At 4:49 p.m. Wednesday, a single boom shook houses, popped open shut doors and rattled pictures off walls from the northern Outer Banks to Columbia to Craven County.
But what caused that boom is a mystery.
The on-duty seismologist at the U.S. Geological Survey’s Earthquake Center scanned data for the area this afternoon and early evening and said there was no seismic activity.
“It wasn’t an earthquake,” she said.
The National Weather Service Newport/Morehead City forecast office received a call from Craven County Emergency Management about that time asking about it.
Meteorologists took a look at radar and atmospheric conditions and found nothing to explain the boom.
Though the region is home to, and close to, several military bases, the boom seems to have been felt across too broad an area to be a sonic boom or demolitions training, the weather service said.
The USGS has long researched a phenomena around the Outer Banks known as “Seneca guns,” but they say it’s just a name, not an explanation.
The storied phenomena refers to booms that have been heard and felt along the shores of Lake Seneca and Lake Cayuga in New York State, as well as the tidewater area of Virginia, the Outer Banks and along the Carolina coast.
Some Seneca guns reports have been explained as sonic booms from military jets, though other theories — like the movement of tectonic plates — have been disproved.
The Coastal Review Online, the news service of the North Carolina Coastal Federation, examined the phenomena in a 2012 story, speaking with a scientist who theorized that temperature inversions may be to blame.
“Temperature inversions occur in coastal areas when upwelling of cold water decreases surface air temperature and the cold air mass stays under warmer ones. What’s more, North Carolina’s coast juts out into the Atlantic, essentially creating a microphone effect,” the review wrote.
The effect would cause sound waves to travel, and amplify.
“With that in mind, it seems feasible that Seneca Guns boom loudest when an inversion layer amplifies a natural event, such storms far past the horizon; or a man-made situation, such as breaking the sound barrier,” the article said.
The USGS says there’s no agreement on a cause for Seneca guns, with most cases never explained.
“They have been occurring in several places around the eastern U.S. and in India for at least a century or two,” the agency says on its website. “The Earth is a complex place and there is a lot about it that we don’t understand. Perhaps someday we will understand what causes Seneca guns, but right now we don’t understand what makes them. However, they do not seem to pose a threat to anyone.”