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Minor tremors still rumble weeks after larger SC earthquake

COLUMBIA, S.C. — Small earthquakes are still shaking the ground near South Carolina’s capital city. The U.S. Geological Survey said a 1.7-magnitude earthquake happened just after midnight Tuesday just east of Elgin. A slightly larger quake occurred eight hours later just a few miles away.

And around 11:30 p.m., a 1.7 magnitude quake was recorded 9 miles from Elgin.

The new quakes were reported more than two weeks after a larger convulsion and outside the window geologists typically expect for aftershocks. The tremors were the 11th, 12th and 13th earthquakes in just a few square miles since a 3.3-magnitude quake on Dec. 27.

The South Carolina Emergency Management Division said a 1.5-magnitude earthquake centered near Lugoff also hit last Wednesday morning.

Earlier last Wednesday, a 2.6-magnitude earthquake struck near Elgin, according to the U.S. Geological Survey. It was measured at a depth of 0.5 kilometers, officials said.

That area, a community of fewer than 2,000 residents near the border of Richland and Kershaw counties, has become the epicenter of a spate of recent seismic activity, starting with a 3.3-magnitude earthquake on Dec. 27. That quake clattered glass windows and doors in their frames, sounding like a heavy piece of construction equipment or concrete truck rumbling down the road.

Since then, a total of at least 10 more earthquakes have been recorded nearby, ranging from 1.7 to 2.6. No injuries or damage have been reported.

According to the SCEMD, the state typically averages up to 20 quakes each year. Clusters often happen, like six small earthquakes in just more than a week last year near Jenkinsville, about 38 miles west of the most recent group of tremors.

Earthquakes are nothing new to South Carolina, although most tend to happen closer to the coast. According to emergency management officials, about 70% of South Carolina earthquakes are located in the Middleton Place-Summerville Seismic Zone, about 12.4 miles northwest of Charleston.

In 1886, that historic coastal city was home to the largest recorded earthquake in the history of the southeastern United States, according to seismic officials. The quake, thought to have had a magnitude of at least 7, left dozens of people dead and destroyed hundreds of buildings.

That event was preceded by a series of smaller tremors over several days, although it was not known that the foreshocks were necessarily leading up to something more catastrophic until after the major quake.

Frustratingly, there’s no way to know if smaller quakes are foreshadowing something more dire, according to Steven Jaume, a College of Charleston geology professor who characterized the foreshocks ahead of Charleston’s 1886 disaster as “rare.”

“You can’t see it coming,” Jaume told The Associated Press on Wednesday. “There isn’t anything obvious moving or changing that you can put your finger on that you can say, ‘This is leading to this.’”

Typically, Jaume said that the recent quakes near Elgin — which lie along a large fault system that extends from Georgia through the Carolinas and into Virginia — would be characterized as aftershocks of the Dec. 27 event, since the subsequent quakes have all been smaller than the first.

But the fact that the events keep popping up more than a week after the initial one, Jaume said, has caused consternation among the experts who study these events.

“They’re not dying away the way we would expect them to,” Jaume said. “What does that mean? I don’t know.”

So what’s happening here? Channel 9 meteorologist John Ahrens said it’s hard to say.

In the bedrock and ground beneath us, there are multiple fractures or little cracks. According to the geology department at UNC Charlotte, these fractures are ancient -- hundreds of millions of years old -- and difficult to map out.

All it takes is a little slip or a little stress in those fractures and you’re going to get some shaking. Similar situations have happened in Winston-Salem recently and down in South Carolina’s Lake Monticello, which Meteorologist Ashley Kramlich covered.

These clusters happen for a while and then usually go quiet.

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