DATE: Thursday, June 12, 1997               TAG: 9706120449

SECTION: LOCAL                   PAGE: B2   EDITION: FINAL 

SOURCE: BY CINDY CLAYTON, STAFF WRITER 

                                            LENGTH:   42 lines

F-18S CAUSED SONIC BOOMS THAT SHOOK AREA MONDAY

The mystery of the Monday morning booms has been solved.

The shaking and quaking felt by scores of folks from Suffolk to the Peninsula were caused by sonic booms generated when two F-18s flying off the coast of Cape Charles broke the sound barrier, said Kelly Burdick, spokeswoman at Naval Air Station Patuxent River, Maryland.

The planes, based at the Patuxent River station were flying a ``research and development'' mission, Burdick said.

She said that the planes were flying on a test route that runs along the coast, 30 miles off shore. She didn't know how close the planes were to Cape Charles when they broke the sound barrier.

She said the planes caused similar booms off the coast of Maryland on Monday. The planes were moved a greater distance off shore, Burdick said.

But the move farther out to sea may have been the reason houses across Hampton Roads shook and folks called 911 centers with questions about what had happened. Most callers said they heard the booms between 11:15 and 11:40 a.m.

Burdick said that, depending on the altitude of the plane and atmospheric conditions, sonic booms could be heard across great distances.

``As long as (the planes) are traveling at supersonic speeds, then yes, it is conceivable that you could hear them,'' Burdick said.

She said that a sonic boom is caused when air reacts with a plane that is flying at supersonic speeds.

NASA's Web site has a sonic boom fact sheet that explains the phenomenon this way:

As a plane moves through the air or over the water, air molecules are pushed aside - like fluid - with great force, creating a shock wave.

The wave forms a cone of pressurized air molecules that move outward and backward in all directions and extend to the ground. . . . The sharp release of pressure after the build-up of the shock wave is heard as the sonic boom.

The NASA site says that the intensity of the boom depends on the plane's altitude, speed and atmospheric conditions. The direction of travel and strength of shock waves also are influenced by atmospheric conditions.

More information can be found on the Internet on the Sonic Boom Homepage: (www.acs.psu.edu/users/tracie/sonic/boomhome.html).

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