Sunday, 7 March 2010

Earthquake in Chile moved the Earth axis and 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.
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.

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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The powerful earthquake that killed hundreds of people in Chile on Saturday probably shifted the Earth's axis and made days slightly shorter, a Nasa scientist has said.
Richard Gross, a research scientist at Nasa's Jet Propulsion Laboratory in California, calculated how much the axis may have changed in position following the the disaster.
More than 700 people died and two million are estimated to have been affected by the 8.8-magnitude tremor and subsequent tsunamis.
The quake, the most powerful to hit the nation in 50 years, sent shockwaves out from the epicentre 70 miles from Chile's second city, Concepcion.
Buildings and roads collapsed and 500,000 homes have been left severely damaged.
Six aid workers died when a plane carrying them to Concepcion crashed.
The team was on its way to help organise accommodation for those left homeless by the disaster.
Soldiers were sent to patrol Concepcion's streets after mobs set fire to shops and started looting them, hindering attempts to rescue survivors.

If the planet's axis did shift by 8cm during the quake, days would have shortened by 1.26 microseconds, Mr Gross calculated.
A microsecond is one-millionth of a second.
Earth days are 24 hours long because that is the amount of time it takes the planet to make one full rotation on its axis, so shifting the axis would affect rotation.
The quake shifted the Earth's axis by even more than the 9.1-magnitude tremor off Indonesia that started the deadly tsunami in Asia in 2004, according to Mr Gross.
This was partly because the fault line responsible for the quake in Chile "dips into Earth at a slightly steeper angle than does the fault responsible for the 2004 Sumatran earthquake", he said.
The different angle made Saturday's tremor more effective at moving Earth's mass vertically and shifting the planet's axis, Mr Gross continued.
The 2004 quake in Asia, which killed hundreds of thousands of people, caused the Earth to move by around 7cm.
It chopped an estimated 6.8 microseconds off the length of a day, Nasa said.

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