‘Extremely puzzling’: What’s causing frequent earthquakes at SC lake?

JENKINSVILLE, S.C. — With trees lining the shore, and the water still on a calm day, there’s something serene about Lake Monticello.

But what’s happening beneath the surface is anything but tranquil -- thousands of strange earthquakes, coming from the bed of a lake that was not made by nature.

“Wow, this is new,” said Dallas Kennedy. “You learn something every day.”

Kennedy said he comes to the shores of Lake Monticello to find a moment of peace. And while the lake’s surface is calm, what’s happening beneath it is anything but.

Rare earthquakes are happening here because man, rather than nature, created the lake.

“Heard of the earthquakes happening in the area but never knew it had anything to do with the lake,” said visitor Martin Miller.

It’s called reservoir-induced seismicity. It’s extremely rare, occurring at just a few man-made lakes around the world.

It happens when the reservoir is built over rocks that have tiny fractures. The weight of the water forces it to down into those cracks, which builds up pressure until, ultimately, that pressure forces the rocks to move -- and that is what creates an earthquake.

“Extremely puzzling,” Miller said. “I don’t see how it could relate to an earthquake.”

The reservoir was built in 1978 for the Virgil C. Summer nuclear power plant. It’s become a popular fishing spot.

Miller comes to the lake for white bass and perch. He said he knew earthquakes were rocking the area, south of Chester, but didn’t know the lake was causing them.

“It usually happens soon after a new reservoir is built,” said UNC Charlotte geologist Andy Bobyarchick. “What is less common -- continued earthquakes in the same reservoir.

Bobyarchick has been studying reservoir-induced seismicity for years but he told Channel 9 it usually only happens when a lake is new.

“It’s less common to have reoccurrences over intervals of years like we have seen in Monticello, so this is still a big question mark,” he said. “Still trying to figure this out.”

Lake Monticello is rare because small quakes keep happening years after the lake was created. Since Oct. 25, seven earthquakes have rumbled across Jenkinsville, South Carolina.

Fortunately, the quakes from Monticello are fairly weak.

“Too small to be felt, don’t tend to be damaging,” said Bobyarchick. “Localized and very shallow.”

There have been three reservoir earthquakes across the world that have registered 6 or stronger on the Richter scale, but those have all been in much deeper lakes where more water pressure can build up.

Lake Monticello is only 89 feet deep.

(WATCH BELOW: 1 year since 5.1 earthquake struck near Sparta, NC)