The Midlands area is not known for earthquakes, but each year 10 to 30 earthquakes are recorded in South Carolina. With this in mind, schools, nursing homes, hospitals, county and municipal agencies and amateur radio operators have spent the week participating in earthquake drills.

The drills come during the state's annual earthquake awareness week.

The S.C. Emergency Management Division co-sponsors the awareness week with the College of Charleston, the S.C. Earthquake Education Program and the National Weather Service to remind the public that an earthquake could potentially be a serious threat to the county and state.

While the state records 10 to 30 earthquakes a year, only two to five of them are felt. These earthquakes tend to be less than a magnitude of 3.0 and cause little damage.

Most of the earthquakes in the state, 70 percent, occur in the Coastal Plain. Inside that Coastal Plain, most of the quakes are clustered around Ravenel-Adams, Run-Hollywood, Middleton Place and Summerville and Bowman.

Seismologists agree, where earthquakes have happened before, they can happen again.

The two most significant historical earthquakes in South Carolina were the 1886 Charleston earthquake and the 1913 Union County earthquake.

An Aug. 31, 1889 earthquake, which struck in the Summerville/ Charleston area, is the largest such event to have occurred in the southeastern U.S., and the most destructive, killing 60 people.

The 1913 Union County quake would measure about 5.5 on today's Richter scale based on the damage that was reported.

After Shock

Earthquakes have many effects that can be separated into two groups: primary and secondary.

Primary effects are always present in a severe earthquake. Those are: the ground shakes; roads buckle; buildings collapse; electric lines and gas mains can snap; large areas of ground can shift position; large bodies of water can rise and fall.

Aftershocks are earthquakes that follow the largest shock of an earthquake sequence. Aftershocks can continue over a period of weeks, months, or years. After the 1886 earthquake, 300 aftershocks were recorded in that area for a 2 1/2 year period.

In general, the larger the mainshock, the larger and more numerous the aftershocks, and the longer they will continue.

Secondary effects are other disasters caused by the earthquake's ground movement. Most of earthquake damage is done by secondary effects. Those effects are: landslides; soil liquefaction, when the movement forces water to seep into the material beneath a building. Saturated granular material loses its strength and briefly changes into a liquid from a solid, making foundations of structures very unstable; fires caused by gas and fuel leaks in pipes, cutting of electrical cables, etc. The destruction of water pipes makes it harder to fight such fires should they occur. The Earthquake of 1906 in San Francisco ruptured the main water supply, and as a result, there was extensive fire damage.

DAMAGE PREDICTIONS

Results of a scientific study commissioned by the S.C. Emergency Management Division indicate that an earthquake today of similar intensity (7.3) and location to the one in 1886 could have the following results: