Chile quake shifted Earth's axis?

LONDON: The earthquake that struck Chile on Saturday may have shifted the Earth’s axis and created shorter days, according to scientists at Nasa. Richard Gross, a geophysicist at Nasa’s Jet Propulsion Laboratory in Pasadena, California, said the 8.8 magnitude quake could have moved the Earth’s axis by 2.7 milliarcseconds (about 8cm) - enough to shorten a day by about 1.26 microseconds.

A large quake can shift huge amounts of rock and alter the distribution of mass on the planet. When that distribution changes, it changes the rate at which the planet rotates, which determines the length of a day.

Gross previously used the technique to estimate the shift caused by the 2004 Sumatran quake that caused the Indian Ocean tsunami. That 9.1 magnitude quake shifted the Earth’s axis by 2.3 milliarcseconds and shortened a day by 6.8 microseconds. David Kerridge, a seismologist with the British Geological Survey, said the Chile and Sumatra earthquakes were based on subduction, in which one tectonic plate slides under another, redistributing the Earth’s overall mass. The effect was similar to that for an ice dancer who moved their arms in and out to accelerate and slow their spin. Earthquakes caused by plates sliding past each other, such as the recent event in Haiti, do not have the same impact on the Earth’s rotation.