Residents of Columbia County are wondering what, or whom, is responsible for the boom.
Residents on and near Louisville Road near Appling reported hearing, and feeling, a loud boom early this morning.
"It woke me out of a dead sleep," said Terry Glasscock. "You could feel the vibration. It wasn't like the whole house shook, but you could feel it."
He said he went outside to see if a transformer had blown to discover his neighbors outside as well, also investigating the noise.
"I know the rock quarry blast. We hear the siren and can sometimes feel that, but this was a little different."
He said he felt something similar about six weeks ago, but did not report it.
Columbia County Emergency and Operations Division Director Pam Tucker said the proximity of the reports to the Easter Piedmont Fault indicated it might be an earthquake and is following up with seismologists.
"It's crazy," she said. "I don't know what it is. We get these reports from time to time, but it's a fairly recent phenomenon.
The anomaly, she said, are two reports, one received Wednesday and another Tuesday, of similar booms in other parts of the county. She said the earlier reports might not be related.
"That could be something like a potato cannon," she said, referring to a common culprit. "There are people that just like loud noises and blowing stuff up."
The last recorded earthquake in Columbia County was April 23, 2012 and registered 2.3 on the Richter scale and had an epicenter near Appling. Tucker said for people to hear a quake, it has to measure at least 2.0 on the Richter scale.