How to prepare for an earthquake
Luckily for South Carolinians, the Palmetto State isn't, by any stretch, known as a hotbed of earthquake activity.
So it's a somewhat curious statistic that the area surrounding the small town of Pageland, just south of the North Carolina border, has registered three earthquakes — albeit, small ones — in the past six months, and four in the past year.
The rumbles came at night or in the early morning hours, when most people were sleeping or just beginning their days, meaning the slight shakes went almost entirely unnoticed.
The most recent, a 1.9 magnitude quake, was recorded April 5 just before 10 p.m. Another, at 8:30 a.m. Dec. 20, registered 2.2. On Nov. 24, a 2.4 came at 12:30 a.m. And last May 18, a 2.2 was recorded at 1:08 a.m.
"It's unusual to a small degree, but it's OK, fine," geologist Scott Howard said of Pageland's recent spate of earthquake activity. Howard is the chief geologist for the S.C. Department of Natural Resources' Geological Survey. "Earthquakes tend to happen in bunches. Not that any one earthquake is the result of another earthquake, but there just may be some local readjustments going on around the earthquake.
"So, not unexpected, but unexpected. I'm not surprised by anything."
Earthquakes below about 2.5 or 3.0 magnitude, like the recent ones near Pageland and most across South Carolina, typically aren't felt unless a person is in an upper story of a tall building or happens to be near the epicenter.
Several hundred magnitude 2.0 earthquakes happen every day around the world, according to the Incorporated Research Institutions for Seismology. That is to say, they're pretty common, and they're pretty unnoticeable.
What makes South Carolina earthquakes somewhat unusual, though, is that the state does not sit near any major fault lines, or boundaries between tectonic plates in the earth's outer layer, the way the western United States does.
The state does, however, experience what are known as intraplate earthquakes. These are quakes that happen along faults, or cracks, within the earth's plates. Earthquakes can also happen because of pressure buildup near water reservoirs or plutons, which are plugs of rock within the earth's surface. A pluton likely was the source of the Pageland quakes, Howard said.
Between 10 and 20 earthquakes typically are recorded in South Carolina each year, but only about two to five of them are felt, according to the S.C. Emergency Management Division.
The strongest earthquake to shake the Palmetto State in recent years was a 4.1 magnitude in the Edgefield area on Valentine's Day 2014. That quake caused some visible but relatively minor damage, including bricks being pushed out of a column and cracks in a church building near the epicenter, Howard said.
Earthquakes are most expected in the Charleston area, particularly near Summerville, because of the faults in the earth there.
The Charleston area was the site of the largest earthquake ever recorded in South Carolina, a 7.3 magnitude quake in 1886. Sixty people died, many others were injured, and damage amounted to tens of millions of modern day dollars.
If an earthquake that size were to strike the same area today, the S.C. Emergency Management Division predicts 900 people could die and another 9,000 could be seriously injured. Some 200,000 people could be displaced from their homes, and total economic losses could exceed $20 billion.
But it's practically impossible to predict earthquakes, at least in South Carolina, where tectonic plates are not a factor, as they are on the West Coast. Geologists have mapped where many of the state's fault lines are, but the timing of an earthquake all depends on stress buildup and when that energy decides to release itself.
"Earthquakes are a come-as-you-are disaster. We can't predict them, and we don't know where the stress is going to build up at any particular time to cause an earthquake," said Bill Clendenin, the state geologist for SCDNR's Geological Survey.
Is the recent pattern of small earthquakes in the Pageland area any indication that we could expect more — or greater — earthquake activity there in the future?
Probably not, Howard and Clendenin say.
"That's difficult to say, because if I say 'no,' then it will happen, and if I say 'yes,' then nothing will happen," Howard said. "I'm not too worried about earthquakes that occur in the central part of the state. Historical record, which is all anyone has to go on, suggests they're not going to get much greater than 5, and the Edgefield earthquake is an example."
"The real worry," he said, "is Charleston."