NASA: Quake shifted Earth's axis, shortened day
Apart from claiming the lives of hundreds of people and wreaking
enormous property damage, Chile's massive earthquake has likely altered
the distribution of the Earth's overall mass, scientists from NASA say.
As a result, the length of a day is now a little shorter than it was
before Saturday's magnitude 8.8 earthquake.
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Picture of a boat left stranded in the middle of a hill after a
tsunami in the Chilean city of Dichato, some 30 km from
Concepcion. Pictures courtesy - AFP |
"The length of the day should have gotten shorter by 1.26
microseconds (millionths of a second)", Richard Gross, a geophysicist at
NASA's Jet Propulsion Laboratory, told Bloomberg.
"The axis about which the Earth's mass is balanced should have moved
by 2.7 milliarcseconds (about 8 centimeters or 3 inches)".
The speed that the Earth rotates also increased slightly in 2004
following the earthquake that struck the off the coast of Sumatra,
Indonesia. That 9.1 earthquake shortened the length of an Earth day by
6.8 microseconds, scientists say.
The reason is that sudden changes in the dimensions of the Earth's
tectonic plates, like those experienced in the earthquakes in Chile and
Indonesia, can alter the velocity.
David Kerridge, the head of Earth hazards and systems at the British
Geological Survey in Edinburgh, likened the change in rotation speed to
what happens when a figure skater draws her arms in close to her body
while spinning. "As she pulls her arms in", Kerridge told Bloomberg,
"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". |
