New Madrid awakening?

| April 18, 2008

One of the most powerful earthquakes known of in continental North America since European settlement was the New Madrid earthquake in 1811. Damage occurred over an area of nearly 240,000 mi2, and the quake itself was felt over an area of nearly 2 million mi2. Here’s a partial description of the impact:

At the onset of the earthquake the ground rose and fell – bending the trees until their branches intertwined and opening deep cracks in the ground. Landslides swept down the steeper bluffs and hillslides; large areas of land were uplifted; and still larger areas sank and were covered with water that emerged through fissures or craterlets. Huge waves on the Mississippi River overwhelmed many boats and washed others high on the shore. High banks caved and collapsed into the river; sand bars and points of islands gave way; whole islands disappeared. Surface rupturing did not occur, however. The region most seriously affected was characterized by raised or sunken lands, fissures, sinks, sand blows, and large landslides that covered an area of 78,000 – 129,000 square kilometers, extending from Cairo, Illinois, to Memphis, Tennessee, and from Crowleys Ridge to Chickasaw Bluffs, Tennessee.

Although the motion during the first shock was violent at New Madrid, Missouri, it was not as heavy and destructive as that caused by two aftershocks about 6 hours later. Only one life was lost in falling buildings at New Madrid, but chimneys were toppled and log cabins were thrown down as far distant as Cincinnati, Ohio; St. Louis, Missouri; and in many places in Kentucky, Missouri, and Tennessee.

The map above shows the estimated epicenter of the 1811 New Madrid quake. The Midwest is not an area we tend to associate with major earthquakes — we tend to think of the Pacific Rim (California, Oregon, Washington, Alaska) instead. And the truth is, things have been pretty quiet in the Midwest since the New Madrid quake.

However, a 5.2 earthquake hit Illlinois this morning and was felt over a wide area. Here’s the epicenter [NOTE: the map is updating itself; it now appears there have been several aftershocks, including one at magnitude 4.5; click on the map below to go to the USGS web site]:

Not an area where you want to see increased seismic activity. Hopefully this is just a stress-reliever for the New Madrid fault system and not a harbinger of quakes to come. ..bruce w..

[Henderson – Update]

As fate would have it, I am in Central Illinois at the moment, and the quake is the subject of quite a bit of conversation here. Most folks in the rural area around Bloomington Illinois did not feel the quake, but it did crack the ceiling at my mother’s house.

What is interesting about the location is it is outside the normal New Madrid activity area, and I am sure it will cause scientist to reconsider the geometry of the midwest fault system.

Most of the people in this part of the US are vaguely familiar with the fact that there is an active seismic zone under foot, but they do not take it seriously.

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Category: Earthquakes, Emergency Preparedness, Main, Maps

About the Author ()

Webster is Principal and Founder at Bruce F. Webster & Associates, as well as an Adjunct Professor of Computer Science at Brigham Young University. He works with organizations to help them with troubled or failed information technology (IT) projects. He has also worked in several dozen legal cases as a consultant and as a testifying expert, both in the United States and Japan. He can be reached at bwebster@bfwa.com, or you can follow him on Twitter as @bfwebster.

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