A loud boom shook the coastal Lowcountry Wednesday morning, felt from Mount Pleasant to West Ashley. And once again, no one could say what it caused it.
Seismographs at the College of Charleston didn't pick up any earthquake activity. The Charleston Air Force Base didn't report any military aircraft creating sonic booms.
No commercial vessels responded to a U.S. Coast Guard message asking for reports if it had been felt offshore.
The reverberation most likely came from the "Seneca Guns," a so-far-unexplained phenomenon felt along coasts around the world.
Some experts speculate that the booms are caused by gases released from the sea floor, or undersea landslides along the Continental Shelf, or the echoed sound of distant thunder, or lightning-like electrical discharges, or even meteors crashing into the atmosphere at angles.
The latest blast hit just before 10 a.m.
"It was a pretty good shake, a pretty loud boom," said Mark Reamer, who felt it in the Financial Management
Group office off Coleman Boulevard near Patriots Point in Mount Pleasant.
"I said it was probably one of those big electricity pillars getting pummeled down." He wondered only half-facetiously if it might have been a piece of the satellite that fell out of orbit last week.
"The mirrors on the wall rattled," said Melinda Issacson, who was working out at home on James Island.
Doors, windows and houses shook in Mount Pleasant and on Sullivan's Island, according to Twitter reports. A West Ashley tweeter said it sounded like a gust of wind against the house.
About the same time, a large tree fell across Hut Road on Johns Island and a nearby resident reported an explosion. But a tweeter in North Charleston said nothing was felt there.
Small quakes and other booms are regular occurrences in the Lowcountry, where a series of faults converge underground. The last big shake was a temblor from the 5.8 Richter scale quake in Virginia in August.
In March, a succession of three loud booms shook the coast that were widely believed to be the Seneca Guns.
Reach Bo Petersen at 937-5744 or follow him on Twitter at @bopete.