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The New Madrid Fault is located beneath the Mississippi River Valley in the Midwest United States. It is part of the North American tectonic plate and the major fault among four, located in this region. It is yet to be confirmed if these faults intersect or are unique to each other.
Faults result from cracks and breaks in rock formations. These faults increase the seismic activity and cause periodic earthquake events. Until the beginning of the 21st Century, the New Madrid Fault received little scientific attention. There is little information available on this or any of the faults comprising this seismic zone, which involve Illinois, Missouri, Arkansas, Tennessee and Kentucky.
It is difficult to decipher the New Madrid Fault because its behavior is unique when compared to other sites around the world. It is also a significant distance from competing tectonic plates which have previously been considered a major cause of seismic activity.
New Madrid Fault's greatest activity is located 3 to 15 miles (5 to 25 km) beneath the surface of the earth. The activity is unique in that earthquakes are felt hundreds and sometimes thousands of miles away from the epicenter, and are consequently far more damaging. The reason such a wide range is affected is that the hundreds of miles of bedrock beneath much of central and eastern United States is very rigid and far less fractured. This stronger, more continuous soil does not absorb the waves. As a result, this allows the waves to travel farther. A comparable size earthquake would do considerably more damage if located on the New Madrid Fault vs. the San Andreas Fault.
The New Madrid Fault is most noted for the 1812 earthquake, which is the strongest earthquake ever recorded in modern times in the continental United States. It is estimated to have measured 8.0 on the Richter scale. It was preceded by three earthquakes, having magnitudes greater than 7.0. All four of these earthquakes took place within a three-month period between 1811 and 1812. The strongest of these events was felt as far away as New England. The intensity of that quake caused the Mississippi River to run backward for three days, creating permanent lakes and course changes in the river itself. While new lakes formed, such as Reelfront Lake, other lakes were permanently drained.
Some estimations put the New Madrid Fault in jeopardy of strong, damaging earthquakes, measuring over 7.0 magnitude every 300 to 500 years. Other research suggests a far shorter time frame. It is estimated that there are about 150 quakes per year in this region. Over 4,000 earthquakes have been identified since 1974.
Scientific opinion varies as to future activity of the New Madrid Fault. Most seem to agree that there is a 90% chance of an earthquake ranging between 6.0 and 8.0 magnitude by the year 2040. Building codes and earthquake insurance protection have significantly gained importance for all of the Midwest.