Eastern Tennessee Seismic Zone
Alabama sits on the edge of the Eastern Tennessee seismic zone, which extends from south west Virginia to north east Alabama, is one of the most active earthquake areas in the Southeast.
Although the zone has not had a large earthquake in historic times, a few earthquakes have caused slight damage. The largest recorded earthquake in this seismic zone was a magnitude 4.6 that occurred in 1973 near Knoxville.
Sensitive seismographs have recorded hundreds of earthquakes too small to be felt in this seismic zone. Small, non-damaging, felt earthquakes occur about once a year.
Earthquakes in the central and eastern U.S., although less frequent, are typically felt over a much broader region than the western U.S. East of the Rockies, an earthquake can be felt in an area as much as ten times greater than a similar magnitude earthquake on the west coast.
For example, a magnitude 4.0 eastern U.S. earthquake typically can be felt at many locations as far as 100 km (60 mi) from where it occurred, and it might or might not cause damage near its source.
A magnitude 5.5 eastern US earthquake usually can be felt as far as 500 km (300 mi) in most directions and can cause damage out to 40 km (25 mi).
Source: U.S. Geological Survey