IRA FLATOW: This is Science Friday. I’m Ira Flatow. The state of Ohio is not exactly known for its earthquakes, but in 2011 a magnitude 4 quake shook Youngstown. And in 2014, a series of smaller quakes rattled the same area, 77 of them to be precise. And coincidentally, Youngstown, the Youngstown area, is the site of numerous oil and gas fracking operations, as well as sites where wastewater from fracking is injected back into the Earth’s crust.

And research on fracking sites across the country has been pointing to wastewater injection as a stimulus for earthquakes. But get this. Those 2014 Youngstown quakes? They were traced back to fracking itself, not the wastewater, activating faults deep below the Earth that were previously unknown. And in response to the spike in seismic activity, the state of Ohio ordered better seismic monitoring near oil and gas wells, so wells can be shut down if tremors strike.

But how exactly are geologists connecting quakes to human activity? And in the aftershocks of the fracking boom, can we learn to predict and even prevent seismic consequences? We’re in Cincinnati today with two of the researchers who have been studying this problem. Brian Currie, Associate Professor of Geology at Miami University in Oxford. Welcome. Welcome, Brian.

BRIAN CURRIE: Oh, thanks for having us.

IRA FLATOW: And Mike Brudzinski is Professor of Seismology at Miami University. Welcome, Mike.

MIKE BRUDZINSKI: Very excited to be here.

IRA FLATOW: Let’s talk about the fracking. It seems pretty well understood at this point that fracking related activities, Mike, are causing earthquakes. But what makes it obvious? How can we really know that for sure?

MIKE BRUDZINSKI: So the observations from Ohio are very helpful in the sense that we don’t have as many oil and gas wells being hydraulically fractured, and so we can pinpoint the time and location of the earthquakes and how they match up very precisely with the operational activities.

IRA FLATOW: Let’s go back to that 2014 series. You traced a group of quakes back then to fracking wells. Even the US Geological Survey says most of the seismic activities from fracking is actually from the wastewater. So how often can we trace an earthquake back to the fracking itself?

MIKE BRUDZINSKI: So, yeah. In Ohio, we’ve seen a larger number of cases being associated with the hydraulic fracturing process itself, as opposed to the wastewater disposal. But that is somewhat unique to Ohio. There are other places where waste disposal seems to be the primary driver of earthquakes.

IRA FLATOW: And why is this distinction important?

MIKE BRUDZINSKI: So, I think from a regulatory perspective, folks want to try and make sure that they are properly connecting the seismicity with who is responsible for it. And so in a place like Ohio, there is plenty of waste disposal wells, plenty of hydraulic fracture wells. We don’t want to make every company have to deal with this problem, only those that are starting to produce the seismicity.

IRA FLATOW: Give me a quick thumbnail sketch how fracking happens and how the wastewater is involved in that.

MIKE BRUDZINSKI: Sure. So hydraulic fracturing is a process that’s become more popular over the last decade, in the sense that it is a way to stimulate oil and gas production from formations, rock layers, that it would be more difficult to get the oil and gas from, things you’d have to wait very long time frames to get the oil and gas from. And so fracturing those reservoirs allows for folks to collect the oil and gas more quickly. And so the process of waste disposal is when folks are retrieving the oil and gas from these rock layers, down a few miles below the surface, the water that comes back is rather dirty. And so we don’t want that getting into our drinking supply. And so folks are injecting that down, in some cases even deeper than the rocks that they’re harvesting the oil and gas from, to try and keep it away from people.

IRA FLATOW: Now, Brian Currie, your finding is that these activities aren’t necessarily creating new fault lines, but they’re reactivating very old ones.

BRIAN CURRIE: Yes, those faults have been there for, in some cases, billions of years, or at least a billion years in the Appalachian basin where we’re looking at these events. And so primarily you have ancient fault systems that have developed since, like I said, about a billion years ago and younger, as a result of the plate tectonic interactions with different periods of collision and extension that has gone on along the eastern margin in North America. And so those faults are there. They’re underneath and within the same strata where we’re producing oil and gas from and where we’re re-injecting the wastewater in the disposal operations.

IRA FLATOW: Is it basically just taking the friction away from the rocks under there?

BRIAN CURRIE: That’s–

IRA FLATOW: You’re sort of greasing–

BRIAN CURRIE: That is one of the primary ways that these faults are being reactivated. You can think of it as, if you go down the subsurface, any of the little teeny tiny microscopic pore spaces between individual rock fragments and grains is going to have fluid in it. And that fluid is under pressure. Now, when we inject things back into the subsurface and/or do the hydraulic fracturing that is adding hydraulic pressure to the rocks to break them–

IRA FLATOW: Expressing it out, yeah.

BRIAN CURRIE: –those pressures are increased. And so any water that’s under pressure that might be in a fault zone, if you’re increasing that pressure, you just sort of cushion the fault zone to the point where you can have slip on it within the regional stresses that actually exist in the subsurface.

IRA FLATOW: Does it matter what kind of rock is on top of those fault lines?

BRIAN CURRIE: It depends. You know, so you can think of these fault zones as, in many cases, vertical planes within the Earth. And they’re cutting many different zones. And so in some cases they’re cutting the sedimentary rocks that you’re doing the oil and gas extraction and injection into.

And in some cases they’re going way down deep into these igneous and metamorphic rocks in the basement. And we’ve been finding that those areas are the places where the larger events are happening. But they’re also occurring up closer to where the injection and the fracking is going on.

IRA FLATOW: Now, as you learn more about where the area is and what causes the little earthquakes and the bigger ones, can you sort of look at a fault line in advance, or look at an area yet? Are we not at that point, where we say, look, if we do some fracking here– you’re nodding your head up and down.

BRIAN CURRIE: Yes and no.

MIKE BRUDZINSKI: We’d love to be able to say exactly where the faults are, but yeah, the technology is not at that point yet. I think what we’re trying to help with is general areas that have higher risk, versus general areas that have lower risk. That trying to look at where these– as Brian described them, the basement faults, the deeper rock layers that have the much older faults that are more mature and can produce these large earthquakes. If the operations are closer to those faults, the likelihood seems to be larger. And so those are suggestions we can make to industry, to regulators, to point them to areas that have higher risk versus other areas that have had plenty of operational activity and not seen any seismicity.

BRIAN CURRIE: And so in the basins where these are happening– in some places we know where those faults actually live, but in other cases they’re very small. And really, we don’t know those faults exist until they are being reactivated by the induced activities.

IRA FLATOW: You know, Oklahoma has so many little earthquakes they say there are more earthquakes than days in the year, in Okla. 300 a year or more.

MIKE BRUDZINSKI: Days in a century.

BRIAN CURRIE: Yeah.

IRA FLATOW: Is that right? But, do they detect– or these just happen all the time and a lot of them just get passed by?

MIKE BRUDZINSKI: So we’ve been working on this problem lately, to try and better understand how many earthquakes have been happening in Oklahoma. The catalog over the last decade shows, you know, there’s an increase from a handful a year to over 1,000 a year.

IRA FLATOW: 1,000 a year now.

MIKE BRUDZINSKI: Yeah. And part of that comes from trying to improve our ability to detect those small events, right? The largest events we’ve seen lately are in the sort of magnitude 5 range. But trying to better understand the very small earthquakes has been part of the process we’ve worked on.

IRA FLATOW: And do you talk to Oklahoma about this?

BRIAN CURRIE: Yeah.

MIKE BRUDZINSKI: Absolutely. Yeah. So you know, again, as you mentioned, the relationship between hydraulic fracturing itself and earthquakes is something that we’ve focused a lot of our attention on, because it is more rare. So we wanted to better understand it. But we found that, yes, this process is happening in Oklahoma as well. And so we’ve had a chance to talk with regulators and operators out in Oklahoma, too.

BRIAN CURRIE: And it’s a little bit more difficult to recognize those events in Oklahoma, because most of their events are related to the wastewater disposal. So it’s trying to find the smaller and less frequent hydraulic fracturing related events in all that noise.

IRA FLATOW: And you guys do consulting work for the fracking companies.

MIKE BRUDZINSKI: Right. So we’ve been trying to help both the regulatory side, by trying to interact with Ohio Department of Natural Resources, and as we said, in Oklahoma, the Corporation Commission. But yes, we have been working with folks in the industry. We realized that one of the ways to do that is to form a small consulting company. And so that’s been helpful to try and interact better with the industry.

IRA FLATOW: Now, after the earthquakes in 2011 and 2014, as I mentioned before, the state of Ohio got a lot more careful about monitoring the fracking wells, right? Are there other policy recommendations your work could lead to?

MIKE BRUDZINSKI: So I think at this point, we’re trying to help folks recognize that many of these cases, the seismicity starts as swarms of very small earthquakes. And so if you are just waiting for a larger event that might trigger a regulatory response, it’s actually better for folks to look at any potential seismicity early on, at much smaller levels. So for right now, the magnitude threshold in Ohio is 1.5. So you know, this helps folks to see that Ohio has a pretty strict regulatory threshold for earthquakes in the sense that events that you might typically feel are up closer to a magnitude 3.

So folks are trying to make sure this problem is dealt with well before people would feel it. But our recommendation is to look even smaller than that. From the operational perspective, to tell companies, see if you can get out there and monitor events at smaller levels, because that’ll give you some idea larger magnitudes could potentially occur.

BRIAN CURRIE: And it’s important for the companies, if they want to keep doing what they do, because here in Ohio, since we have those relatively low thresholds, the state can come in and shut you down. And so–

IRA FLATOW: Is that right?

BRIAN CURRIE: Yeah. And that has happened here. And so, I think in Ohio we have some of the most stringent regulations in that regard. And because of that, the companies are taking heed of trying to better characterize any problems that they might be having early, such that they can avoid being shut down by the state.

IRA FLATOW: Let’s go to the phones. We have a question from Wyoming. Hi. Welcome to Science Friday.

AUDIENCE: Hi. Good afternoon.

IRA FLATOW: Hey there.

AUDIENCE: Sorry, Ira. I was what they called a treater on a frac crew. So we stood in the frac [? den. ?] And we would actually treat the job. And we’d be going 100 barrels a minute at 8,500 pounds of pressure through a four inch line and through a three.

So when I was in Guthrie, Oklahoma, at night we would stay in a hotel, and you would actually feel the earthquakes, because we’re fracking all around there. So you pump that much, 100 barrels a minute at 8,500 pounds of pressure down four miles, it’s definitely going to crack that rock open. And then you have the sand, so you prop it open to let that oil and gas flow out.

IRA FLATOW: These guys are nodding their heads like they know what you’re talking about.

MIKE BRUDZINSKI: Yeah.

BRIAN CURRIE: That’s the whole point.

MIKE BRUDZINSKI: Well, yeah. I was going to–

BRIAN CURRIE: So when they’re pumping those pressures and those rates down hole to actually break the rock such that there provides a pathway for the oil and gas that is in those very, very impermeable rocks to go flow into the wellbore. So they want to break the rock, you know. And so that’s just part of the process. And there are earthquakes, micro earthquakes, that are associated with that very process. And so for years, I’ve been interacting with folks in industry, and they’re like, of course there are earthquakes that are happening, but they’re all in the zone, the places where we’re focused on.

IRA FLATOW: Well, that’s the question. Does it matter that you have all these tiny earthquakes?

BRIAN CURRIE: Well, I think so, because you’re starting to generate large earthquakes way out away from where–

IRA FLATOW: You are.

BRIAN CURRIE: –the targets are, in some cases several kilometers. And so from the perspective of the industry, they’re actually putting energy into the rock to break it. But–

IRA FLATOW: And energy has to go someplace.

BRIAN CURRIE: But they’re breaking it someplace they don’t want it to happen. So it’s been a conversation with the companies, because they don’t want that to happen. Because for some reason, what they’re trying to do is not focused effectively on the horizons that they’re of interest.

MIKE BRUDZINSKI: Yeah, I would add to this caller’s example from Oklahoma that the issue in an area like that is, yes, there’s plenty of hydraulic fracture wells going on in that area of Oklahoma. There are also a large number of very large rate waste disposal wells in that area. And so one of the biggest difficulties we have in areas like that is trying to discern, you know, what is the primary cause?

It looks like there are multiple things that could be generating the seismicity in an area like that. This is why we’ve been focusing on Ohio. It’s much easier to separate what is associated with hydraulic fracturing versus what is a waste disposal.

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios, here in Cincinnati talking about fracking with Brian Currie and Mike Brudzinski. What’s the worst size earthquake that comes out of fracking?

MIKE BRUDZINSKI: So the largest event we’ve seen associated with this waste disposal process has been a 5.8, 5.9, depending on who you ask in Oklahoma. And so this is at a level where we are concerned about damage to buildings that could potentially injure people. And so I would echo what Brian said earlier. While, yes, many of the events associated with these activities are quite small, we want to make sure that we prevent these larger events.

And so it does appear that regulations have had an influence. There has been regulations in place now in Oklahoma to reduce the volumes that are being injected at waste disposal wells, as well as to reduce the earthquakes associated with the hydraulic fracturing process. And the number of earthquakes has come down over the last couple of years.

IRA FLATOW: Let’s, go to the phones to Carolyn in California. Hi, Carolyn.

CAROLYN: Hi there.

IRA FLATOW: Hi there. Go ahead.

CAROLYN: I’d like to know if fracking activity could affect the huge Yellowstone caldera area.

IRA FLATOW: Oh. We have a lot of smiles in the studio here. She doesn’t find it funny, I guess.

MIKE BRUDZINSKI: No.

BRIAN CURRIE: Not at all. And so I would suspect that the amount of energy that you’re putting into the ground in a typical hydraulic fracturing job is several tens of orders of magnitude less than the energy that would be required to erupt a supervolcano in the Yellowstone caldera. So I–

IRA FLATOW: You don’t think so.

BRIAN CURRIE: –I can confidently say that that is not a real problem.

MIKE BRUDZINSKI: Yeah. I mean, you know, there are a couple of things at play here. I think one is that folks are concerned about Yellowstone, that as the discussion has occurred over time about past geologic events associated with Yellowstone, folks see the doomsday scenario associated with Yellowstone, that a very large supervolcanic eruption is a scary thought. But fortunately, this is a process that has only happened very infrequently over hundreds of millions of years.

And so it’s not something we anticipate happening anytime soon. And as Brian described, the energy associated with these processes are so small relative to the energy that would be necessary to generate those kind of movements in a volcano. It’s not something that we’re thinking about in our studies.

BRIAN CURRIE: Yes. And I don’t mean to make light of the question.

IRA FLATOW: But, you know, it’s interesting that Brian, you mentioned that the industry is saying, why are you so surprised?

BRIAN CURRIE: Well–

IRA FLATOW: –you’re–

MIKE BRUDZINSKI: No, that’s not–

IRA FLATOW: –mucking around with the stratum.

BRIAN CURRIE: No.

IRA FLATOW: What do you expect to happen?

BRIAN CURRIE: That’s really not true.

IRA FLATOW: No?

BRIAN CURRIE: Because I have a very good friend who works in an oil and gas company, and I went out and gave a talk at his company last spring. And he was like, I can’t believe that this is actually happening. Because we know that we break the rock, but we didn’t know that we’re actually making earthquakes someplace out away from where we’re trying to increase the permeability in our rocks. So yes, it’s something that the industry is very interested in, because it’s not something that they are trying to do at that scale.

IRA FLATOW: And they’re probably surprised how far away–

BRIAN CURRIE: Absolutely.

IRA FLATOW: –their local fracking. I mean, so you have bad press for them on all sides. I mean, one of the reasons, I can imagine, is that here you have people talking about their water getting on fire, and now there are all these earthquakes, and little things like that. And then it happens further than this. Well, we’ve run out of time.

BRIAN CURRIE: OK.

IRA FLATOW: And I thank both of you. From Miami University in Oxford, Brian Currie, Associate Professor of Geology, and Mike Brudzinski. Thank you both for taking time to be with us today.

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