New Madrid Earthquakes Of 1811–1812

New Madrid earthquakes of 1811–12, series of three large earthquakes that occurred near New Madrid, Missouri, between December 1811 and February 1812. There were thousands of aftershocks, of which 1,874 were large enough to be felt in Louisville, Kentucky, about 190 miles (300 km) away. The number of lives lost from the earthquakes remains unknown; however, scholars note that the number was probably not great, because the region had only a sparse rural population.

The earthquakes and their aftershocks took place within a large region called the New Madrid Seismic Zone (NMSZ)—an area of high earthquake risk running from northeastern Arkansas and northwestern Tennessee to southeastern Missouri and southwestern Kentucky. Magnitude estimates for each of the three events associated with the 1811–12 earthquake sequence vary widely, largely because they rely on historical accounts and analyses of the present-day landscape rather than data provided by modern seismic instrumentation. The magnitude of the December 16, 1811, event ranged from 6.7 to 8.1, whereas the ranges for the earthquakes of January 23 and February 7, 1812, were 6.8–7.8 and 7.0–8.8, respectively. More-precise figures have been presented by the United States Geological Survey (USGS) Earthquake Hazards Program: magnitude 7.7 for the December earthquake and magnitudes 7.5 and 7.7 for the January and February earthquakes, respectively. Scholars do agree, however, that the New Madrid earthquakes were the strongest such events recorded in North America east of the Rocky Mountains.