Killer quake altered earth

After the devastating earthquake of December 26, the earth is probably slightly rounder, the days slightly shorter and the North Pole presumably shifted towards the east.

These are some of the calculations made by Nasa scientists after they made a study of the impact of the earthquake that registered nine on the Richter scale and caused tsunamis which took the lives of more than 156 000 people.

The scientists said in a statement that, although all earthquakes had an impact on the earth, this one - with its megathrust - "was definitely something totally out of the ordinary".

They calculated that the earth staggered a few centimetres on its axis, that days will be three microseconds shorter (a microsecond is one millionth of a second) and that the North Pole has shifted 2.5 cm to the east.

The scientists reckon earth is rounder than before and is also rotating faster around its axis, which result in shorter days.

Professor Kobus van der Walt, lecturer in physical geography on the Potchefstroom campus of Northwest University, says that earth is not a round ball but has an elliptical form.

As a result of rotation, the earth bulges slightly at the equator and the poles are slightly flattened.

Earth rotates around an imaginary "earth axis", which runs through the two poles, says Van der Walt.

He says the movement of the earth plates which caused the earthquake has changed the form of the earth slightly with the result that the bulging at the equator is now slightly less than before.

This causes earth to rotate slightly faster around its own axis.

This is similar to an ice-skater who rotates at a specific speed with outstretched arms and then pulls in the arms to increase the rotational speed.

None of these changes have yet been measured - only calculated.