The USGS said the incident occurred 3 kilometers north-northeast of Hammonton, New Jersey, at around 1:30 p.m. ET. There have since been reports of several secondary booms and tremors following the first event.
Despite what was felt and heard, according to the U.S. Geological Survey, it was not an earthquake, but a sonic boom. The National Weather Service also says it was a sonic boom.
The Navy says that flight testing done Thursday afternoon may have resulted in the sonic booms.
"Aircraft from Naval Test Wing Atlantic were conducting routine flight testing in the Atlantic Test Ranges this afternoon that included activities which may have resulted in sonic booms," the Navy said in a statement.
Reports of the apparent tremors were immediately all over social media:
7 earthquakes in a row in Jersey?? What is going on, they're getting stronger and stronger! The whole house is shaking— Paris Monroe (@ParisMonroe) January 28, 2016
Police in South Jersey are asking people to stop calling 911 to report the shaking.
There were reports of shaking felt in Long Island as well.
@ABC7NY felt 3 separate tremors in Bellmore Nassau county— Steven Seidler (@srock68) January 28, 2016
But what causes a sonic boom?
NASA describes it as "the thunder-like noise a person on the ground hears when an aircraft or other type of aerospace vehicle flies overhead faster than the speed of sound or supersonic."
As NASA puts its, "Air reacts like a fluid to supersonic objects."