Thursday, March 13, 2008

The New Madrid Fault

The New Madrid Fault is located in Southeast Missouri. The city of New Madrid sits on a major fault that extends into Arkansas. It crosses five states and covers over the Mississippi River in three places. Between December 1811 and February 1812, three major earthquakes occurred around New Madrid, Missouri. Theses earthquakes had a magnitude of 8.0 on the Richter scale. There was a series of 2,000 shocks in five months. Scientists believe this fault will produce more tremors in the future.
Today the fault is active. It averages more than 200 earthquakes a year. That is about 20 earthquakes per month. Tremors range from between 1-5 on the Richter scale. Every 18 months the fault reaches a magnitude of 4 or more. Earthquakes in this area of a magnitude of 5 or greater occur every decade. In 1996, an earthquake was felt in the states of Missouri, Arkansas, Tennessee, Kentucky, Illinois, and Mississippi. This earthquake had a magnitude of a 4.3.
Other than the West Coast, the New Madrid Fault has the highest earthquake risk in the United States. In this area, an earthquake of a 6.0 or greater happens every 80 years. There is a 90% chance of one occurring in 2040. The last one of this magnitude was in 1895. Major earthquakes of a 7.5 or greater in this area happen every 200-300 years. This means, that there is a 25% chance that one will occur again in 2040. An earthquake of this magnitude would be felt by half of the United States. It would also damage approximately twenty states.
Geologists have discovered data that ground near the fault moves a few milliliters each year. They also found evidence that sandy soil has liquefied. This suggests more potential for damage and for the tremors to be felt over a large area.
According to these finding, the new Madrid Fault is active. Earthquakes are occurring frequently. The magnitude and intensity of them varies. One thing is for sure, the soil and land of this seismic zone is changing and the probability of a great earthquake in the future is high.

No comments: