Mysterious Boom (San Diego county)
4/27/06

La Jolla-based scientists say a mysterious boom heard and felt
throughout San Diego County earlier this month originated from an area
over the ocean, but the source of the disturbance remains unknown.
According to scientists at the Scripps Institution of Oceanography, the
thunderous noise heard April 4 started over the ocean about 120 miles
off the San Diego coast and petered out over the Imperial County desert.

Scientists said the spot where the rattling boom originated is in the
general vicinity of Warning Area 291, a huge swath of ocean used for
military training exercises. The Navy operates a live-fire range on San
Clemente Island, which is within Warning Area 291 and sits about 65
miles from Mission Bay.
But Steve Fiebing, a Coronado-based Navy representative, said the
live-fire range on San Clemente Island was inactive April 4. He also
said there was no Navy or Marine Corps flight activity in Warning Area
291 on that day that would have caused a sonic boom or a countywide
tremor.

Peter Shearer, a Scripps professor involved in the research, has no idea
whether the disturbance was natural or made by humans.
"I would guess it's either an explosion that somebody hasn't told us
about or it could have been a meteor coming into the atmosphere,"
Shearer said.
The Scripps researchers believe the disturbance was the result of a
low-frequency wave that traveled through the air at the speed of sound
as it moved from the ocean to the desert. They said it was picked up by
more than two dozen seismometers in San Diego and eastern Riverside
counties.

The boom heard around 8:45 a.m. rattled homes and buildings all
throughout San Diego County, including residences in Ramona and the
county sheriff's building in Clairemont Mesa.
Some people speculated the disturbance was the result of an earthquake.
But the U.S.
Geological Survey said no measurable seismic activity was recorded in
the county that morning.



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