The earthquake in Chile has probably shortened the length of the day by about 1.26 millionths of a second, according to Nasa.
The magnitude 8.8 quake may have moved the planet on its axis by about 7cm.
Dr Richard Gross, a scientist at Nasa’s Jet Propulsion laboratory in Pasadena, California, has calculated that the strength of the quake and its location resulted in a slight movement of the Earth's figure axis, around which the mass of the planet is balanced. One implication of the shift is that the speed of rotation around this axis has probably increased so that the day length has been shortened — a reversal of the historic process of the Earth's rotation slowing down and the days getting longer over millennia.
Dr Gross said that the Sumatran earthquake that caused the Boxing Day tsunami in Indonesia in 2004, which was magnitude 9.1, probably shortened the day length by 6.8 millionths of a second. The smaller Chilean earthquake caused a greater shift of the Earth because it occurred further from the equator.
Although the changes to the length of the day are so small as to be undetectable, they are permanent.