Literally earth-shaking, quake shifted the pole

Friday, December 31, 2004
Star-Ledger Staff

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, he said.

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, he said.

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 opportunity."

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.