Anniversary of the New Madrid Earthquakes

Prior to 2014, the most seismically active area in the U.S. was east of the Rocky Mountains in the Mississippi Valley area known as the New Madrid seismic zone. During the winter of 1811-1812, a series of earthquakes and after-shocks struck the mid-Mississippi River Valley on the banks of the Mississippi River, which was then the largest settlement town of New Madrid, now Missouri.

The three strongest earthquakes occurred on December 16, 1811, and January 23 and February 7, 1812. They registered estimated magnitudes of 8.6, 8.4, and 8.7, respectively on the Richter Scale. The earthquakes destroyed settlements along the Mississippi River, and caused damage and tremors that stretched across the northeastern United States and parts of Canada. Geologic studies show that the 1811-1812 sequence was preceded by at least two other similar sequences around the years 900 and 1450. Causes of New Madrid earthquakes are still being researched today.

• 1811, December 16, Northeast Arkansas
  This first main earthquake was felt over the entire eastern United States. The most frightening ground motions were felt in Nashville, Tennessee, and Louisville, Kentucky, where houses and other structures were severely shaken and chimneys knocked down.
• 1812, January 23, New Madrid, Missouri
  The second principal earthquake was the smallest of the three, but it was characterized by ground warping, carving of stream banks and severe landslides.
• 1812, February 7, New Madrid, Missouri
  The third principal earthquake was the largest. It destroyed the town of New Madrid.

Article Sources and Additional Resources

Summary of 1811-1812 New Madrid Earthquakes Sequence, - U.S. Geological Survey (USGS)

The New Madrid Seismic Zone (USGS)

Check out the USGS Computer Simulation of a Magnitude 7.7 Earthquake in the New Madrid Seismic Zone.

Watch the USGS video, "Effects and Accounts of the 1811-1812 New Madrid Earthquakes", February 8, 2011.

Find out about the National Park Services' (NPS) Concept III: New Madrid Earthquakes-Seismic Zone Tour Route. The goal for this concept would establish an auto tour route to illustrate the impact of the New Madrid earthquakes of 1811-1812, and to explore the implications of this active seismic zone for the lower Mississippi Delta region today.

Download the poster “20 Cool facts about the New Madrid Seismic Zone,” Commemorating the Bicentennial of the New Madrid Earthquake Sequence December 1811 – February 1812 (USGS). Some of these include:

• According to reports of boat captains and others on the Mississippi River in December 1811, the earthquakes caused the river to fill with debris as the tree-covered river banks caved into the river.
• As a result of land subsidence and uplift from the February 7, 1812, earthquake, water from the Mississippi River flooded the area and formed Reelfoot Lake. This event added to reports of the Mississippi River flowing backwards.
• It was reported that there is a 7–10% chance or probability that a quake of magnitude 7.0 or greater will occur in the New Madrid region within the next 50 years. The probability of a quake of magnitude 6.0 or greater occurring during the same time period is somewhere between 28 – 46%.
• The New Madrid Seismic Zone is the most seismically active area of the United States east of the Rocky Mountains, according to information from the last 40 years of instrumental recordings. It experiences an average of 200 earthquakes (greater than M1.5) every year— most, however, are too small to be felt.