South Carolina EARTHQUAKE HAZARDS

While South Carolina is usually not known for earthquakes, ten to thirty earthquakes are recorded annually and two to five earthquakes are felt each year. These earthquakes tend to be less than magnitude 3.0 on the magnitude scale and cause little damage.

Most of South Carolina’s earthquakes occur in the Coastal Plain where the underlying rocks are very faulted or broken from the break-up of the plates. These cracks in the deep rocks mean that this area of the plate is weak. If pressure is exerted on the edge of the plate, some of these faults/breaks will allow the rocks to move. Faults in South Carolina have been mapped and estimated. Fault rupture is not the only cause of earthquakes. Small earthquakes may also occur near dams from water pressure and near the Appalachian Mountains.

Currently, there is no reliable method for predicting the time, place, and size of an earthquake. Several areas of South Carolina regularly experience earthquakes and have experienced strong earthquakes in the past. Approximately 70% of all earthquakes in the state occur in the Coastal Plain with most clustered around three areas of the State: Ravenel-Adams Run-Hollywood, Middleton-Place-Summerville, and Bowman. There is a consensus among seismologists that where earthquakes have occurred before, they can again.

On August 31, 1886 Charleston, South Carolina, experienced the most damaging earthquake in the eastern United States. The initial shock lasted nearly one minute. The earthquake had a magnitude of 7.3 (Johnson, 1996) and was felt over 2.5 million square miles, from Cuba to New York, and Bermuda to the Mississippi River. Structural damage extended several hundred miles to cities in Alabama, Ohio, and Kentucky. At the time of the earthquake, many of the residents of Charleston thought it was a calamity that struck the entire world. Many residents were surprised when they discovered it was principally their area where the majority of severe damage occurred.

Geologically, Charleston lies in one of the most seismically active areas in the Eastern United States. The seismicity in the Coastal Plain of South Carolina clusters around the cities of Summerville and Bowman, SC, known as the Middleton Place - Summerville Seismic Zone (MPSSZ).

Currently the MPSSZ experiences between 10 to 15 magnitude 3 or less events every year. Large events, like the 1886 earthquake, have been recorded in the oral history of the area (~1600 and 13-1400's AD). Additionally, paleoseismic investigations have shown evidence for several pre-historic, liquefaction-inducing earthquakes in coastal South Carolina in the last 6000 years. If the present is the key to the past, and the past is an analog for the future, then the Charleston region can expect to experience another 1886 magnitude event in the future.

Information Source South Carolina Emergency Management Division Earthquake guide:
https://www.scemd.org/stay-informed/publications/earthquake-guide/

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Please visit the following links for more information:

South Carolina Emergency Management Division
https://www.scemd.org/prepare/types-of-disasters/earthquakes/

SCEMD Earthquake Page:
https://www.scemd.org/prepare/types-of-disasters/earthquakes/

SC Earthquake Education and Preparedness Program (SCEEP)
http://scearthquakes.cofc.edu

SC Seismic Network
http://www.seis.sc.edu/projects/SCSN

State Geological Survey Website
http://www.dnr.sc.gov/geology

USGS South Carolina Earthquake Webpage
http://earthquake.usgs.gov/earthquakes/byregion/southcarolina.php