Small earthquakes are still shaking the ground near the South Carolina capital, more than two weeks after a larger convulsion and outside the window than geologists typically expect aftershocks to.
Early Tuesday, a magnitude 1.7 earthquake struck just east of Elgin, about 40 kilometers northeast of Columbia, according to the US Geological Survey. It was measured at a depth of 3.2 kilometers, officials said.
About eight hours later, a slightly larger earthquake, 2.0, occurred a few miles away, officials said.
The tremors were the 11th and 12th earthquakes over a few square kilometers since December 27, when a magnitude 3.3 earthquake slammed windows and glass doors into their frames. The event, which lasted a few seconds, looked like a heavy construction machine or a concrete truck driving down the road. None of the earthquakes caused significant damage, the agency said.
Since then, a total of 11 additional earthquakes have been recorded nearby, ranging from 1.4 to 2.6. No injuries or damage were reported, although experts expressed dismay at the events.
Earthquakes happen in South Carolina every year, and sometimes there are clusters. The state typically experiences an average of up to 20 earthquakes per year, according to the South Carolina Emergency Management Division. Last year, six small earthquakes occurred in just over a week near Jenkinsville, about 38 miles (61 kilometers) west of the most recent cluster of quakes.
Elgin, a community of less than 2,000 near the border of Richland and Kershaw counties, sits along a vast fault system that stretches from Georgia to the Carolinas and Virginia. However, most South Carolina earthquakes tend to occur closer to the coast in the Middleton Place-Summerville seismic zone, about 12 miles northwest of Charleston.
On January 5, as small earthquakes continued to erupt near Elgin, a magnitude 1.4 earthquake struck that area further south, the state’s only geographic aberration among recent earthquakes.
But the Charleston area is one that traditionally comes to mind when thinking about earthquakes in South Carolina. In 1886, this historic coastal city was home to the largest recorded earthquake in the history of the Southeastern United States, according to seismic officials.
The earthquake, which is said to have had a magnitude of at least 7, killed dozens of people and destroyed hundreds of buildings. In the days leading up to it, the region experienced a series of smaller tremors, although it is not known that the first tremors necessarily led to anything more catastrophic before the major earthquake.
In the current scenario, geologists view the South Carolina sequence as aftershocks from the magnitude 3.3 earthquake of December 27, rather than a sign of more severe seismic activity, although the window is be extended longer than expected.
“It certainly lasted longer than a typical main shock and aftershock streak,” Steven Jaume, professor of geology at the College of Charleston, told The Associated Press Tuesday.
With no known end in sight, Jaume said the tremors continued to confuse experts already accustomed to being baffled by the puzzling phenomena.
“It’s not over until it’s over,” Jaume said. “Earthquakes are one of the least predictable natural hazards. “
Meg Kinnard can be reached at http://twitter.com/MegKinnardAP.