Earthquakes in the Lower Mississippi Valley


Over two centuries ago, during the winter of 1811-1812 a series of earthquakes occurred in what was then the country’s western frontier. A great earthquake on December 16, 1811, marked the beginning of a set of earthquakes that occurred in northeast Arkansas and southern Missouri. The largest earthquakes were felt from Canada to New Orleans to the Atlantic coast.

Earthquakes and aftershocks are estimated to have lasted two years. With no seismic stations in 1811, the exact number of earth­quakes that occurred because of the New Madrid event remains unknown. The most noted dam­age was to the small settlement of New Madrid, situated along the banks of the Mississippi River in southern Missouri. As a result of the earthquake and erosion of the river shortly thereafter, the town literally slid, piece by piece, into the Mississippi River and was washed downstream. The pres­ent town of New Madrid is lo­cated near the original site, but behind a levee. Today, this zone is referred to as the New Madrid Seismic Zone in honor of this small frontier town.

Eyewitness accounts of the events were collected years after­ward by several authors. The de­scriptions of the events are impressive. There were few set­tlers in the area, so damage to structures was low, but destruc­tion of the local forests was ex­tensive. The accounts describe surface waves that moved along the ground surface like ripples on water when a pebble is thrown into a pond. These ground waves moved through the countryside and caused damage to the wood­lands as trees “rode over” the top of the wave. There was ex­tensive caving of banks along the Mississippi River and on steep slopes away from the river. When these slopes failed, a mass of mixed trees and soil came to rest at the base of the slope. Islands in the Mississippi River disap­peared as far south as Island 94 near Vicksburg, Mississippi. Per­haps the largest factor affecting the woodlands was abrupt changes in the elevation of the land surface. Extensive areas ex­tending from Arkansas northward into Missouri are often referred to as the “sunken lands.” In much of this area the land surface sunk as much as 20 feet, turning upland forests into swamps. The abrupt change from dry uplands to water-saturated swamp environ­ments caused an extensive die-off of upland species of trees.

The New Madrid faults are still active and capable of generating damaging earthquakes. The Mis­sissippi Emergency Management Agency has estimated potential magnitude 8 earthquake in the New Madrid Seismic Zone, would be more than $3 billion. A study at the University of Mississippi suggested a similar earthquake scenario could result in more than $112 million of damage just at the main campus.

Contact your local emergency manager and find out what they are doing on a local level to in­form government and private cit­izens about earthquake preparedness. They can also ad­vise you on what to keep on hand in the event we should ever have an earthquake.

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