LEBANON — A loud boom shook homes in the Upper Valley around 1:00 p.m. on Friday afternoon. Its source remains unclear.

“It was so quick, so brief,” said Elizabeth Borowsky, who lives in Lebanon. “It felt like a quick explosion.” It shook her house and her windows rattled. Her dog stirred from its nap, confused.

One possibility is that people heard a sonic boom, which occurs when an object, such as a jet, travels faster than sound and shock waves travel through the air.

An official from the 104th Fighter Wing of the Massachusetts Air National Guard said that their jets were in the Upper Valley area around the time of the boom for training.

The unit flies F-15 jets, which are capable of flying at supersonic speeds. But the official said that he doubted that was the source of the boom — when the jets took off from base, he heard nothing.

In 2013, an extremely loud noise was heard from Norwich to Vershire. An official from the Lebanon Municipal Airport air traffic control tower said that he learned from the Federal Aviation Administration traffic agency in Boston that there were F-15 jets in the area. Administration officials said that they could have caused the boom, but that they couldn’t be positive.

On a page on how to distinguish an earthquake from a sonic boom, USGS advises that a report of a supersonic boom typically covers a large area with no corresponding seismic record. USGS Survey also advises that shallow earthquakes often make a bang. USGS records earthquakes across the country, but recorded nothing in the Upper Valley Friday afternoon.

A little after 2:00 a.m., there was a minor, 2.1 magnitude earthquake in Maidstone, Vt.

“The final step is getting the military to admit responsibility,” writes USGS. “In most cases, the best we get is a confirmation that there were planes in the area that ‘might have gone supersonic.’ ”

In White River Junction, Dawn Dahlstrom also heard a loud boom that rattled her home.

It sounded and felt like an explosion, she said.

“It scared the daylights out of me,” she said.

On Facebook, nearly 250 comments built up on her Facebook post by 4:30 p.m. as people in towns including Hanover, Norwich and Quechee said they felt it too and wondered at its cause.

Claire Potter is a Report for America corps member. She can be reached at cpotter@vnews.com or 603-727-3242.