12/31/2004

news@nature.com - Sumatran quake sped up Earth's rotation


News
Published online: 30 December 2004; | doi:10.1038/news041229-6
Sumatran quake sped up Earth's rotation
Michael Hopkin
Natural disaster shaved millionths of a second off planet's day.


The Earth has been rocked on its axis.
© NASA
The devastating earthquake that struck the Indian Ocean on 26 December was so powerful that it has accelerated the Earth's rotation, geophysicists have declared. They estimate that the shockwave shortened the period of our planet's rotation by some three microseconds.

The change was caused by a shift of mass towards the planet's centre, as the Indian Ocean's heavy tectonic plate lurched underneath Indonesia's one, say researchers at NASA's Jet Propulsion Laboratory in Pasadena, California. This caused the globe to rotate faster, in the same way that a spinning figure-skater accelerates by tucking in her arms.

The blast literally rocked the world on its axis, add Richard Gross and his NASA colleagues. They estimate that Earth now tilts by an extra 2.5 centimetres in the wake of the jolt.

news@nature.com�-�Sumatran quake sped up Earth's rotation

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