New Madrid Earthquake Sequence Dec 1811–Feb 1812

The page and posters summarize a few of the more significant facts about the series of large earthquakes that struck the New Madrid seismic zone of southeastern Missouri, northeastern Arkansas, and adjacent parts of Tennessee and Kentucky from December 1811 to February 1812. Three earthquakes in this sequence had a magnitude (M) of 7.0 or greater. The first earthquake occurred on December 16, 1811, at 2:15 a.m.; the second on January 23, 1812, at 9 a.m.; and the third on February 7, 1812, at 3:45 a.m. These three earthquakes were among the largest to strike North America since European settlement. The mainshocks were followed by many hundreds of aftershocks that occurred over the next decade. Many of the aftershocks were major earthquakes themselves. The area that was strongly shaken by the three main shocks was 2–3 times as large as the strongly shaken area of the 1964 M9.2 Alaskan earthquake and 10 times as large as that of the 1906 M7.8 San Francisco earthquake. Geologic studies show that the 1811–1812 sequence was not an isolated event in the New Madrid region. The 1811–1812 New Madrid earthquake sequence was preceded by at least two other similar sequences in about A.D. 1450 and A.D. 900. Research also indicates that other large earthquakes have occurred in the region surrounding the main New Madrid seismicity trends in the past 5,000 years or so.

1. First Mainshock Earthquake
The first in a series of major earthquakes occurred on December 16, 1811, at about 2:15 a.m. near present-day Blytheville, Arkansas. Estimated at magnitude (M) 7.7 (footnote 1), this event awakened people across much of what is now the eastern United States, up to about 900 miles away, including President James Madison in Washington, D.C. There were several large aftershocks that day, including the largest “Dawn” aftershock at about 7:15 a.m., estimated at M6.8–7.0.

4. Second Mainshock Earthquake
The second of the three major earthquakes, estimated at M7.5, occurred on January 23, 1812, at about 9:15 a.m. Similar to the December 1811 earthquake, this event was also widely felt throughout the region. Damage occurred in an area of about 232,000 square miles.

7. Third Mainshock Earthquake
The third and probably the most widely felt of the three major New Madrid earthquakes occurred on February 7, 1812, at about 3:00 a.m. There were several destructive shocks that day, the last and largest estimated at M7.7. As a result, the town of New Madrid, Missouri, was severely damaged.

Big SNIP :)


The middle of the US has been considered stable, so strong earthquakes are rather surprising.
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It will be interesting to see what follows the recent earthquakes in Va and Ok.