New Madrid earthquake of 1811

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The New Madrid Seismic Zone and the Wabash Valley Seismic Zone.

On December 16, 1811, January 23, 1812 and February 7, 1812 three earthquakes occurred , the epicentres of which were around New Madrid and each of which had a magnitude of 7. The earthquakes changed the course of the Mississippi River , caused the Ohio River to flow backwards at times, created new lakes such as Reelfoot Lake in Tennessee, and led to major geological changes between St. Louis and Memphis (Tennessee) . The tremors were so strong that the bells began to ring on their own in the city of Boston , Massachusetts, 1,600 miles away .

The earthquakes were therefore not limited to the area around New Madrid. The primary zone of origin of the earthquakes, "New Madrid Seismic Zone (NMSZ)", is still active. In 1974 several measuring stations were built around this area and have been able to measure over 4000 smaller earthquakes to date. Scientists suspect that there is a 50 percent probability that there will be an earthquake with a magnitude of 8 on the Richter scale by 2050 , the epicenter of which is in the NMSZ.

1811, 1812

New Madrid Seismic Zone : active earthquake zone

In 1811 and 1812 the strongest earthquakes occurred in this region since the Europeans first colonized the area. Some people have written eyewitness reports on this particular natural phenomenon. A report from a resident in New Madrid read:

“At two o'clock on December 16, 1811, we were awakened by the violent shaking of an earthquake. Accompanied by a terribly loud noise, similar to a distant thunder, only rougher and more vibrating. After a few minutes, the atmosphere was completely saturated with sulphate-filled vapor, which resulted in complete darkness. All the people were screaming and running around without knowing where to go or what to do. You could also hear the crack of the falling trees and the roar of the Mississippi, which even ran backwards for a short time. All of this made a really terrible scene. So in the further course of the morning there were a few smaller earthquakes, and when the sun rose, another bigger one, maybe even stronger than the first one. In one specific case, a woman was so panicked that she passed out and never woke up. After that there were always earthquakes, but they were a lot weaker. Until on January 23rd another earthquake as strong as the first one happened. From then on, until February 4th, the earth was in constant motion. It looked like the bottom was slowly undulating like a calm sea. On February 7th, another severe tremor occurred which was much stronger than the previous ones. The loud thunder and darkness that accompanied the earthquake created a picture that requires a hard-to-imagine imagination to describe. So the waters of the Mississippi receded from the banks like a great mountain and left the boats for a short time on bare sand. Then the water masses grew up to five meters and spread, and at the same time they flooded the banks as fast as a storm. The boats that had previously been left on the sand were now torn from the fortifications and drifting away in a tributary where they were washed up to a mile further. Many large fish were washed up on the sandbanks, unable to follow the speed of the water. The river was now polluted, including with destroyed boats. The earth was torn apart in many parts and there were often deep crevices. The location of the village shifted by at least 4 meters. No change in the course of the river was noticeable further down, but many small ponds and lakes formed upstream. Most of them dried up after a short time. Many of these lakes caused the river bank to shift by 3, 4 or even 6 meters. Recently even a lake was discovered in the Indian country, which is a hundred miles long and in some places 50 meters deep ... "

Reelfoot Rift - earthquake origin zone

Reelfoot Rift : still active rift zone
4000 earthquake measurements since 1974

The “Reelfoot Rift” goes back to around 750 million years ago when the entire land mass of the earth formed a single supercontinent , Rodinia . At that time, a constructive rift zone began to form in North America , the “Reelfoot Rift”, but this failed and the zone became inactive. Around 550 million years later, at the time of the supercontinent Pangea , the rift zone became active again, but no longer acted as a constructive plate and has remained in roughly the same state to this day. The earthquakes are therefore due to seismic activity 5 to 25 km below the earth's surface .

New Madrid seismic zone (NMSZ)

Earthquake measurements since 1974 have allowed over 4,000 earthquakes to be assigned to the respective zones of origin, which results in a picture as shown on the map on the right. It can be seen that the earthquakes can be traced back to the seismic activities of the “Reelfoot Rift”. The zone that is colored solid red in the picture is called the "New Madrid Seismic Zone".

today

The zone is still active today. There have been minor earthquakes for several decades. Scientists assume that there will be an earthquake with a magnitude greater than 7 (Richter scale) in the next 50 years with a probability of over 90%. Such a quake was described in the science fiction novel Magnitude 10 (Judge 10) by Arthur C. Clarke and Mike McQuay .

Today the situation is more precarious than it was 200 years ago. The area is now more densely populated, and some of the buildings are not earthquake-proof . Some states have joined forces and founded an institute especially for their earthquake zone in order to be as well prepared as possible for the great earthquake, or as they call it: The Next Big One . The Mississippi is likely to be one of the most unpredictable problems. Some donation accounts have already been set up for earthquake victims. Measures have also been taken to curb the natural disasters that follow an earthquake ; When building dams, bridges and highways, special attention was paid to earthquake security.

In contrast to the San Andreas Trench , understanding of this earthquake zone is only gradually increasing, and it must be assumed that there is a permanent earthquake hazard that affects both the east and the Midwest of the USA.

More pictures

  • Comparison of the spread of a later, somewhat weaker (magnitude 6.8) earthquake (1895) in the same area with the 1994 earthquake in California

  • Contemporary drawing

  • Reelfoot Rift and NMSZ

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