Sonic waves also are commonly known to be mistaken for earthquakes, but officials at Dover Air Force base to the north and NASA Wallops Flight Facility to the south on the Delmarva said they had no activity to report.

Late in the day, the Navy owned up to scheduling two supersonic flights off the Atlantic coast Thursday from its test flight facility at Patuxent Naval Air Station in Southern Maryland.

That explanation satisfied the Maryland Geological Survey.

“At this time, we are confident that the supersonic flights were the cause of the felt reports,” Ortt said in an e-mail about 6 p.m. Thursday.

Base spokeswoman Connie Hempel said Friday that the jets, an F-35C and an F/A-18, were in the air from about 9:20 a.m. to 12:20 p.m. along a strip of airspace that runs along the Delmarva, up to 12 miles off the coast and 3 miles away at its closest. Weather officials at the base said the sonic booms the aircraft created could have likely traveled further than normal because a temperature inversion was in place, when there is warm air aloft holding colder air in place below, with calm winds and recent passage of a cold front, Hempel said.

Test aircraft from the air station make supersonic flights almost daily in the airspace off of the Delmarva shore, and the sonic booms they create are rarely felt on land, officials said.

Some nevertheless wonder if there wasn't something more mysterious. Rader said similar rumblings occur once every three or six months, and Thursday’s was the most intense yet.

“We’ve never got one like today,” he said.

Tribune reporters Michelle Deal-Zimmerman and Paresh Dave contributed to this report.