1st snow, then quake rattles Southerners
The kind of magnitude-4.1 earthquake that rolled out from its epicenter near Aiken, S.C., on Friday night was a once-every-two-decade event, and Southern quakes, it turns out, are far different in origin and impact than the plate-grinding temblors of California.
The South Carolina earthquake alarmed millions of residents who'd just finished digging out of a rare Southern snowstorm, and emergency centers in South Carolina and Georgia lit up bright shortly afterward.
The quake occurred at 10:23 p.m., according to the U.S. Geological Survey. Centered 7 miles west of Edgefield, S.C., it could be detected far to the north in Hickory, N.C., as well as 150 miles away to the west, in Atlanta, where local Facebook boards recounted with mild alarm what was by then a mere computer screen shaker.
Nevertheless, “it's a large quake for that area,” USGS geophysicist Dale Grant told The Associated Press. “It was felt all over the place.”
Large earthquakes are few and far between in the Southern piedmont. Georgia felt a magnitude-4.3 quake in 1974, fairly near to Friday night's epicenter. Three similar-size quakes have been experienced in South Carolina since 1970.
South Carolina bore the brunt of the largest-ever earthquake on the East Coast — a magnitude-7.3 earth-shaker that killed at least 60 people in post-Civil War Charleston, in August 1886.
Although South Carolina is laced with small faults that can cause earthquakes, the state as a whole rests fairly firmly right in the middle of one of the North American plates.
According to geologists, the Valentine's Day Quake may have been caused by the subterranean breakdown of the ancient Appalachian Mountains.
In the West, extensive underground bouldering limits the expanse of seismic shockwaves, but such waves travel more easily and farther through the sandier Appalachian detritus. East of the Rockies, an earthquake can be felt over an area as much as 10 times larger than a similar magnitude earthquake on the West Coast, according to the USGS.