Expert Sees More Aftershocks But No Killer Quake
Wed Dec 29, 2004 12:32 PM ET
By Philip Barbara
WASHINGTON (Reuters) - Strong aftershocks from the Indonesian earthquake will
be felt for "weeks and
months" but more killer-magnitude tremblers and deadly tsunamis were unlikely,
a geophysicist with the U.S. Geological Survey said on Wednesday.
Waverly Person, a USGS director, said he anticipates repeated and at times
powerful
aftershocks that will spread from the epicenter of Sunday's quake in the
Indian Ocean off Sumatra along a line about 600 miles long.
"I don't think there's any chance of a major earthquake of (magnitude 9)
but there will be continued strong aftershocks," he told Reuters from USGS
headquarters in Golden, Colorado.
He said USGS seismologists were aware of two quakes of magnitude 6.0 that
struck
on Wednesday alone.
The largest aftershock at 7.5 magnitude occurred, he said, about 3.5 hours
after
Sunday's main quake, the world's most powerful in 40 years that set off
tsunamis that barreled across the Indian Ocean before striking coastal areas
in south and Southeast Asia.
Deaths in the tsunami disaster could top 100,000 when figures for India's Bay
of Bengal islands are known, a senior international Red Cross official said.
Sunday's quake beneath the Indian Ocean seabed was caused when the India plate
dipped under the Burma plate, with the epicenter about 155 miles off the
Indonesian island of Sumatra.
"The ocean there is a hot zone for earthquakes," he said, adding that
aftershocks
"could continue for weeks or months," but "another one of magnitude 9.0
is highly unlikely."
As of Wednesday, he said, no USGS seismologists were planning to go to Asia
because the quake occurred under water, making it difficult to study. Still,
engineers will want to study the earthquake's damage to buildings wherever
possible.
"For us at USGS, this is not the first earthquake in this (undersea) area.
Quakes
of (magnitude) 7 occur often," he said.
"But this was the largest and it generated a tsunami. There isn't much known
about tsunamis, there's no history of them in the Indian Ocean, and so it's
more of an opportunity for scientists who study tsunamis."
An international team of Japanese and U.S. tsunami scientists will be going
to the region to conduct field work that will provide additional data about
the earthquake and advance understanding about earthquakes and tsunamis,
said Dr. Harold Mofjeld, a senior scientist with the U.S. National Ocean
and Atmospheric Administration.
"The tsunami field data provides important additional information about the
quake that can't be obtained by seismographic records," he said. "With this
data and using computer models, it's possible to back calculate the tsunami
source."
The team has to move quickly. "A problem with this study is that the scientific
evidence
of tsunamis tend to disappear rapidly as cleanup and humanitarian operations
go forward," he said.
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