[lit-ideas] ok, this is somewhat stunning
- From: JimKandJulieB@xxxxxxx
- To: lit-ideas@xxxxxxxxxxxxx
- Date: Thu, 19 May 2005 15:19:34 EDT
_Click here: CNN.com_ (http://www.cnn.com/)
and we seem already to have forgotten......
Scientists: Sumatra quake longest ever recorded
Temblor big enough to 'vibrate the whole planet '
By Marsha Walton
CNN
(CNN) -- Dramatic new data from the December 26, 2004, Sumatran-Andaman
earthquake that generated deadly tsunamis show the event created the longest
fault rupture and the longest duration of faulting ever observed, according to
three reports by an international group of seismologists published Thursday in
the journal "Science."
"Normally, a small earthquake might last less than a second; a moderate
sized earthquake might last a few seconds. This earthquake lasted between 500
and
600 seconds (at least 10 minutes)," said Charles Ammon, associate professor
of geosciences at Penn State University.
The quake released an amount of energy equal to a 100 gigaton bomb,
according to Roger Bilham, professor of geological sciences at the University
of
Colorado.
That's about as much energy as the United States uses in six months -- or
the power of 5 million bombs the size of the atom bomb dropped on Nagasaki.
And that power lasted longer than any quake ever recorded.
The quake, centered in the Indian Ocean, also created the biggest gash in
the Earth's seabed ever observed, nearly 800 miles. That's as long as a drive
from northern California into southern Canada.
Scientists estimated the average slippage (ground movement up and down)
along the entire length of the fault was at least 5 meters (16.5 feet) -- with
some places being moved nearly 20 meters (50 feet).
Scientists have also upgraded the magnitude of the quake from 9.0 to between
9.1 and 9.3, a dramatically more powerful event. As a comparison: the ground
shook 100 times harder during December's earthquake than what was felt in
the 1989 Loma Prieta quake in California. That 6.9 magnitude quake caused
extensive damage from Santa Cruz to San Francisco.
Monster quake
The stunning power of Asia's earthquake and tsunamis last December has left
even veteran scientists in awe.
"I think it was humbling for everyone that analyzed the earthquake," said
Thorne Lay, professor of earth sciences and director of the Institute of
Geophysics and Planetary Physics at the University of California, Santa Cruz.
"We're sitting in our laboratories working on the signals from this
earthquake, trying to understand what happened scientifically, and then
watching TV
at night and seeing the death toll rising for weeks," he said.
The enormous human toll from the natural disasters spurred Lay to organize
dozens of scientists from all over the world to share their data and analysis
of the quake. The long-term goal is to try to get more, and more accurate
tsunami warning systems in place.
Whole planet vibrated
A wide array of instruments were used for the first time to study the
earthquake, and its many aftershocks.
Global broadband seismometers recorded the ground in Sri Lanka, a thousand
miles from the epicenter, moved up and down by more than 9 centimeters (3.6
inches), according to the report.
But no place on Earth escaped movement.
"Globally, this earthquake was large enough to basically vibrate the whole
planet as much as half an inch, or a centimeter. Everywhere we had
instruments, we could see motions," Ammon said.
Much of that information came from digital broadband seismometers, a new era
of instruments that the National Science Foundation and the U.S. Geological
Survey began deploying around the world several years ago.
Lay says the equipment is sensitive enough to pick up the motion of wind
blowing through trees, or cows walking in a field, or the massive motions
produced by this earthquake.
"We'd never seen signals from an earthquake of this size, and the
availability of this instrumentation was a real breakthrough in being able to
see the
complete rupture process of one of these truly monstrous events," Lay said.
Other tools added to the scientists' understanding. Underwater cameras
documented the huge crack in the ocean floor. Tsunami buoys, and sonar from
the
British Navy helped with the analysis.
And a fortunate bit of timing enabled researchers to get a view of the
tsunami they have never seen before.
"Two hours after the earthquake has occurred, the wave is spreading out from
the Bay of Bengal," Lay said. "Two satellites went over, with the capability
of measuring the elevation of the ocean surface. The satellites saw the
south-going wave and the north-going part of the wave. "It was just good luck
that the passage of the satellites caught the tsunami in motion," he said.
Crunching numbers, and creating maps and models is taking on a new urgency
for some of the scientists involved in this research.
"There will be more earthquakes of this type, and with more humans exposed
to the hazard there will be more devastating losses of life. What we hope to
do is develop technologies that can minimize that loss," Lay said.
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