by Carolyn Gramling Thursday, January 5, 2012
During the winter of 1811-1812, three strong earthquakes between magnitude 7 and 8 rocked the New Madrid seismic zone, which runs through parts of eastern Missouri and northeastern Arkansas. The quakes opened deep fissures, destroyed forests and lakes, and produced intense ground shaking that liquefied the soil, turning the land to the consistency of jelly across an area of 10,000 square kilometers. They also became the stuff of legend — legend that has been hard to shake, and has made it difficult to realistically assess the modern hazard in the region, asserts Seth Stein, a seismologist at Northwestern University and the author of a new book, “Disaster Deferred: How New Science is Changing Our View of Earthquake Hazards in the Midwest.”
What makes the hazards related to New Madrid so difficult to pin down is that the seismic zone is in the center of a tectonic plate, rather than along its boundaries. “Intraplate” earthquakes happen around the world, but the mechanisms that cause them to slip are far less understood than those along plate boundaries such as those in California.
GPS studies of ground movements in the region suggest that the current hazard is very low, Stein says — an assessment that has put him at the forefront of an often-heated debate over how people living in the New Madrid region should prepare for future hazards. Citing the potential dangers of future earthquakes, government agencies including the Federal Emergency Management Agency (FEMA) and the U.S. Geological Survey (USGS) have urged the region to adopt more stringent building codes. But Stein has said that those regulations would cost communities billions — and would be unnecessary to boot. New Madrid’s Reelfoot Fault, which slipped 200 years ago, is dying, he says.
In “Disaster Deferred,” Stein delves into both the science and mythology surrounding the New Madrid quakes. He talked with EARTH’s Carolyn Gramling about why he thinks the government’s assessment of the hazards in the New Madrid is overwrought.
SS: I thought there might be two audiences. One was the general public … There is a lot of really scary stuff being stated; FEMA is issuing these forecasts of doom, with thousands of people dead and billions of dollars. So I thought there might be a lot of public interest in it. I also thought there might be a lot of interest among teachers. We’re going to put resources on the Web, including a teachers' guide to the book.
This was my first attempt to write for a general audience. I was hoping to convey how science works, how we learn about the world, how our ideas change, and how we make sensible decisions given what we know.
SS: There’s a widespread belief that this thing wreaked devastation across the U.S. Certainly the biggest myth is that it rang church bells in Boston. And you often see a claim that these were the biggest earthquakes in North America. A popular video called “Hidden Fury” claimed they were the biggest on Earth! But in places like St. Louis or Nashville, what you had was a few cracked chimneys. It’s been claimed that the Native Americans predicted it … there’s a USGS circular called Tecumseh’s Prophecy. That’s another one of these urban legends: That after the earthquake he said, “See, the earthquake is on our side.” A lot of the [modern] forecasts of doom are recycling these old legends.
SS: Yes — it refers to an idea that’s scientifically been dead for a long time but keeps hanging on. Like the church bells in Boston. I did a Google search on this, and I got 32,000 hits for this claim, even though it’s well-known not to be true.
SS: There’s such a vested interest. FEMA is hysterical; it’s planning to have earthquake drills this year. It’s wacky. In a lot of ways what they’re doing this year resembles earlier panics. During the swine flu [scare in 2009-2010], FEMA claimed a million people were going to die. So there’s sort of a pattern. It turns out there’s a phenomenon called “disaster chic.” They will promote these disasters and of course they don’t actually come true.
SS: Yes. The real shocker here, which really surprised us, is that when we started this experiment in 1997, we expected to see motion building up to the next earthquake. [Other teams had] reported results and said they saw motions, but the more we looked, the less we saw. And by now everyone agrees that the motion is either tiny or zero.
SS: We think that the most plausible scenario is perhaps removal of the
sediment loads as the [MississippiCK] River changed course after the
But yes, there are all kinds of faults all over North America. … If you were a billion years old, you’d have a lot of cracks. Any little thing occasionally can move one of them.
SS: It’s unlikely to do anything on a timescale of thousands of years. The history of these kinds of faults is that they are active for a few thousand years, then dormant, then active again.
And this is true for other intraplate earthquakes, such as in China. There’s a neat paper coming out about this happening in northern China. In the last 2,000 years, no magnitude-7 earthquake has happened on the same fault twice. So it’s kind of a neat picture.
SS: All the risk analysts will tell you the same thing — think carefully about rushing off to pay for disaster. The problem is that the preparing costs you something: Do you want to put steel in your school, or do you want to hire teachers? Those are the kinds of questions one needs to think through very carefully.
At this point I would say earthquake preparations in New Madrid should be extremely modest; maybe a few very critical facilities. The more important thing is the government should stop issuing regulations until they’ve looked at the costs and benefits involved. A lot of things make economic sense in California but not in St. Louis. Hurricane shutters are unlikely to make sense in Boston, but make sense in Miami. One should not be doing this kind of thing until the cost-benefit analysis is done.
SS: FEMA has all the wrong institutional incentives. Emergency managers have to keep their agency funded, so they’re always issuing warnings of disaster. I think of this as a continuum, from swine flu to Y2K to this. It’s always the same story. Part of that is the way funding structure works — they don’t have to cover the costs of their predictions. FEMA is telling communities to spend billions getting ready for an earthquake, but somehow we haven’t created a system where emergency management agencies are forced to think of the consequences.
They can overpredict because they don’t bear any of the costs; the costs of compliance don’t come out of their budget. This is a big failure in our whole emergency system: We haven’t incentivized the cost to find the sweet spot. You want to do the right amount of hazard mitigation — not too little and not too much.
SS: USGS has a complicated set of internal dynamics. It’s a very large organization. There are people who believe [that New Madrid is hazardous], and an awful lot who don’t. The official story is that it’s more dangerous than California, but I don’t think a whole lot of people in the agency actually believe it.
Until about 10 to 15 years ago [when we started collecting GPS data for New Madrid], that story made a lot more sense. But not now. In 1996, USGS redefined the earthquake hazards across the United States, from [the maximum possible earthquake] every 500 years to every 2,500 years. It was a conscious change, and it made the hazard wildly higher in New Madrid.
SS: The media has played a role [in the hype]. My sense is the news media by and large don’t believe this themselves, but people want to hear these stories. Many news teasers use the line, “Are you and your family at risk?” Of course, the answer is usually no. We all kind of like scary stories — when we know they’re not real. It’s kind of like Halloween.
I think FEMA’s going to do Halloween this year. I wouldn’t spend any money on [actual hazard mitigation in New Madrid] without thinking it through pretty carefully, but if you treat it as good clean fun, Halloween is harmless. You can enjoy it as entertainment. I tend to view these warnings of disaster as entertainment more than anything else.
SS: The take-home message is that we should think of New Madrid as a very interesting science problem — it’s an intraplate earthquake zone, but it’s not a very large hazard. Based on what we now know, we shouldn’t be rushing off to spend billions of dollars. There are a lot better ways to spend money that will do a lot more good for communities. Disaster preparation should mean: How do we use our resources most carefully and thoughtfully?
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