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(For the week of February 8, 2010)
by James L. Cummins
The earthquake that rocked Haiti last month is an absolute tragedy. But our part of the planet can be unstable too.
We don't have to go too far back in time to find out that on December 16, 1811, a huge earthquake marked the introduction of a set of earthquakes that occurred in Northeast Arkansas and Southern Missouri. The largest earthquakes were felt from Canada to New Orleans and eastward toward the Atlantic coast. Earthquakes and aftershocks are estimated to have lasted 2 years. Since there were no seismic stations at that time, the exact number of earthquakes that occurred as a result remains unidentified. The most prominent damage was to the small settlement of New Madrid which was situated along the banks of the Mississippi River in Southern Missouri. As a result of the earthquake and erosion of the river, the town literally slid into the Mississippi River and was washed away. The present town of New Madrid was rebuilt near the original site, but is now situated behind a levee.
The area was sparsely populated, so damage to structures was low, but the local forest damages were extensive. There were surface waves that moved along the ground surface. These ground waves caused damage to the woodlands as trees “rode over” the top of the wave. There were widespread cave-ins of banks along the Mississippi River and on steep slopes away from the river. When these slopes crashed, a mass of trees and soil came to rest at the base. The trees usually died and if they came to rest in or next to the river, they were carried away with the flow of the water. The largest factor affecting the forests was immediate changes in the elevation of the land surface. Massive areas extending from Arkansas into Missouri are often referred to as the “sunken lands.” In much of this area, the land surface sunk as much as 20 feet. The few accounts of wildlife's reaction to the earthquakes were pretty much the same as the reaction of the people in the affected areas – confused and terrified.
The New Madrid fault is still active and capable of generating damaging earthquakes today. Since earthquakes give no warning and prediction is difficult at best, preparedness is important. Don't forget earthquakes are a very real hazard.
Take time to learn about earthquakes and identify ways you could make your surroundings more earthquake resistant.
You can see where earthquakes are occurring throughout the world at http://earthquake.usgs.gov/earthquakes/index.php. The Center for Earthquake Research and Information has a useful website at www.ceri.memphis.edu/.
Don't over react; just be knowledgeable and prepared.