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EARTHQUAKES
AND ALABAMA
SEISMIC ZONES AFFECTING 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.
Charleston, South Carolina, earthquake of
1886
Source: U.S. Geological Survey
To obtain information on the current and historical seismicity of
the eastern and central United States, check the links below.
Near-real time Source for Earthquake Activity in the Central & Eastern
United States
Historical Seismicity Map for the Eastern United States
Current Seismicity Map for the Central United States
Historical Seismicity Map for the Central United States

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