Japan quake makes Earth spin faster, rocks axis

Did yesterday seem to pass a little more quickly than usual? Maybe that's because it was shorter - and it's all because of the massive earthquake that struck Japan last week.

US space agency NASA's Jet Propulsion Laboratory in Pasadena has calculated that the quake caused the Earth's rotation to speed up by 1.8 microseconds (millionths of a second).

Friday's earthquake, which measured 8.9 on the Richter scale, caused a sudden shift in the Earth's mass. Seismologists liken the effect to that of a figure skater pulling their arms in, causing them to rotate more quickly.

NASA's calculations also show that the Japan quake has shifted the position of Earth's figure axis - the theoretical line along which the Earth's mass is balanced - by roughly 17cm or 6.5 inches.

NASA geophysicist Richard Gross was keen to reassure people that the changes wouldn't affect people's daily lives.

"These changes in Earth's rotation are perfectly natural and happen all the time," the scientist explained in a press release. "Earth's rotation changes all the time as a result of not only earthquakes but also the much larger effects of changes in atmospheric winds and oceanic currents."

A larger 2004 earthquake in Sumatra, measuring 9, caused the day to shorten by 6.8 microseconds.

The Japanese earthquake was the fifth strongest since records began in 1900.