Thursday, April 9, 2009

sonic boom might be source of latest 'mystrey'shaking

The U.S. Geological Survey and Caltech are investigating whether a sonic boom is the likely cause of the latest round of mysterious window and door rattling in Orange County.

Residents across most of the county reported the rattling between 12:15 p.m. and 12:19 p.m. today. It’s not yet known whether the Navy or Marines have been flying supersonic F-18s off the coast.

“I was talking to (seismologist) Kate Hutton and she said she was getting reports of a possible sonic boom-like shaking just after noon,” said Bob Dollar, a seismologist with the U.S.G.S. “We’re looking into it.”

There have been no significant earthquakes in Southern California today. There was a 4.6 quake in the Gulf of California at 12:02 p.m., and many peope from Orange County reported feeling shaking from the event. But that’s likely an error, says Dollar.

“I’ve never heard of a quake of that size being felt that far away (more than 1,000 miles,” Dollar says.

Orange County experienced similar window and door rattling on March 3 and March 16. The precise cause of both events hasn’t been identified.

It also appears that the artillery fire going on at Camp Pendleton today didn’t cause the shaking.

Camp Pendleton issued a special advisory earlier this week saying that the base would be conducting round-the-clock artillery and high explosive exercises through Thursday that could produce sounds and vibrations felt up to 50 miles away — or all the way to the north end of Orange County.

Pendleton officials said such long distance vibrations would occur only if the “atmospheric conditions” were right. Usually, such vibrations and sounds travel farthest when there’s cloud cover and moisture in the air, says the National Weather Service. Most of the county is currently sunny. But clouds are expected to bring light showers later. There have been no significant earthquakes in Southern California today. unknown if the Navy or Marines are flying F-18s close to the coastline today at speeds fast enough to produce a sonic boom.

The latest shaking has been reported by people in Newport Beach, Tustin, Laguna Beach, Mission Viejo, Trabuco Canyon, Ladera Ranch, Yorba Linda and Laguna Niguel.

Cindy McNatt, a Register reporter, said by instant message, “I live in a glass house (in Tustin) — so I was watching the glass rattle, but didn’t feel anything on the ground.”

Erika Ritchie, another Register reporter, said, “I was sitting in my house and the windows on the top floor started to shake so loudly that my dog barked because it sounded like someone was trying to force open a door. The bamboo floor also began shaking beneath me.

A reader named Nate from Lake Forest e-mailed to say, “At about 12:19 p.m., a big rumble shook our house. Thought it may be a tremor or a small earthquake. But not sure what’s up.”

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