SPRUCE PINE — People across North Carolina and beyond were shaken by a far-reaching morning earthquake this past weekend.
Just after 8 a.m. on Sunday, Aug. 9, a 5.1 magnitude earthquake struck near Sparta, North Carolina. The shaking was felt all across North Carolina and reached as far as Georgia, Tennessee, Virginia and South Carolina.
The National Weather Service said the earthquake is the largest to hit the state since 1916.
The United States Geological Survey said the quake’s epicenter was 2.5 miles southeast of Sparta at a depth of about 2.3 miles.
Alex Glover, a licensed geologist living in Little Switzerland, said when he felt the shaking, he initially suspected high winds.
“I felt the whole house creaking,” he said. “I looked outside and there was no wind. The water in my horse trough tank was sloshing. I told my wife we were having an earthquake.”
Glover’s phone immediately lit up with activity as friends and colleagues picked his brain about the event.
“My phone rang off the hook,” Glover said. “Everyone was calling.”
Glover said the widespread tremors from the earthquake could be explained by the shallow epicenter.
“The epicenter was about four kilometers or about two miles deep,” Glover said. “That’s shallow for an earthquake. The more shallow, the more you feel because they’re not so deep. They’re not as resistant so they’re able to shake more.”
Glover said the earthquake could have originated from a splay off the Brevard fault— a 325 million-year-old fault at the foot of the Blue Ridge.
“It’s a big, famous fault,” Glover said. “It’s the most famous in North Carolina.”
The Brevard fault runs from Cartersville, Georgia all the way up to Marion and up into Sparta. Beyond that, it continues into Virginia.
“It could have been movement on that fault,” Glover said. “That’s what brought the Blue Ridge rocks over the Piedmont rocks.”
Glover said that such movement on the fault would be rare and suggested another explanation could be an old, failed rift suture.
“That’s where the crust was trying to pull apart and never totally pulled apart,” he said. “Where it is pulled, it leaves a weakness and sometimes those slip because there is so much pressure.”
Glover said massive pressure builds up on old, ancient sutures and faults will crack or slip.
Glover said Mitchell County is part of the East Tennessee Seismic Zone which is known for many, small earthquakes.
One this large, he said, is truly a rarity.
The USGS also reported that the force of the earthquake in the epicenter was roughly equivalent to 274-tons of TNT— similar to the force of the explosion in Beirut earlier this month.
“People are fascinated with earthquakes,” Glover said. “We are not at a plate tectonic boundary. We don’t normally get big faults like they do in California or other places. They’re not really rare but they aren’t abundant, either. The ones we do normally get are mostly small.”