New Madrid Earthquake of 1812
In the past three centuries, major earthquakes outside of California and Alaska generally occurred in sparsely-settled areas, and damage and fatalities were largely minimal.
But some took place in areas that have since been heavily built up. Among them are three earthquakes that occurred in 1811 and 1812 near New Madrid, MO. They are among the Great earthquakes of known history, affecting the topography more than any other earthquake on the North American continent. Judging from their effects, they were of a magnitude of 8.0 or higher on the Richter Scale. They were felt over the entire United States outside of the Pacific coast. Large areas sank into the earth, new lakes were formed, the course of the Mississippi River was changed, and forests were destroyed over an area of 150,000 acres. Many houses at New Madrid were thrown down. "Houses, gardens, and fields were swallowed up" one source notes. But fatalities and damage were low, because the area was sparsely settled then.
This sequence of three very large earthquakes is usually referred to as the New Madrid earthquakes, after the Missouri town that was the largest settlement on the Mississippi River between St. Louis, Missouri and Natchez, Mississippi. On the basis of the large area of damage (600,000 square kilometers), the widespread area of perceptibility (5,000,000 square kilometers), and the complex physiographic changes that occurred, the New Madrid earthquakes of 1811-1812 rank as some of the largest in the United States since its settlement by Europeans. They were by far the largest east of the Rocky Mountains in the U.S. and Canada.
The 1811-1812 New Madrid Earthquakes (pronounced /njuː ˈmædrɪd/) were an intense intraplate earthquake series beginning with an initial pair of very large earthquakes on December 16, 1811. These earthquakes, as well as the seismic zone of their occurrence, were named for the Mississippi River town of New Madrid, Louisiana Territory, now Missouri.
There are estimates that the earthquakes were felt strongly over roughly 130,000 square kilometers (50,000 square miles), and moderately across nearly 3 million square kilometers (1 million square miles). The historic 1906 San Francisco earthquake, by comparison, was felt moderately over roughly 16,000 square kilometers (6,000 square miles).
In December of 1811, a the largest earthquake ever recorded in American History started. This earthquake, called the New Madrid Earthquake because of its primary location on the New Madrid Fault, near New Madrid, Missouri. From the effects of the 1811-1812 earthquakes, it can be estimated that they had a magnitude of 8.0 or higher on the not yet invented Richter scale. Large areas sank into the earth, new lakes were formed, and the Mississippi River changed its course due to the earthquakes.