Literally earth-shaking, quake shifted the pole
Friday, December 31, 2004
BY KITTA MacPHERSON
Beyond killing tens of thousands and unleashing a humanitarian crisis of
epic proportions, the twinned earthquake and tsunami that struck Southeast
Asia Sunday altered the angle of the Earth on its axis, moved the North
Pole, pushed walls of water throughout all the world's oceans and shifted
the soil as far away as Newark, researchers are reporting.
Scientists said yesterday they are looking beyond the tragedy to try to
extract meaning from an event of such magnitude. They want to learn how the
Earth responds as a system to one of Nature's terrible jolts. And they
wonder about the Earth's resilience. "It's a tragedy but it's a source of
data for seismologists," said John Armbruster, an earthquake expert at the
Lamont-Doherty Earth Observatory in Palisades, N.Y. "People will be studying
the recordings of this earthquake for months and will be talking about it at
conferences for years."
In one of the worst natural disasters in history, the earthquake and
subsequent tidal wave killed at least 117,000 people, by yesterday's
estimates, and forced up to 5 million from their homes.
Calculations performed by Richard Gross of NASA's Jet Propulsion Laboratory
in California show that the quake sped up the rotation of the Earth and
enlarged its wobble, causing the length of a day to shrink permanently by 3
millionths of a second. It also moved the North Pole 1 inch, he found.
Gross, a geophysicist who studies the Earth's rotation, attributes the
changes to a redistribution of mass. The fissure that opened on the floor of
the Indian Ocean during the quake swallowed so much matter that it changed
the balance of mass on the Earth, he said. "If you can imagine an ice skater
pulling her arms in as she spins, to cause her to spin faster, that's sort
of what happened in this case," Gross said. About 1,000 years from now, the
length of an Earth day will increase by about a second because of the event,
One of the perplexing scientific questions for Tom Herrington, a graduate
professor at Stevens Institute of Technology's Center for Maritime Systems,
is whether the tsunami generated by the quake will affect the underlying
circulation patterns of the oceans, such as the Gulf Stream. It's possible,
The tsunami propagated a huge underwater wave that acted more like a tide,
scooping water from the bottom and surging through the world's oceans, he
said. The waves most people think of, he said, are propelled by wind. Not
this one, he added.
"We've often theorized how waves like that would propagate," said
Herrington, an ocean engineer. "Now we can look at it, in a forensic sort of
way, and better understand it. From our standpoint, it's a learning
Though the event occurred in a very "uninstrumented" part of the world,
Herrington said, scientists will be able to access satellite data to help
them in their analysis.
Researchers at the Lamont-Doherty facility in New York, part of Columbia
University, have been tracking earthquakes for decades and say their
instruments showed that the quake rang the Earth like a bell. Seismic waves
emanated from the epicenter, like ripples moving out from a pebble thrown
onto a pond surface.
Armbruster, the Lamont-Doherty seismologist, said that, though he hasn't
completed his analysis, he believes the quake moved the soil in the Newark
and greater metropolitan area by a half- inch. The temblor on the other side
of the world pushed the ground up that far, then back down the same
distance. The movement was so swift, it was not noticed by residents of the
region, he said.
A well-studied 1964 quake in Alaska of a greater magnitude moved the ground
in New York up 2 inches and then down 2 inches, he said.
Some seismic waves, like the ones that moved the soil, travel along the
surface of the Earth. Others course through the center of the Earth. Such
waves caused by this quake will prove fascinating to seismologists and
geologists, Armbruster said, who want to better understand the density and
strength of the rocks at Earth's core.