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Big West Texas earthquake highlights new seismicity rules

Daniel Foster
Via Flickr (CC BY-NC-SA 2.0)

The tremor started in an area that regulators watch closely.

Texans from San Antonio to Dallas felt the effects of an earthquake that started in far West Texas on Wednesday. The 5.4 magnitude quake was the third-largest tremor that the U.S. Geological Survey has recorded in Texas.

The earthquake occurred in an area that the Railroad Commission of Texas keeps close tabs on. That’s because of the high volume of wastewater from fracking that gets injected into the ground there – a practice that can induce earthquakes.

Hugh Daigle, an associate professor in the petroleum and geosystems engineering department at the University of Texas at Austin, spoke to the Texas Standard about efforts to reduce seismic activity in the area. Listen to the story above or read the transcript below.

This transcript has been edited lightly for clarity:

Texas Standard: After this earthquake, you sent out a series of tweets about how the epicenter of the quake fell within something called a seismic response area. What is that?

Hugh Daigle: Yeah, that’s a good question. So the Railroad Commission has developed a bunch of these seismic response areas in West Texas, and this particular one is the Northern Culberson-Reeves seismic response area, which is from the counties that it’s located in. And that’s an area where there’s been a lot of earthquakes that they believe are associated with disposal of water that’s produced from oil and gas operations in the area. And this is an area where they’re very carefully looking at permitting of water disposal wells in an effort to completely reduce any magnitude 3.5 or higher earthquakes within 18 months of the implementation, which was in March of this year.

Just to avoid any confusion, the Railroad Commission is the agency that regulates the oil and gas industry in Texas. So this region, if I understand what you’re saying correctly, this was established specifically to reduce the number of earthquakes that were induced by fracking, right?

That’s exactly right. So between Jan. 1 of 2017 and Oct. 20 of 2021, they recorded 42 of these events greater than magnitude 3.5. And based on the locations of those events, they drew a contour map around the east and established this area. And they said, “okay, this is a problematic area and we need to address the seismicity that’s going on here.”

Got it. So just for clarification, we’re not talking about the fracking itself. We’re talking about what the companies are doing with wastewater. Now, just to be clear, what, if anything, is actually triggered by this earthquake occurring within this seismic response area? 

So over the years, my colleagues at the Bureau of Economic Geology here at the University of Texas have mapped a series of, actually, a large number of faults that are not currently active. And what happens when you inject water, you increase the pressure that’s within the rocks. And when you change that pressure, you can actually reactivate some of these faults. And that’s what causes an earthquake.

What kind of impact might this ultimately wind up having on the local oil and gas industry? I mean, are we looking at the probability, possibility of new regulations on fracking activities or what? 

Well, that’s an interesting question. So per the stipulations of this seismic response program, actually, there’s no specific action that anybody needs to take as a result of this earthquake, because there are none of these deep injection wells that are close enough to the epicenter of the earthquake. So it’s going to be interesting to see if maybe we do need to have some more regulations that come out of this. But interestingly enough, right now, it doesn’t look like there needs to be any change in behavior per the regulations that we have.

Do I understand you to say that it didn’t appear that the fracking water, the wastewater, caused this earthquake or seemed to be directly related to it?

Well, you know, it’s really difficult to establish causality in this type of situation. And I’m sure in the coming months and years, we’ll see some detailed studies to try to figure out what really happened. The depth of the earthquake is certainly consistent with being triggered by some of these deep injection wells. The closest one is about 9 to 10 miles away from the epicenter, and it’s not inconceivable that the pressure could have propagated that far. But again, like I said, it’s really hard to pinpoint one specific event on this type of activity.

Then what does the future look like when it comes to seismic activity in this part of West Texas? 

Well, we know that there was a large earthquake, the Valentine Earthquake back in the 1930s, which was considerably farther south from where we are. There was a magnitude 5 in this area back in 2020. And I think it’s reasonable to assume that the high amounts of water being injected – I mean, we’re talking hundreds of thousands of barrels per day, so millions of gallons per day going down these wells in this particular area – it’s reasonable to assume that that is going to have some effect on what’s going on in the subsurface. And I think it’s really important to know that some of that is just very poorly understood at this point.

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Michael Marks