San Diegans responded Thursday to reports of shaking and a loud noise in various areas of the county.
The mysterious incident may have a possible answer Thursday night.
The event may have been caused by a meteorological phenomenon generated by the contrast of hot and cold air masses, according to the Center for Scientific Research and Higher Education in Ensenada. The clash of masses produces a rumble that can cause windows to vibrate.
In Spring Valley, NBC 7 follower Luis Hernandez said he was in front of Monte Vista High School when he felt the ground begin to shake.
He said his friends felt it too. He described it as an earthquake.
Other NBC 7 Facebook followers from San Carlos, Granite Hills, Imperial Beach, Downtown, El Cajon, Carmel Valley, Bonita, Bankers Hill, Lakeside, National City, Tijuana, Barrio Logan, Otay Ranch and Eastlake said they felt the rumbling or heard their windows rattle.
Alexa Robles said, "Shook the roof to our office building. Off market street near the 94 and 30th."
"Thought it was guys working on building next door at first," Marvin Ramirez said from San Carlos.
The U.S. Geological Survey, the agency that monitors earthquake activity, has no reports of a quake in our area.
The San Diego County Sheriff's Department told NBC 7 they don't know of anything happening that may have led to the noise or the rattling.
A spokesperson for the Naval Air Forces, U.S. Pacific Fleet checked with USS Vinson off the coast of San Diego.
He said a plane flying at supersonic speeds off the coast could produce a noise felt this far away but pilots don't normally start flight operations until noon.
As of 11 a.m., the crew was conducting air operations. Even so, the spokesperson could not confirm the sound and shaking reported in San Diego is directly attributed to carrier operations.
According to a spokesperson for Camp Pendleton, they were conducting a routine motor training but it is unlikely that this caused the sonic boom.
The Deputy Director, Communication Strategy and Operations 3d Marine Aircraft Wing, MCAS Miramar 1stLt Casey M. Littesy told NBC 7 there were no reports from 3rd Marine Aircraft Wing that the unit caused the noise.
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