What caused the boom in San Diego County on April 4?

[Ivan Seeking]

Something of the sort happened in San Diego County shortly before 9 a.m. Tuesday, April 4, and so far no one has come forward with an explanation.

...Scientists insist it wasn't an earthquake. The Federal Aviation Administration has no record of any planes producing a sonic boom by breaking the sound barrier.

Camp Pendleton officials say no activities on the Marine base could have created such a disturbance. There were no large explosions in San Diego County that day, and no meteor fireballs were reported in the sky that morning.

What was it, then?[continued]

http://www.signonsandiego.com/news/northcounty/20060423-9999-1n23bigboom.html

 

[matthyaouw]

Sounds about the same as this one to me:
https://www.physicsforums.com/showthread.php?t=104565

 

[wolram]

Just a thought, high altitude wind direction is quite often different from lower
altitude wind direction, could some sort of friction between these winds
build up a charge that is given of as a (sprite) so one would here a boom
but see no discharge ?

 

[Ivan Seeking]

...The scientists, based at Scripps Institution of Oceanography in La Jolla, say the disturbance was caused by a sound wave that started over the ocean and petered out over the Imperial County desert. Using data from more than two dozen seismometers, they traced its likely origin to a spot roughly 120 miles off the San Diego coast.

Tracking the boom
That spot is in the general vicinity of Warning Area 291, a huge swath of ocean used for military training exercises. The Navy operates a live-fire range on San Clemente Island, which is within Warning Area 291 and sits about 65 miles from Mission Bay.

...“I would guess it's either an explosion that somebody hasn't told us about or it could have been a meteor coming into the atmosphere,” he said. “But it was certainly a big disturbance in the atmosphere.” [continued]

http://www.signonsandiego.com/news/metro/20060427-9999-1n27boom.html