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The Earth and its heebie-jeebie shakes

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By Kirsten Peters

Not all Midwesterners realize they live in a region where earthquakes can strike, but they got a small reminder of that simple fact earlier this month when a 3.8 Richter scale temblor struck in northern Illinois. Let’s hope we can learn more from the event than just what the passing headlines might lead us to think about — because the center of our country is woefully under-prepared for much larger quakes yet to come.

That little Illinois temblor reminded me of the Big One that struck in the Midwest in the winter of 1811-1812. The quake was really four enormous events that occurred in and around what’s now Missouri over three months. Some of these mega-quakes were felt as far away as the East Coast where church bells rang! The Mississippi ran backward for a time due to the shaking and sloshing, and hamlets of the area were destroyed. The shape of the land itself was changed for many square miles, some of it rising upward, some sinking downward to become swamps. The big quakes were accompanied by hundreds of small ones, and local observers said that at one point the ground simply shook almost continuously for weeks.

The monstrous events are known as the New Madrid earthquakes — the name comes from a small town leveled during one of them. Modern geologists would say their epicenters were all part of the New Madrid Seismic Zone, which is an area that falls in the neighborhood of where Kentucky, Tennessee, Missouri and Arkansas all come together on the map. Since modern seismographs and the Richter scale itself had not been invented by 1811, there’s no way to say exactly how big the quakes were. But based on descriptions of the effects of the quakes, geologists estimate that the quakes were in the 7 to 8 range on the Richter scale — similar to or larger than what Haiti experienced earlier this winter.

(Just FYI, geologists expect areas near the epicenter of a Richter 8 quake to generally experience what is termed “total” damage. Because of the way the Richter scale works, a value of Richter 7 corresponds to a release of 31 times less energy than a Richter 8 quake, and is expected to result in mere “major” damage. And as another point of reference, of all the last century’s most deadly natural disasters the world around, about half were earthquakes — because even Richter 7s are deadly in the extreme if population is dense and buildings are made of bricks and blocks the old fashion way.)

One of the most staggering things about the New Madrid winter of 1811-1812 — staggering even to us geologists — is that there were multiple mega-quakes. Any one of the events would be a huge disaster today, affecting major cities, transportation and communication systems, small towns, rivers and levees. A full repeat of all that happened in New Madrid would be a greater disaster than anything we’ve ever seen out here along the west coast where this Rock Doc hangs her hat. Certainly the great quake in San Francisco in 1906 would pale in comparison.

A confounding factor about the New Madrid risk is that it has grown so much in the last century as population in the area grew. That’s one reason individuals in the Midwest — just like us westerners — should practice what they want their family members to do in the event of a major quake. And, in my opinion, stores of water and food are very much in order in the New Madrid Seismic Zone and the areas around it, just as they are along the Pacific Coast. The pictures on television from Haiti remind us of such facts.

We live on the outer crust of the Earth, and it’s a fragile eggshell. But you can do basic things to help yourself — and they can be useful whether you face an earthquake or, perhaps, another kind of emergency. Google “Red Cross emergency kit,” or make your own stores of basics, like this rock-head does.

Because another Big One is coming — you can count on that.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Follow her on the Web at rockdoc.wsu.edu and on Twitter @Roc

DocWSU. This column is a service of the College of Sciences at Washington State University.