Science

Chile quake may have shortened day

The 8.8-magnitude Chilean earthquake released so much energy that it may have slightly shortened the length of the Earth's day, a NASA scientist says.

The 8.8-magnitude Chilean earthquake released so much energy that it may have slightly shortened the length of the Earth's day, a NASA scientist says.

Richard Gross, a researcher at the Jet Propulsion Laboratory computed how the Earth's rotation may have been affected by the Feb. 27 quake, which has killed at least 723 people.

The JPL computer model suggests that the length of the Earth day may have been shortened by 1.26 millionths of a second.

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The change in the length of the day came as a result of the shift in the Earth's axis that occurred because of the quake. The Earth's figure axis, the imaginary line about which its mass is balanced, shifted by 2.7 milliseconds of arc, or about eight centimetres.

Gross said the same model estimated that the 2007 Sumatran earthquake, with a magnitude of 9.1, should have shortened the length of day by 6.8 millionths of a second, although its shift in the Earth's axis was only about seven centimetres.

Gross said the smaller Chilean earthquake had a greater effect on the Earth's rotation because it occurred farther away from the equator. As well, the fault responsible for the Chile quake dips into the Earth at a steeper angle, making it more effective at shifting the axis.

Gross said more data from the Chilean earthquake will provide a clearer picture of how it affected the planet.

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