THEORIES ABOUT BIG BORDER BOOM

Camp Pendleton, bolides, planes all cited as possibilities

There is no shortage of theories among readers about what caused the Big Border Boom that rattled a large swath of San Diego and Tijuana on March 10.

Their suggestions were prompted by a story published recently in the Uniontribune and the Los Angeles Times exploring the boom and other unexplained noisemakers here and across the U.S.

Earthquakes? Sonic booms by spy planes? The weather?

One reader in Vermont pointed to bolides — meteors that explode when entering the Earth’s atmosphere — because they had one there around the same time. Another reader suggested weapons tests by planes flying off aircraft carriers at sea. She said that was the explanation on the East Coast a while back.

The military came up several times in emails and phone calls from readers. One pointed to Camp Pendleton, the Marine Corps training base near Oceanside. A noise advisory section on the base’s website shows they were “firing high explosive munitions” on March 10.

It also says, “Depending on atmospheric conditions, the sound of the explosions may be amplified and heard up to 50 miles away.”

But the Marines also fired high-explosive munitions on March 9, 11 and 12. If that was the source of the Big Border Boom, why weren’t loud, window-rattling, door-shaking noises felt on the other days, too? And why were the effects of the March 10 incident reported mostly in San Diego and Tijuana,

and not in North County?

One possible explanation came from a National City resident, a retired Naval aviator with a longtime interest in meteorology. He remembered reading about incidents in Arizona in which sonic booms from a military testing area were heard and felt some 50 miles away — carried there by jet streams, the meandering air currents in the upper reaches of the atmosphere.

Another reader forwarded a 150-page report that the Naval Research Laboratory in Washington, D.C., compiled after a string of “startling acoustic events” disturbed coastal residents of New Jersey and South Carolina from Dec. 2, 1977, through Feb. 15, 1978.

The report looked at the “historical record of unexplained noises” and explored many possibilities, including meteorites, winter lightning and nuclear detonations. It identified the likely cause as “high-performance military aircraft operating supersonically.” In other words, sonic booms.

Several readers noted that these kinds of mysteries have been around a long time. One pointed to the Lewis and Clark Expedition in the early 1800s, which “recorded hearing booms like distant cannons on the upper Missouri River.” Another went back even farther.

“Just finished your article in the newspaper and am reminded of something I discovered during my postgraduate studies at SDSU,” he wrote. “Unfortunately, I can’t remember the source of the information, but I read that early Spanish settlers in this region were told of the BOOMS by local Kumeyaay.”

He concluded: “A great atmospheric phenomenon, methinks.”

john.wilkens@sduniontribune.com