Some parts of Oklahoma and Texas now have about the same risk of an earthquake as parts of California, according to the U.S. Geological Survey.
The big difference is, the quakes in Oklahoma and Texas are "induced" — they're caused by oil and gas operations that pump wastewater down into underground wells.
USGS scientists have now published the first maps of these new quake zones, and they're an eye-opener. An eye-opener because 7 million people are now, suddenly, living in quake zones. There are 21 hot spots where the quakes are concentrated; they're in places where, historically, noticeable earthquakes were rare: Texas, Colorado, Arkansas, Kansas, New Mexico and Oklahoma. Ohio and Alabama have also experienced some induced quakes.
A decade ago, an Oklahoman could count the number of noticeable quakes on her fingers. "In this past year, we had over 900," says USGS seismic hazard expert Mark Petersen. "So the rates have surged."
Petersen says induced quakes have become more frequent because there's more wastewater from oil and gas operations around the country that has to be disposed of. Companies pump it down into underground wells, and sometimes that water raises pressure on underground faults that then slip and cause small quakes.
Industry officials say the percentage of waste wells that pose quake risks is very low. But with the rise in hydraulic fracturing (fracking), which produces a lot of polluted water that needs to be disposed of, the overall number of waste wells around the country has skyrocketed.
The new maps also include the risks of natural quakes around the country, as they have in the past. Those risks haven't changed much. But the number of induced quakes has increased tenfold since 2014, according to the USGS.
Petersen notes that most of these induced quakes are not likely to bring down buildings. Most are in the range of magnitude 3 or 4, which are minor. But some are above magnitude 5, which can do serious damage — cause cracks in your house, for example, or in bridges and roads.
"I think that we need help people understand that they do face a risk in these areas of induced earthquake activity," Petersen says, "and they need to take precautions just like people in California do."
Taking precautions against induced earthquakes — such as strengthening buildings or changing insurance rates — might be tricky, though.
Mark Zoback, a geophysicist at Stanford University who studies induced quakes, says: "It's important to recognize the risk that these maps point out, but that risk is going to change depending on what's happening on the ground." Wastewater wells may not be active for more than a few months or a year; after that, they may no longer pose a risk. Meanwhile, it can take years for a state or community to change building codes to make structures more quake-sturdy.
Moreover, some states have started to ban or limit waste wells in these quake zones. "And in the few places where the injection has stopped," Zoback says, "the earthquakes have stopped."
Zoback adds that the boom in oil and gas exploration in some places is dwindling, which would likely mean fewer waste wells and lower risk. On the other hand, wherever the industry drills new waste wells could become the next quake hot spot.
All this makes it hard to anticipate what the future risk will be. Geologists say they need more information from industry to make good predictions.
Justin Rubinstein of the USGS says many companies do share information about their wells, but it's spotty and varies from state to state. "You can get data [from industry] a year, a year and a half after what was going on, and if you are a regulator interested in understanding what's going on, that means a year or a year and a half lag."
He says geologists want to examine areas where wells might be drilled, to look for faults that might make them vulnerable to quakes, but scientists don't usually know where those future wells will be in time to do the research.
"The USGS doesn't make policy," Petersen says. The best the agency can do, he says, is pinpoint the hazards so policymakers can decide what to do.
RACHEL MARTIN, HOST:
In some parts of Oklahoma and Texas, there's now about the same risk of an earthquake as in parts of California. The big difference is the quakes in Oklahoma and Texas are induced. They're caused by oil and gas operations that pump wastewater down into underground wells. As NPR's Christopher Joyce reports, geologists have now published the first maps of these new quake zones, and they're an eye-opener.
CHRISTOPHER JOYCE, BYLINE: An eye-opener because 7 million people are now suddenly living in quake zones. These are places where historically, noticeable earthquakes were rare - Texas, Colorado, Arkansas, Kansas, New Mexico and Oklahoma. A decade ago, an Oklahoman could count the number of noticeable quakes on her fingers.
MARK PETERSEN: In this past year, we had over 900, so the rates have surged.
JOYCE: Mark Petersen is a seismic hazard expert at the U.S. Geological Survey. He says induced quakes have surged because there's more wastewater from oil and gas operations around the country that has to be disposed of. Companies pump it down into underground wells, and sometimes that water lubricates underground faults and causes small quakes. The map shows the risks of natural quakes around the country but now also induced quakes. He notes that most of these man-made quakes are not likely to bring buildings down, but they can do serious damage - cause cracks in your house, for example, or in bridges and roads.
PETERSEN: I think that we need to help people understand that they do face a risk in these areas of induced earthquake activity and that they need to take precautions just like people in California do.
JOYCE: Taking precautions against induced earthquakes, like strengthening buildings or changing insurance rates, might be tricky, though. Mark Zoback is a geophysicist at Stanford University who studies induced quakes.
MARK ZOBACK: It's important to recognize the risks that these maps point out. But that risk is going to change depending on what's happening on the ground.
JOYCE: Wastewater wells may not be active for more than a few months. Moreover, some states have started to ban them in these quake zones.
ZOBACK: And in the few places where the injection has stopped, the earthquakes have stopped.
JOYCE: Which is good news if you live nearby. But Zoback notes that the stop-and-go nature of this wastewater disposal industry makes it hard for citizens and governments to prepare for a quake hazard that may be gone next year.
MARTIN: NPR's Christopher Joyce reporting and Chris joins me now in the studio to talk more about this. So how useful are these maps because as you point out in that piece, the industry varies, right? Like, where this is more likely to happen, this changes year-by-year?
JOYCE: Yeah, it can change year-by-year. And so this is a snapshot of what they know over the past 12 years or so. And what geologists are saying to people is, look, you can prepare somewhat for this. You can send engineers out and look at bridges and then look at roads and look at hospitals, look at schools to see if they're prepared for the future and to see if there's already damage, for example. Things like changing building codes is tough, though, because that takes a long time. And as is obvious from the story, I hope, is that what happens to the oil industry could change where the quakes are going to be next year.
MARTIN: Let's talk about some of the technical aspects of this. What determines where and how much of this wastewater is actually going to be injected into the ground and thus where the quakes are likely to be?
JOYCE: Well, the oil industry and the gas industry - there's always been this wastewater even before hydraulic fracturing started. And I should point out that it's waste wells, it's not the fracturing that does these quakes. But none the less, as fracking has taken off, there's much more of this wastewater - toxic, salty, nasty water that has to be gotten rid of. And what they do is they ship it off somewhere and put it down these wells. But, you know, in some parts of the country, the oil and gas industry is fading - parts of Texas, for example - the boom is ending. In Ohio, the state government has cracked down on some of this waste well disposal. So it's hard to tell where the future is going to be, where the activity is going to be.
MARTIN: So what's the upshot of all of this for authorities in these states but also for residents?
JOYCE: Well, residents need to think about preparing and they need to think about things like making their homes earthquake proof, even though these are small quakes. Geologists are trying very hard to figure out where are the geologically sensitive areas so they can tell the oil industry and the gas industry, don't put your waste wells there. But there's no national program for this. It varies state-to-state. Furthermore, geologists can't just go out willy-nilly and look at the faults and the geology of a local area until they know that there's going to be a wastewater well there. And they don't know. A month from now - or sometimes the industry doesn't tell them until after the waste well has been in for a year.
MARTIN: Are we likely to see more regulation in hopes of being able to predict some of this?
JOYCE: That's up to the states right now or the federal government. I mean, U.S. Geological Survey is putting this information out saying we don't make policy. We just study the Earth. Here's what we know, go do something.
MARTIN: NPR's Christopher Joyce. Thanks so much, Chris.
JOYCE: You're welcome. Transcript provided by NPR, Copyright NPR.