It was 203 years ago Saturday that southeast Missouri experienced the third and final main shock from what turned out to be the most powerful series of earthquakes in the history of the United States.
The first, a 7.7 magnitude quake, took place around 2:15 a.m. in northeast Arkansas on Dec. 16, 1811. The second principal shock measuring slightly less than the first earthquake at 7.5 magnitude occurred in Missouri on Jan. 23, 1812, and the third a 7.7 magnitude like the first on Feb. 7, 1812, along the Reelfoot fault in Missouri and Tennessee.
It wasn’t just the main shocks that caused panic among the sparse populace of that time, but also the powerful aftershocks that followed. The first and largest of the aftershocks took place at around 7:15 a.m., just hours after the first earthquake on Dec. 16. Historical accounts indicate that at least three other large aftershocks took place between Dec. 16 and 17. These three aftershocks — located in Arkansas and Missouri are believed to have ranged from 6.0 and 6.5 in size.
This would make a total of seven earthquakes of magnitude 6.0-7.7 occurring from Dec. 16, 1811 through Feb. 7, 1812. A total of more than 200 moderate to large aftershocks were reported in the New Madrid region between Dec. 16, 1811, and March 15, 1812. Ten of these were greater than magnitude 6.0, about 100 were between 5.0 and 5.9 magnitude and 89 were in the magnitude 4 range. There were also about 1,800 earthquakes reported of between 3.0 and 4.0 magnitude during the same time period.
The following is a breakdown of each of the four major quakes, their effects and aftereffects:
— The First Main Shock • Dec. 16, 1811 • Northeast Arkansas • 2:15 a.m. • Magnitude 7.7
This powerful earthquake was felt widely over the entire eastern United States. People were awakened by the shaking in New York City, Washington, D.C., and Charleston, S.C. Perceptible ground shaking was in the range of one to three minutes depending upon the observer’s location. The ground motions were described as “most alarming and frightening” in places like Nashville, Tenn., and Louisville, Ky. Reports also describe houses and other structures being severely shaken, with many chimneys knocked down. In the epicentral area the ground surface was described as being in great convulsion, with sand and water ejected tens of feet into the air — a process called liquefaction.
— The “Dawn” Aftershock • Dec. 16, 1811 • Northeast Arkansas • 7:15 a.m. • Magnitude 7.0
A large event felt on the East Coast that is sometimes regarded as the fourth principal earthquake of the 1811-1812 sequence. The event was described as “severe” at New Bourbon, Mo. Boatman John Bradbury, who was moored to a small island south of New Madrid, said the aftershock was as “terrible, but not equal to the first.” It’s believed the large aftershock occurred around dawn in the New Madrid region, near the surface projection of the Reelfoot fault.
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— The Second Main Shock • Jan. 23, 1812 • New Madrid, Mo. • 9:15 a.m. • Magnitude 7.5
It is difficult to assign intensities to the principal shocks that occurred after 1811, because many of the published accounts describe the cumulative effects of all the earthquakes. Also, because the Ohio River was iced over, there was little river traffic and fewer human observers. Using the Dec. 16 earthquake as a standard; however, there is a general consensus that this earthquake was the smallest of the three main shocks. The meizoseismal area was characterized by general ground warping, ejections, fissuring, severe landslides and caving of stream banks.
— The Third Main Shock • Feb. 7, 1812 • New Madrid, Mo. • 3:45 a.m. • Magnitude 7.7
Several destructive shocks occurred on Feb. 7, the last of which equaled or surpassed the magnitude of any of the previous quakes. It totally destroyed the town of New Madrid. At St. Louis, many houses were damaged severely and their chimneys thrown down. The meizoseismal area was characterized by general ground warping, ejections, fissuring, severe landslides and caving of stream banks.
So, how likely is this region to have a repeat of the New Madrid quakes? Some experts say that, after the passing of more than 200 years, southeast Missouri is overdue for another hit and that it could be devastating — particularly to the city of Memphis, Tennessee. But then there is Seth Stein, a seismologist at Northwestern University and author of the book, “Disaster Deferred: How New Science is Changing Our View of Earthquake Hazards in the Midwest.”
Stein says that GPS studies of ground movements in the region suggest that the current hazard for another major earthquake is quite low. This has put him in direct opposition to those who caution that people living in the New Madrid region should prepare for future hazards. Citing the potential dangers of future earthquakes, government agencies — including the Federal Emergency Management Agency (FEMA) and the U.S. Geological Survey (USGS) — have urged the region to adopt stricter building codes. Stein disagrees, saying regulations like these would cost communities billions and be unnecessary, as well. He believes New Madrid’s Reelfoot Fault is dying.
"It’s unlikely to do anything on a timescale of thousands of years," he said. "The history of these kinds of faults is that they are active for a few thousand years, then dormant, then active again."