The following is an interview with Seth Stein, author of Disaster Deferred: How New Science is Changing Our View of Earthquake Hazards in the Midwest.
Q: What’s wrong with the stories we hear about the 1811 and 1812 New Madrid earthquakes?
Seth Stein: A lot of what you hear is hype. For example, you hear that these were the biggest earthquakes that ever hit the U.S. In fact there are about 15 earthquakes of the same magnitude somewhere in the world every year. Similarly, the story that they rang church bells in Boston isn’t true. Actually, there’s no record that anyone in Boston felt them. There’s also the story that the Indian chief Tecumseh predicted them. Actually, after the earthquakes he told his followers that they proved that the Great Spirit was on the Indians’ side.
Q: The government says that earthquakes will again happen in the Midwest and cause a huge natural disaster unless we start preparing now. Why do you disagree?
S.S.: Twenty years ago every geologist thought that. We knew there had been big earthquakes in 1811 and 1812, and geological studies showed that there had been earthquakes in about 1450 and 900 AD. So it looked like earthquakes happen about every 500 years. We couldn’t test that idea until about 1990, when the Global Positioning System–GPS–came along. That let us put markers in the ground and measure the position of the Midwestern fault lines using a fancier version of the GPS systems used in cars and cell phones. Geologists started making measurements near faults all around the world where there was a history of earthquakes. They discovered you could measure the ground moving as it stored up energy for a future earthquake. To our surprise, measurements at the New Madrid earthquake zone showed that the ground wasn’t moving. We concluded there is no sign that a big Midwestern earthquake is on the way.
Q: Don’t the small earthquakes happening in the Midwest today prove that a huge one is coming? S.S.: Our results show that most of those small earthquakes are aftershocks of the big earthquakes from 200 years ago. It makes sense because they happen on the faults we think moved 200 years ago.
Q: How can it be that the New Madrid fault is no longer active?
S.S.: The idea that faults can turn on and off seems surprising, but it’s catching on quickly for a couple of reasons.
First, it explains a lot of the puzzles about New Madrid. We know that the faults at New Madrid are hundreds of millions of years old, but throughout their history they haven’t moved most of the time. If faults move a lot they make topography like mountains, and the Midwest is some of the flattest land in the country. It didn’t square with what we see.
Second, once geologists started looking, we realized that faults within other continents–China, Europe, and Australia–also switch on and off.
Q: Knowing this, how can the government claim that the Midwest is in as much earthquake danger as California?
S.S.: That conclusion made sense with what we knew 20 years ago, but we know so much more now. Now it looks like the danger of earthquakes in the Midwest is about 1/10th that of California’s. Of course, we’ll keep studying the area, but from what we know there is no point rushing into expensive California-level preparations. More modest preparations would cost less and let resources be used other ways that do more good.
Q: Even if the risk is much less than the government says, doesn’t it make sense to prepare
S.S.: Remember President Reagan’s line that the scariest phrase in the English language is “we’re from the government and we’re here to help.” The problem is that the preparations the government wants communities and business to take are very expensive. Bringing one hospital in Memphis up to California standards cost about 100 million dollars. Bringing all the buildings in the area up to this standard would take billions of dollars. Spending that money on other social needs would do a lot more good. Similarly, requiring businesses to spend money this way is a huge tax with little benefit. It’s likely that many buildings in California will be seriously shaken by an earthquake during their lives, while a building in the Midwest is very unlikely to be.
Q: So, what’s your overall advice about Midwest earthquakes?
S.S.: We should keep learning more about them, but don’t need to rush into expensive precautions. The government is pushing communities to spend money that can be better utilized elsewhere for greater social good. As the old joke goes, “do you want it right or do you want it now?”
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