The reassuring science behind middle-of-continent earthquakes

There’s little scientific evidence for this fear, according to Stein, the William Deering Professor of Earth and Planetary Sciences in the Weinberg College of Arts and Sciences at Northwestern.

Apocalyptic predictions of an earthquake in the New Madrid seismic zone persist. In 1990, a widely touted prediction said a big quake would hit the area, and a media circus ensued. The prediction proved false but highlighted the fear and hype surrounding the idea of a big Midwestern earthquake.

As the 200th anniversary of the big earthquakes that occurred in the area of New Madrid, Mo., approaches, talk of catastrophe is rising again.

“It’s said that the 1811 and 1812 earthquakes were the biggest in U.S. history, which isn’t true,” Stein said. “Or that they rang church bells in Boston, which isn’t true. And that another huge earthquake is on the way, which there’s no reason to believe.”

In the 1990s, Stein and other researchers conducted routine measurements of earthquake-related activity in New Madrid, with a high-tech version of the GPS technology used in cars and cell phones. Because big earthquakes had happened here about 500 years apart in the past, they expected to see the ground deforming as it stored up energy for another big earthquake. Instead, they found nothing.

The researchers were amazed. “We put markers in the ground and later measured their positions to an accuracy of a millimeter and found that the ground wasn't moving -- so there's no sign that a big earthquake is on the way,” he said. “Now we’ve got this whole new way of thinking about earthquakes in the middle of our continent.”

The findings detailed in “Disaster Deferred” (Columbia University Press, October 2010) come from more than 20 years of research about the New Madrid seismic zone. The book describes Stein’s scientific adventures that found no sign that big earthquakes will hit the New Madrid area in the next several hundred or even thousands of years.

Stein spoke with Erin White, broadcast editor at Northwestern, about the book.

Why was it important to write this book?

Widely circulated reports say a huge, disastrous earthquake is coming to the Midwest. You hear terrifying predictions about thousands of dead people, hundreds of billions of dollars of damage and other terrible stuff. These predictions are very vague about when the earthquake is coming but claim it’s soon enough that we have to start expensive preparations now to make buildings as strong as in California, where large earthquakes are much more common.

We, of course, can’t say there will never be another New Madrid earthquake like the ones in 1811 and 1812, but there’s no sign of one coming. The next could be thousands of years or tens of thousands of years in the future.

Talk about your surprise at the findings.

The most exciting surprise for a scientist is when a result comes out opposite what you expect. It shows that the way you'd been thinking has to be changed. It's like opening a door. In this case, it showed that the faults at New Madrid were acting very differently than we expected -- they switch on and off.

Now you have this whole new picture of earthquakes that you didn’t have before.

We now understand a lot more about earthquakes in the middle of continents. Continents have lots of faults spread over a huge area. For short times, some will be active and produce large earthquakes. Geologically, that’s a few thousand years. Then, they’ll be essentially dead -- producing at most small earthquakes -- for many thousands of years. Eventually, they or another fault will switch on. What we’ve learned is important for understanding the earthquake hazard in the Midwest but also for what it tells us about how earthquakes in continents work.

How do you explain the small earthquakes taking place in the Midwest?

Earthquake physics shows that many of those small earthquakes are aftershocks of the big earthquakes 200 years ago. They don’t show that a big one is coming.

What would you tell someone in the Midwest who's worried about earthquakes?

Enjoy the New Madrid bicentennial but don't worry too much about earthquakes. They're an interesting science question but not a serious danger. Make plans for your community carefully, using your experience that in the Midwest earthquakes aren’t a big problem. Decide between spending billions of dollars making buildings as strong as in California or using a less expensive standard and using the money for other needs. Consider whether more good would come from hiring teachers or putting lots of steel in schools that are very unlikely to be seriously shaken.

Why does “Disaster Deferred” focus on how ideas are changing?

When we try to interest young people in science careers, we shouldn’t present science as cut and dry, just facts. The book talks about the process of doing science and how we try to find out how the world works.

Why are some people disappointed when you say that a big earthquake isn’t on the way?

People like to be a little scared. We like Halloween, we like riding roller coasters, we like horror movies. We like the idea of danger, as long as it’s not too big.

That’s why we respond to the disaster stories that come along every few years. Remember, we had Y2K, and the world was going to end. And then we had swine flu, and the world was going to end. Then we were all supposed to go out and get duct tape and tape up our houses against biological terrorism.

These stories are “disaster chic,” as one news guy said. These disasters generally don’t happen, but they make a good story.

Provided by Northwestern University