Mystery Jolts Defy Explanation

It was about 12:30 p.m. on a Saturday, June 29, when they struck: Two unmistakable, concussive vibrations that shattered a handful of windows and set off car alarms en masse.

Coming just 29 hours after the deadly, 6.0-magnitude Sierra Madre earthquake, the vibrations unnerved more than a few people along the Orange County coast.

“It seemed like the whole building rose up off the ground and slammed back down,” said Brian Boyle, who operates the Main Street Emporium clothing shop on the Balboa Peninsula. “It was amazing.”

By now, Boyle’s windows have been repaired. Shaken residents have gotten on with their lives. But the rumblings remain anonymous and unclaimed--two orphaned June jolts.

Local police, civilian aircraft regulators, Coast Guard and other military officials say that they do not know what caused the jolts. Seismologists at Caltech have no answers either, other than to say the jolts were not earthquakes.

Still, inquiring minds want to know: What caused them?

“I haven’t heard a thing,” said Boyle, owner of the Balboa clothing shop. “I called the El Toro Marine base, and the guy didn’t give me any information at all. So I just ended up eating it ($1,500 of window repairs) myself. We unfortunately don’t have glass breakage on our (insurance) policy. . . . Boom--there goes three storefront windows in one unexplained thing.”

Another of the curious is Bill Cacace, owner of Great Lengths for Hair, a salon on Pacific Coast Highway in Corona del Mar. Cacace’s shop was doing a brisk business June 29. When the shaking stopped, his 10-by-12-foot storefront window was shattered, his customers briefly scattered.

“It took about 2 1/2 weeks” to make the repairs, Cacace said. “. . . We did have some people drive by and think that we were closed up. But I don’t think it hurt our business.”

Cacace said his landlord’s insurance company has paid for $1,400 in repairs. Has he gotten answers about the cause?

“No,” Cacace said. “None at all. I’ve heard it wasn’t the military. It wasn’t an earthquake. I have a sneaking feeling it was either Navy or Air Force, doing maneuvers off one of the islands. . . . But there is no proof, one way or the other.”

The closest base for the type of aircraft capable of producing sonic booms is the El Toro Marine Corps Air Station. But from the outset, officials there have disavowed knowledge of what could have caused the jolts.

Asked Thursday whether the Marines had yet picked up any clue of what happened, a spokeswoman, Capt. Betsy Sweatt, said: “There’s nothing new.”

El Toro Marine Capt. C.B. Rydelek provided this two-paragraph response last month to a request for information filed by The Times:

“This correspondence responds to your Freedom of Information Act request of 12 July, 1991 . . . in which you seek access to any report prepared by this command regarding a sonic boom that occurred along the Orange Coast at or about 12:30 p.m. on Saturday, 29 June, 1991.

“A thorough search of our records has failed to disclose information responsive to your request. Accordingly, no further action is deemed appropriate, and your request is returned without the report you requested. Thank you.”