Jets Cause Waves On Coast Sonic Booms Trigger False Tsunami Warnings, Panic Portland Area Residents

Fri., March 22, 1996

Associated Press

Military jets staging a mock battle rocked northwestern Oregon with a pair of sonic booms Thursday, panicking some coastal residents who thought a tidal wave was headed their way.

The booms, just before and after 9 a.m., felt like earthquakes to people from Astoria on the northern coast to Albany, 160 miles to the southeast.

Authorities in Cannon Beach, population 1,300, activated the tsunami warning system, sending virtually the entire town to high ground.

In Tillamook, the rickety old courthouse was evacuated.

“When you feel the ground shake in those low areas, you move,” said Joanne Spencer, of the Tillamook County emergency management agency. “You don’t take time to question it, because if it’s a close earthquake, that tsunami is going to hit in 20 to 30 minutes.”

The noises were caused by three Oregon Air National Guard F-15 fighter jets and two Air Force B-1 bombers that had joined a military exercise off the coast.

The Navy said it was a routine exercise that also involved three Pacific Fleet ships firing missile to sea about 45 miles offshore.

“We’re really sorry for scaring anybody, and hope things are getting back to normal,” said Mona Spenst Jordan, an Air National Guard spokeswoman.

Air Force and National Guard aircraft routinely fly at supersonic speeds off the coast, but must stay at least 30 miles to sea and above 10,000 feet to avoid sending any sonic boom inland.

The jets were 100 miles offshore, Spenst Jordan said, but atmospheric conditions apparently amplified the sound and caused a highly unusual atmospheric disturbance.

She said the Air National Guard flies about 16 training missions a day out of its Portland Air Base, and most are flown off the Oregon Coast.

“We go supersonic every single day and nobody hears us,” she said. “We did the same kind of maneuvers we always do. How we ended up sending a sonic boom into the coast is a mystery to me.”

People in the Fort Clatsop area near Astoria reported that the earth shook for about 20 seconds after the boom. Spencer said the sound was so loud it was obvious it could not have been made by a single jet.

“It was more than just a boom. There was a lot of rattling and it seemed to move. That would explain why it lasted so long,” she said.

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