Don't blame Mother Nature for the mysterious rumblings that have shaken California five times since June. Experts say the culprit may be a speedy spy plane the Air Force says doesn't exist.
San Gabriel Valley residents, the latest group to report a rumble, believed they felt a minor earthquake Thursday morning.But seismologists at the U.S. Geological Survey in Pasadena said their instruments didn't register an earthquake. They said the shaking was caused by a sonic boom from an aircraft flying over the valley.
"All I can say is that it's something that's traveling through the atmosphere at several times the speed of sound," said Jim Mori, a seismologist with the U.S. Geological Survey in Pasadena.
Analysts from Jane's Defense Weekly, the London-based military periodical, said the rumble could have been caused by a top-secret new spy plane, called the Aurora, which reportedly flies at about 4,000 mph.
The Air Force denies that any such aircraft exists.
The mysterious rumblings, felt from Los Angeles County to Yuba County, north of Sacramento, have occurred five times since June, always about 7 a.m. on Thursdays.
Seismologists said the aircraft leaves a distinct signature on the seismograph, and it's unlike any plane they know.