Quake shifted Japan coast 2.4 metres, tilted Earth's axis

Mar 12, 2011, 11:57 GMT

Berlin/Washington - Japan's strongest earthquake on record that triggered a destructive tsunami appears to have moved the main island by 2.4 metres and shifted the Earth on its axis, scientists said Saturday.

'We know that one GPS station moved (2.4 metres), and we have seen a map from GSI (the Geospatial Information Authority) in Japan showing the pattern of shift over a large area is consistent with about that much shift of the land mass,' Kenneth Hudnut, a US Geological Survey geophysicist, told broadcaster CNN.

Italy's National Institute of Geophysics and Volcanology said according to preliminary results of a study it conducted that Friday's 8.9-magnitude quake shifted the Earth on its rotation axis by nearly 10 centimetres.

This quake's impact on the axis was much greater than that of the 9.1-magnitude Indonesian earthquake in 2004, and probably second only to the Chilean quake of 1960, said the institute's director, Antonio Piersanti, in a statement.

In 2010, scientists from US space agency NASA said the 8.8- magnitude earthquake that struck Chile that February was so strong that it may have shortened the length of a day.

Using a computer model, Richard Gross, a scientist at the space agency's Jet Propulsion Laboratory in California, found the quake likely shifted the Earth's axis by about 8 centimetres.

The shift of the axis on which the planet's mass is balanced slightly changes the length of time it takes the Earth to make a complete rotation - after the Chilean quake it meant that each day was about 1.26 microseconds shorter. A microsecond is one-millionth of a second.

The infinitesimal shift was slightly more than a similar change after the 2004 tremblor, Gross said. Even though the magnitude of the Chilean quake was slightly less, its location and the angle of its fault lines made it more likely to shift the axis.

The 2004 earthquake and tsunami in Southeast and South Asia permanently speeded up the Earth's rotation, shortening the succeeding days by about three microseconds, Gross said then. The time change occurred when that quake moved the Earth's axis by 2.5 centimetres.

About 1,000 people are feared dead in Japan's quake and tsunami. The Meteorological Agency said more than 100 aftershocks had occurred since Friday, many of them over 6 on the Richter scale.

Japan is located on the Pacific 'Ring of Fire,' an area prone to seismic upheaval and volcanic activity because it lies on the edges of tectonic plates.

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