Alabama and the Great Central U.S. ShakeOut
Earthquakes in Alabama
The term earthquake brings to mind impressive news stories from far off places such as California, Iran, or Alaska. However, less spectacular earthquakes are fairly common in the eastern half of the United States and are not uncommon in Alabama. Three zones of frequent earthquake activity affecting Alabama are the New Madrid Seismic Zone (NMSZ), the Southern Appalachian Seismic Zone (SASZ) (also called the Eastern Tennessee Seismic Zone), and the South Carolina Seismic Zone (SCSZ).
The New Madrid Seismic Zone lies within the central Mississippi Valley, extending from northeast Arkansas through southeast Missouri, western Tennessee, and western Kentucky, to southern Illinois. Historically, this area has been the site of some of the largest earthquakes in North America. The last major earthquakes in this area were in 1811 and 1812, when population was small and there were few buildings. Today the area is densely populated by millions of people and includes the cities of St. Louis, Missouri, and Memphis, Tennessee. A major earthquake could result in great loss of life and property damage in the billions of dollars. Adding to the danger is the fact that structures in the area were not built to withstand earthquake shaking. There is a 90% chance of an earthquake of magnitude 6.0 or greater in this area by the year 2040. A large earthquake could result in significant damage in northern Alabama and would have a significant economic impact on Alabama.
The Southern Appalachian Seismic Zone extends from near Roanoke in southwestern Virginia southwestward to central Alabama. Considered a zone of moderate risk, the SASZ includes the Appalachian Mountains. The hypocenters of earthquakes in this zone are probably on deeply buried faults. The greatest earthquake in the zone occurred in 1897 near Pearisburg, Virginia, with an estimated magnitude of 5.8. Most of the earthquakes in Alabama are in the SASZ.
On August 13, 1886, the southeastern United States was strongly shaken by a large magnitude 7.3 earthquake centered at Charleston, South Carolina, in what is known as the South Carolina Seismic Zone. The earthquake leveled almost every building in the Charleston area and caused 60 deaths. The earthquake was felt 750 miles from the epicenter, and several areas in Alabama recorded damage.