NC State geologist on lessons from Sparta, Winston-Salem earthquakes

In August 2020, the biggest earthquake in North Carolina in over a century struck near Sparta and caused millions of dollars of damage. Karl Wegmann is a geologist at North Carolina State University who specializes in the study of landforms and the natural hazards that can come from them. He says the Sparta event will help geologists understand the state's topography.

“Prior to this event, there were no known active faults (a discontinuity between two rock types) in North Carolina,” he says. “The ground surface was physically broken by this earthquake, first documented surface rupture of an earthquake east of the Appalachian Mountains. So it's a pretty big deal. Prior to the Sparta earthquake happening, we wouldn't even have known where in North Carolina to look for past earthquake activity.”

The Sparta quake was several orders of magnitude larger than the series of microearthquakes that struck in the fall. Those events varied in size, from almost imperceptible to being felt by people as far away as Greensboro, according to the U.S. Geological Survey.

For comparison, the 5.1 magnitude quake that struck Sparta could be felt by people from the Gulf Coast to Canada, Wegmann says. He says the microearthquakes are not likely a harbinger of worse things to come. But we may continue to have them every decade or so.

“My guess is it's not a preview of a larger earthquake,” he says. “These are just very small events and the release of a little bit of stress that has built up in the shallow crust beneath the Winston-Salem area.”

He says other natural events such as hurricanes and floods are a much more consistent threat to North Carolinians than earthquakes. 

“I've been in North in North Carolina since 2008,” says Wegmann. “We've had, if you include the Virginia earthquake, which I felt in Raleigh, sort of two big earthquakes in the 15 years that I've been here. So we'll learn from the Sparta event, we'll be a little better prepared, hopefully for the next one.”

He says the lessons learned could lead to changes in such things as how foundations are constructed or standards for emergency response devices for critical infrastructure like liquid petroleum pipelines, hydroelectric dams or nuclear power plants. 

“As these events happen, it causes people to reflect and to look back and say, ‘Okay, do we have the safeguards in place?'” Wegmann says.

As for whether the mountains might be more prone to large earthquakes in the region, Wegmann says there's evidence that may not be true. The largest earthquake to hit the East Coast in historic times was in Charleston, South Carolina in 1886. That was far larger than the Sparta quake, strong enough to topple some chimneys in Raleigh, Wegmann says. And the Virginia earthquake near Richmond in 2011 occurred in a Piedmont region like the Triad.

“It does seem like we have large earthquakes in … all three of our physiographic provinces: the coastal plain, the Piedmont and the Blue Ridge/Appalachian Mountains,” Wegmann says.