March 2, 2010

NASA: Quake May Have Shifted Earth’s Axis

The February 27 earthquake that rocked Chile and killed more than 700 people possibly shifted the Earth's axis and shortened our day ever so slightly, a scientist with NASA told Bloomberg.

Earthquakes have the potential to shift hundreds of miles of rock by several meters, which can disrupt the planet and change the distribution of its mass. The Earth's rotation is affected by these changes, according to geophysicist Richard Gross of the Jet Propulsion Laboratory in Pasadena, Calif. Gross used a computer model to calculate the effects.

"The length of the day should have gotten shorter by 1.26 microseconds (millionths of a second)," Gross told Bloomberg in an email. "The axis about which the Earth's mass is balanced should have moved by 3 inches."

Though difficult to detect physically due to their small size, the changes can be modeled, said Gross. Some changes are more obvious. The massive tremor may have moved small islands, according to Andreas Rietbrock, a professor of Earth Sciences at the U.K.'s Liverpool University who has studied the area impacted from earlier earthquakes.

The latest quake may have displaced Santa Maria Island off the coast of Concepcion, raising it by as much as 6 feet, Rietbrock said in a telephone interview with Bloomberg. He noted that the rocks show evidence of being lifted from past quakes as well.

"It's what we call the ice-skater effect," David Kerridge, head of Earth hazards and systems at the British Geological Survey in Edinburgh, said. "As the ice skater puts when she's going around in a circle, and she pulls her arms in, she gets faster and faster. It's the same idea with the Earth going around if you change the distribution of mass, the rotation rate changes."

Rietbrock said the massive 8.8 magnitude earthquake made the Earth "ring like a bell."  He has not been able to get in touch with seismologists in Concepcion to discuss the quake and the effects it had created.

The 9.1 magnitude Sumatran quake in 2004 shortened the day by 6.8 millionths of a second, said Gross.


Image Caption: This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite.


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