What is the likelihood of an earthquake in Horry County?

HORRY COUNTY, S.C. (WBTW) — At least a dozen earthquakes have shaken the Palmetto State so far in 2023, according to the state Department of Natural Resources.

However, an earthquake in Horry County isn’t really something you have to worry about. While the county does have a few geo-physically inferred faults, most of the risk is in the greater Charleston area.

An inferred fault basically means the fracture between two blocks of rock wasn’t directly observed, but deduced from previous seismic measurements.

“We’re not on a plate boundary. So, the stresses to break that kind of rock aren’t there anymore,” said Rich Viso, the associate dean of The Gupta College of Science at Coastal Carolina University. “But once it’s been broken, is broken, it can sit there and be locked and not move for a long time. But the fractures can still exist, so those would be the faults.”

Viso said the last time Horry County was seismically active was millions and millions of years ago and he doesn’t see earthquakes being a major concern for those in Horry County for another few million years.

“The earth is dynamic. There are constant shifts and adjustments going on large scale forces moving the surface of the planet,” he said. “And so earthquakes happen all the time, every day all over the planet. If we were to have an earthquake, it would probably be some shifting or adjustment on that crystal and rock where it would fracture and then the vibrations would affect the sediments overtop of it.”

The soil in Horry County is mostly made up of clay, loam and sand, which Viso says ups the chance of higher liquefaction if the quake is big enough.

“Soil just like we have now that we can walk around on, build buildings on, live our lives on, when you shake it at a certain frequency, or vibrate it, it can almost behave like a liquid and start to flow,” he said. “That would probably be our biggest hazard here.”

Horry County isn’t seismically active, however, the county’s emergency management have plans in place.

“It’s part of our comprehensive emergency plan,” Thomas Bell said. “So, it is something that we have looked at, we have thought about. So, as far an emergency management perspective, that is something that we would be ready to respond to and assist in the recovery after.”

Bell said it’s important to know what to do even if an earthquake is unlikely to occur in our area.

“And that’s like muscle memory, when we were all growing up, we learned, ‘stop, drop and roll’ when it came to fire. So with earthquakes, it is ‘drop, cover and hold on,’ meaning get low to the floor, cover your head,” Bell said.

Both Bell and Viso emphasize that while an earthquake likely won’t happen in Horry County during our lifetimes, it’s always good to be aware and have a plan in place.