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So far this year, Oklahoma has had more earthquakes of a magnitude 3.0 or greater than any other state in the country — including California. More than 200, just since January.
This is a new and remarkable phenomenon. Just five years ago, Oklahoma was averaging only two 3.0 earthquakes a year. Now, it’s averaging one or two a day.
Scientists are saying that oil and gas-related activity, including fracking and wastewater disposal wells in the state, may be partially to blame.
“We see some cases where there is a pretty clear link between fluid injection and the earthquakes,” Austin Holland, a research seismologist at the Oklahoma Geological Survey, told Here & Now’s Robin Young.
In other cases, the link is less clear.
“We may be looking at a combination of factors,” Holland said. “We can tell that sometimes very large rainfalls or changes in aquifer levels can cause earthquakes. Just the natural changes that occur. We could be looking at a combination of that, combined with changes in the amount of waste water that is disposed of and natural stress changes. There are all sorts of different options that we are looking at and things that might be occurring.”
ROBIN YOUNG, HOST:
From NPR and WBUR Boston, I'm Robin Young.
JEREMY HOBSON, HOST:
I'm Jeremy Hobson. It's HERE AND NOW. And coming up, we'll talk with military analyst Andrew Bacevich about U.S. involvement in the crisis in Iraq.
YOUNG: But first, the news making waves and tremors in Oklahoma. Since January, Oklahoma has had 200 earthquakes of a magnitude 3.0 or greater. California has had just 140. Some say it may be related to oil and gas exploration, water used in fracking or the drilling of wells to hold water runoff. Austin Holland is a research seismologist at the Oklahoma Geological Survey. He joins us from the studios of KGOU in Norman. And, Austin, what do you think is going on here?
AUSTIN HOLLAND: A lot of people are saying, well, it has to be due to hydraulic fracturing. Well, fortunately, hydraulic fracturing is a very quick process, and so that's an easy question to answer. And we do see some earthquakes caused by hydraulic fracturing, but we can explain all these earthquakes through hydraulic fracturing. And the reason we can say that is many of these earthquakes are occurring where hydraulic fracturing is not and when hydraulic fracturing is not occurring in those areas. So there are other oil- and gas-related technologies that may be responsible for some of them, as well. But we can clearly say that hydraulic fracturing contributes a small portion to this recent increase. And another question or challenge with the why now question is these technologies - hydraulic fracturing and waste disposal in wells - have been occurring for about 60 years. So the why now question is a very good question.
YOUNG: Right. And just to remind people - hydraulic fracturing is forcing water underground to break up the shale that might be holding under oil or gas. There also wells that are drilled for all this water. So, I mean, it makes sense that this much disturbance in the ground might have repercussions. But as you said, you're looking for other answers, as well. Because why? I mean, tell us more about Oklahoma, in the sense of whether or not it should have earthquakes at all. It's considered pretty stable?
HOLLAND: Oklahoma is considered fairly stable. It's in a continental interior. However, we have a higher earthquake hazard than many of the surrounding states within the mid-continent of the United States.
YOUNG: Yeah. So it's not as if it's unheard of. But this is a swarm, as I hear it's called - a swarm of earthquakes. Now, back to the fracking because, you know, this is what everybody's talking about. There was a report from the U.S. Geological Survey that found that many of - in fact, most of the new earthquakes did take place near some sort of active injection wells. These are the storage wells.
There's a geophysicist, William Ellsworth. He was lead author who wrote, it's completely plausible that high water pressure used in this injection could nudge previously dormant faults out of their locked positions. But again, he's just using the word plausible. You know, a little more on your thoughts on this because you're seeming to agree that some of it is fracking. But why isn't all of it?
HOLLAND: Well, certainly we could be looking at trigger earthquakes from this injection. One of the challenges is a lot of this injection occurs at very low injection pressures. The other thing here is that the earthquake rate change is occurring over a very large area - about 25,000 square kilometers. Most of the time, we see just these rare isolated incidences, where we have earthquakes triggered by deep water injection, generally at higher pressures than what we're looking at in Oklahoma.
YOUNG: In part, you're saying that with the fracking itself - injecting into the shale - you can see, time and place, when that's happening. But it's harder with the wells to really draw the line that a scientist would want to draw because there's so many of them and there's different kinds of injection?
HOLLAND: Yeah. And they've been running for, in many times, decades.
HOLLAND: And so the big question is why now? If they are triggering, what is going on? What has changed in the subsurface?
YOUNG: What do you think it is?
HOLLAND: We see some cases where there's a pretty clear link between food injection and the earthquakes. In other cases, it's a lot more tenuous. We may be looking at a combination of factors. We can tell that sometimes very large rainfalls or changes in aquifer levels can cause earthquakes - just the natural changes that occur.
HOLLAND: And so we could be looking at a combination of that combined with changes in the amount of wastewater that's disposed of and maybe natural stress changes. There's all sorts of different options that we're looking at and things that may be occurring.
YOUNG: Does it change the conversation - the fact that people can actually feel this effect? I mean, fracking's also been a boon to the state. But might it make it a different conversation if, in fact, people start to get frightened because they're feeling this?
HOLLAND: Well, it certainly has changed the conversation dramatically within the state already. But I want to be clear that fracking is a very small contributor to this. Most of the water that's disposed of in these disposal wells that are the more likely candidate for causing some of the earthquakes - that water's actually coming from the production of oil and gas. It's naturally occurring water that comes out as we produce the oil and gas. And so it makes it much more of a challenge to deal with this. We could treat and recycle all the water used from hydraulic fracturing. We can't do that from all of the produced water that comes out with the oil and gas. So it changes the dynamic of this debate significantly if we want to continue oil and gas production here in Oklahoma.
YOUNG: Austin Holland, research seismologist at the Oklahoma Geological Survey, speaking about this swarm of earthquakes that that state has felt in the last few years. Austin, thank you.
HOLLAND: You're welcome. Transcript provided by NPR, Copyright NPR.