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Friday, July 25, 2014

Midwest has rocked and rolled

Tuesday, March 15, 2011

Most of us have been riveted by the scenes of destruction caused by the Japanese earthquake and subsequent tsunami. Thousands are confirmed dead, with thousands more missing.

Our hearts go out to the people of Japan. While they begin the heartbreaking process of cleaning up, amidst countless aftershocks, they warily look to the north of their country, at nuclear power plants on the edge of meltdowns.

Japan is among the most prepared nations in the world when it comes to earthquakes. Living, as they do, in the "ring of fire" in the Pacific, earthquakes are a way of life. But, they've learned that Mother Nature doesn't take preparedness into consideration when she unleashes her wrath.

What about us? Are you prepared for an earthquake?

I know, I know, we live in Iowa. We're not exactly in the middle of earthquake alley.

Or are we?

This marks the bicentennial year of the Great New Madrid earthquake of 1811-1812. With a magnitude of between 7.5 and 8.0 on today's Richter scale, it remains by far the strongest earthquake ever recorded east of the Rocky Mountains.

New Madrid, Missouri, the epicenter of that quake, lies in far southeastern Missouri. At the time, it was the largest settlement on the Missouri between St. Louis and Natchez, Mississippi. After the initial earthquake on Dec. 16, 1811, several more, large, aftershocks continued for over a month. The largest of them, on February 7, 1812, surpassed the magnitude of any of the previous shocks. It destroyed the town of New Madrid, and damaged homes in St. Louis. Stories were told of church bells ringing in Boston, Mass., and sidewalks cracked in Washington, D.C., as shock waves were felt that far away.

So, what does that earthquake have to do with us?

Well, the New Madrid Seismic Zone is active to this day. It's made up of faults that formed when what is now North America began to split during the breakup of the super-continent Rodinia about 750 million years ago. The ancient faults appear to have made the rocks deep in the earth's crust in the New Madrid area weaker than much of the rest of North America.

That weakness, combined with the pressure from stronger rocks nearby, allows the small east-west compressive forces that exist in the North American plate to reactivate old faults, make the area prone to earthquakes.

While the shakes are not large, the area continues to be active. Small temblor occur in the region, and experts give a 7-10 percent chance, in the next 50 years, of a repeat of a major earthquake like that in 1811-1812. There's a 25-40 percent chance of a magnitude 6.0 or greater quake in the next 50 years.

The U.S. Emergency Management Agency says such a quake would result in "widespread and catastrophic" damage across Alabama, Arkansas, Illinois, Indiana, Kentucky, Missouri and particularly Tennessee.

While here in northwest Iowa, we would be spared from most damage, it strikes a bit too close to home for this Midwesterner. And, it probably seems pretty inconceivable to most other Midwesterners.

Which is why it's so dangerous.


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Paula Buenger
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