Authorities have confirmed that a sonic boom is the culprit of rumbles and ground rattles reported in portions of coastal New Jersey, Delaware, and Maryland shortly before noon Thursday. 

Naval Air Station Patuxent conducted two flights off the Atlantic coast, causing the sonic boom, the Maryland Emergency Management Agency said in a tweet shortly before 5:30 p.m. Thursday. 

A sonic boom is "the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion," according to wikipedia.org. 

Social media began lighting up shortly after noon Thursday with reports of rumbles and ground rattles, with many immediately speculating that an earthquake had occurred. 

"Any chance we just had a small earthquake?" Gina Callegari Truchan posted on Jersey Shore Hurricane News from Brick Township after seeing her front door shake "vigorously."  

Laura Cirino Huff wrote on Wildwood 365 that she "heard something" and saw windows "rattling" at her job in Cape May Court House.

Similar comments appeared on Facebook pages based in coastal Delaware and Maryland. 

John Bellini, a geophysicist with the USGS, said that the agency received calls about the activity and reviewed output from seismometers.

"We looked at the seismometers and didn't see anything that looked like an earthquake," he said.

Bellini said that seismometers only detect vibrations within the ground.

"Air blasts and super sonic booms don't get recorded," he said. "So if it's a sonic boom, thunder, or a transformer exploding, there's no chance of recording it unless it occurs right near the seismometer." 

In October 2012, a similar incident occurred, with speculation that a sonic boom was responsible.