NSF PR 96-39 - August 5, 1996
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Scientists Study Undersea Volcano during Earthquake
'Swarm'
The most intense 'swarm' of earthquakes ever recorded
in Hawaii is now occurring at the Loihi undersea volcano,
according to National Science Foundation (NSF)-funded
oceanographers at the University of Hawaii.
The summit of Loihi seamount is more than 3,200 feet
below the surface of the ocean and some 20 miles southeast
of the big island of Hawaii. More than 2,000 earthquakes
have been recorded in this area since July 16th with
more than 40 quakes at a magnitude larger than four
on the Richter scale.
Anticipating that this earthquake activity is accompanied
by an undersea volcanic eruption, oceanographers at
the University of Hawaii will embark August 5 on a
six-day research cruise to Loihi on the research vessel
Kaimikai-O-Kanaloa.
"Instruments on the ship will be used to observe possible
changes in the depth of the ocean floor," says the
cruise's chief scientist, Fred Dunnebier of the University
of Hawaii, "and to take samples of hot water rising
from the volcano." Microphones in the water will also
listen for earthquakes and the sounds of eruptions.
If weather and safety considerations permit, a manned
submersible will dive on the seamount to observe the
possible eruption and to collect rock and water samples,
adds Dave Epp, director of NSF's marine geology and
geophysics program, which funded the expedition.
"Though the Loihi earthquakes are small," explains
Epp, "they are considerably larger than those associated
with Kilauea's eruptions, so they may signify more
than just an eruption going on. Probably what is happening
is a succession of slumping events as the steep sides
of Loihi collapse." Slumps and landslides are of significant
concern, since when they move they displace seawater
and can generate a tsunami, or tidal wave. But a slump
large enough to generate a dangerous tsunami would
result from a magnitude six or larger earthquake --
big enough to be felt as strong shaking along the
adjacent Puna and Ka'u coasts of the big island. "The
problem is that the travel time of a tsunami from
Loihi to the coast is only a few minutes," says Dunnebier.
"The moral is clear: If you feel the Earth shake,
get away from the ocean."
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