Updated at 7:38 p.m.
Navy jets were the cause of the "mysterious" boom noise Friday afternoon, according to U-T San Diego.
The noise, which left thousands of San Diego County residents talking, were "sonic booms produced by a pair of F/A-18 fighter gets operating from the carrier Carl Vinson 32 miles west of San Diego," according to the newspaper.
Thousands in San Diego County say they heard a loud explosion around 1 p.m. Friday, but authorities have no explanation or confirmations.
Twitter and Facebook were abuzz with reports and questions like "Okay SD, what is happening?? was that an earthquake, an explosion, or something going wrong at MCAS Miramar?"
Another tweet from @BriceAssociates read, "Just had an earthquake in La Jolla, CA -or something just quietly blew up nearby."
San Diego Patch sites in the coastal cities of Imperial Beach, Coronado, Oceanside, La Jolla, Carlsbad and Encinitas contacted emergency services in their respective communities who stated they have received no reports of an actual explosion.
Authorities from the Navy to the Sheriff's Department also could not immediately provide confirmation, or an explanation.
San Diego police Lt. Andra Brown said she felt downtown SDPD headquarters jolt a bit from inside her fifth-floor office. Likewise, Maurice Luque, spokesman for the city Fire-Rescue Department, detected structural jostling akin to a weak earthquake at his workplace.
Brown said two citizens, one in La Jolla and one in the Sunset Cliffs area, made emergency calls to report rattling windows and distant booms seemingly emanating from the west.
Sheriff's Lt. Paul Robbins said his agency had received "a couple" of calls from the public about the mysterious rumblings, but none that merited patrol call-outs.
No damage or injuries have been reported.
A Marine Corps Air Station Miramar spokesperson denied claims that it came from the base. Camp Pendleton is conducting range operations, but can't confirm that the sound came from the base, a base spokesperson said.
The U.S. Geological Survey has measured no significant seismic activity around the time of reports.
A similar boom was heard and felt in April which was measured with instruments in multiple locations across San Diego's North County. At a Scripps Institution of Oceanography facility in Carmel Valley the lights were knocked out momentarily by what was believed to be an infrasonic tremor.
Infrasound means sound below what humans can hear, and tremors can be triggered by "volcanoes, earthquakes, lightning, aircraft, meteors, and ocean waves" or other activities.
Kris Walker, a Scripps geophysics scientist who wrote a report on the boom, concluded that he was not able to say with total certainty what caused the noise and rumble.
Lightning, meteors, earthquakes and volcanoes were ruled out, but he believed the noise may have come from military activity far off the coast.
On most days when military exercises are taking place far offshore the noise cannot be heard by the human ear.
"However, certain atmospheric conditions may conspire to open up temporary 'infrasonic pipelines' that permit loud infrasound to travel far," he said in the report.
He believes the same traveling sound may have occurred Friday.
"When you have really strong winds in the atmosphere blowing from the areas where there is sound toward us, you can sometimes get these tunnels that carry sound, and you can hear something that's happening 50 miles away," he said.
Similar trembles and noises were common in the past during naval warfare exercises off the coast, he said.
"It would be interesting if there was top secret activities or a meteor or something, but I'm sure there's nothing unusual happening," Walker said.
City News Service contributed to this report.