Not only has South Carolina seen a surge in earthquake activity this week, but those ground-shaking events have been tightly concentrated in one location.
The U.S. Geological Survey records that earthquake activity this week has been concentrated in an area east-southeast of the town of Elgin in Kershaw County, near Interstate 20. The two largest quakes on Wednesday, the biggest South Carolina has seen in nearly a decade, had epicenters less than a mile from each other.
Both the 3.5 and 3.6 magnitude quakes Wednesday reverberated across the Midlands from the same square mile, a wooded area between Rio Lane and K-Land Road, both running from a line of trees and Whiting Way, an access road off of I-20, about 3 miles southwest of U.S. 601, according to mapping on the USGS website.
At least 18 smaller quakes have originated in the past week in the same general area, the survey shows. That includes 1.5 and 2.2-magnitude earthquakes recorded Friday morning.
Geologists say there is little clear reason why the Midlands should be having so many and such strong earthquakes right now.
“If you can figure that out, you should go get your tux and pick up your Nobel Prize,” said Thomas Pratt, regional coordinator of the Geological Survey’s earthquake hazard program. “The Eastern United States in general is not on a plate boundary, so it’s a mystery in the scientific community why in this exact location, in the middle of a plate, that something would trigger this.”
While minor earthquakes are not that unusual in South Carolina — state officials stress that several faults run through the state — the current stretch of quakes may be the most active in the state’s recorded history, geologists say.
The area near the epicenters does include a rock quarry, but while mining activity has been shown to disrupt underground rock pressure and produce quakes, Pratt said the existing quarry is too longstanding and does not significant enough activity to produce such sudden and powerful effects. The S.C. Department of Health and Environmental Control has also ruled out mining as a cause of this week’s quakes.
Both of Wednesday’s quakes were counted as South Carolina’s largest since a 4.1-magnitude quake struck McCormick County in 2014. Another An earthquake in Georgia on June 18 reached a 3.9 magnitude and could be felt in much of South Carolina.
While the recent rash of earthquakes has been minor so far, geologists warn that it could portend more serious shakes to come.
“Sometimes these can be foreshocks to a larger earthquake,” Pratt said. “Right now, there’s no reason to think there will be, but it can’t be eliminated.”