A relatively rare East Coast earthquake centered just northeast of South Carolina's capital city jolted large numbers of state residents awake early Monday, rocking the Southern state at a preliminary 3.3 magnitude, authorities said.
There were no immediate reports of any damages or injuries.
The pre-dawn temblor lasted only seconds but a number of people took to social media to describe being shaken from sleep when the quake hit shortly after 1:30 a.m. A seismic analyst monitoring the quake for the USGS Geological Survey's National Earthquake Information Center in Colorado, called it the latest in a series of shakes in recent months but stronger than usual.
"There's definitely been a 'swarm' here over the past several months. It's not like a swarm like after a large seismic event but we have had a number of them in recent months," geophysicist Amy Vaughan with the 24-hour monitoring service told The Associated Press by phone.
Vaughan said the 3.3 magnitude is an early assessment and could change, adding the quake occurred about 1.9 miles (3.1 kilometers) below the earth's surface near the community of Elgin. The epicenter was about 21 miles (3 kilometers) northeast of downtown Columbia, the capital city.
Those awakened reported feeling the earth shaking for several seconds and some even described what sounded like a heavy truck moving nearby. Vaughan said only an hour afterward she had reports pouring in to the quake monitoring center.
"I have not heard of any damage reports so far but have had over a thousand ... reports," she said. "If people were sleeping they obviously would have been woken up and things might have been rattling off shelves or countertops but not the kind of shaking or intensity to cause damage of any significance."
Still, she called it "alarming for sure" and said some lesser aftershocks were possible in coming days or weeks. She noted there were quakes of a preliminary 2.0 or higher in April and March and others going back little more than four months in the region — and a 3.3 quake last December.
She said the quake was a rather shallow one, fairly close to the surface, which made it felt, adding the area has been experiencing other shocks recently.
Two dozen minor quakes have rattled near Columbia since the end of last year, more than the 20 typically averaged by the state in an entire year, according to the South Carolina Emergency Management Division. Elgin is along a large fault system that extends from Georgia through the Carolinas and into Virginia.
Last year, the area near Jenkinsville — about 40 miles (60 kilometers) west of this group of tremors — registered six small earthquakes in over a week, with three quakes registered on a single day alone.
According to emergency management officials, about 70% of South Carolina earthquakes are located in the Middleton Place-Summerville Seismic Zone, about 12.4 miles (20 kilometers) 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.
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Meg Kinnard can be reached at http://twitter.com/MegKinnardAP.