- Joined Jun 22, 2008
Chile earthquake may have shortened length of Earth's days
The powerful 8.8 magnitude earthquake that struck Chile, killing more than 700 people and triggering a tsunami alert, may also have shifted the planet's axis and shortened the length of each Earth day.
Richard Gross, a Nasa scientist, has worked out that the Earth's rotation should have changed as a result of the Feb. 27 quake.
Usinga complex model, he and fellow scientists came up with a preliminarycalculation that the earthquake should have shortened the length of anEarth day by about 1.26 microseconds (a microsecond is one millionth ofa second).
Mr Gross also calculated that the earthquake should have moved Earth's figure axis by 2.7 milliarcseconds (about 3 inches).
Bycomparison, Mr Gross said the same model estimated the 2004 magnitude9.1 Sumatran earthquake should have shortened the length of day by 6.8microseconds and shifted Earth's axis by 2.32 milliarcseconds (about2.76 inches).
He said that even though the Chilean earthquake wasmuch smaller than the Sumatran quake, it was predicted to have changedthe position of the figure axis by a bit more for two reasons.
First,unlike the 2004 Sumatran earthquake, which was located near theequator, the 2010 Chilean earthquake was located in Earth'smid-latitudes, which makes it more effective in shifting Earth's figureaxis.
Second, the fault responsible for the 2010 Chilieanearthquake dips into Earth at a slightly steeper angle than does thefault responsible for the 2004 Sumatran earthquake. This makes theChile fault more effective in moving Earth's mass vertically and hencemore effective in shifting Earth's figure axis.
"It's what wecall the ice-skater effect," David Kerridge, head of Earth hazards andsystems at the British Geological Survey in Edinburgh told Bloomberg.
"Asthe ice skater puts when she's going around in a circle, and she pullsher arms in, she gets faster and faster. It's the same idea with theEarth going around if you change the distribution of mass, the rotationrate changes."