DeShon. “These are concerns that we share.”
In regards to the amount of data they currently have, the seismometers placed in Irving allowed them to capture the most active part of the Irving sequence, but they were not able to capture the same data in the Azle region. However, DeShon mentioned that they are too early in the Irving study to speculate how strongly they are able to determine causes based on their available data.
One of the major factors that has helped this research study has been data on pressure changes over time, which was provided by the industry. Hornbach said that the industry people are scientists just like them, and both parties are looking for the same answers through their respective models.
“Unfortunately so much of science and life is that there’s a lot more we need to know,” said Hornbach. “We just need to work together to combine data sets, and from that we can really mitigate potential geo-hazards.”