Public awareness of earthquakes in the United States is usually focused on California and Alaska where the Pacific Plate is slowly slipping underneath the North American Plate.
The most publicized earthquake zone is along the San Andreas Fault where San Francisco was struck with devastating earthquakes in 1989 and 1906.
People may not know about an earthquake zone east of the Rockies that made history in 1811 and where there may be a seismic event in the future.
New Madrid Seismic Zone
In the Central Mississippi Valley, there is an earthquake-prone area known as the New Madrid Seismic Zone. It starts in southern Illinois and angles southward through parts of Kentucky, Missouri, Tennessee and Arkansas. This area is also known as the New Madrid Fault Line or the Reelfoot Rift.
December 16, 1811 Earthquakes
The first tremor occurred at 2:15am with the epicenter in northeast Arkansas with a magnitude of 8.1. There was only slight damage to buildings because the area was sparsely populated. The earthquake triggered landslides and many changes to the land formation along the Mississippi River.
The second tremor occurred at 8:15am, again, centered in northeast Arkansas with a magnitude of 7.0. It intensified the damage caused by the quake six hours earlier. The opening and closing of fissures on the Earth’s surface spawned waves on the Mississippi River.
January 23, 1812 Earthquake
At 9:00am, a 7.8 magnitude earthquake struck and the epicenter was located in an area in southeastern Missouri known as the “bootheel”. There were numerous landslides, land fissures, warping ground and re-routing of rivers and streams.
February 7, 1812 Earthquake
The next earthquake struck at 4:45am with the epicenter near New Madrid, Missouri and a magnitude of 7.4. The town was destroyed. Effects were felt in St. Louis where many houses suffered damage. This triggered fissures, landslides and ground warping.
Damage Caused by the New Madrid Earthquakes
Witnesses reported the ground rolling in waves, the ground breaking open plus the sinking and rising of large tracts of land. In areas where the land sunk, water rushed in from ground fissures. Hillsides gave way and low land become ridges.
Along the Mississippi River, islands disappeared and the waves overturned boats or washed them to shore. River banks fell into the water. The course of the Mississippi permanently changed and land that was once on one side of the river, ended up on the opposite side of the riverbed.
There were claims that the New Madrid Earthquake caused the Mississippi River to flow backwards. In reality, the waves generated by the earthquake started to move upstream and it gave the illusion that the river had reversed its flow.
In swampy areas near the St Francis River, Arkansas, sand and coal spewed out of fissures. The river level rose by 24 feet.
There were reports of damage as far away as Washington DC, New York City and Cincinnati Ohio. Church bells rang in Boston which is over 1,000 miles away from New Madrid.
Predictions of Future Earthquakes in the New Madrid Fault Zone
According to the U.S. Geological Survey (USGS) in a report The Mississippi Valley – Whole Lotta Shakin’ Goin’ On:
“Scientists estimate that the probability of a magnitude 6 to 7 earthquake occurring in this seismic zone within the next 50 years is higher than 90%. Such an earthquake could hit the Mississippi Valley at any time. “
In 1983, the states of Tennessee, Missouri, Mississippi, Kentucky, Illinois and Indiana formed the Central United States Earthquake Consortium (CUSEC). Their mandate is to have disaster plans in place, improve seismic studies, educate the public and bring bridges, dams and buildings up to current earthquake standards.
Sources:
The Mississippi Valley – Whole Lotta Shakin’ Goin’ On: U.S. Geological Survey
New Madrid Earthquake: The Virtual Times
New Madrid Earthquakes 1811 - 1812: U.S. Geological Survey
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