Dr Stuart Sipkin, Director, World Data Centre for Seismology at the US Geological Survey in Denver, Colorado, says most of the island of Sumatra did not move at all.
In an e-mail interview to Senior Features Editor Archana Masih, the geophysicist at USGS' National Earthquake Information Centre said the earth's rotation should have been affected but the change is too small to measure, even by the precise techniques of today.
It is being said that the earthquake off the coast of Sumatra has shaken the earth on its axis and moved Sumatra, its neighbouring islands and the Andaman and Nicobar islands 15 to 20 metres from the geographical positions? Is this correct?No. Models predict that the rotation rate of the earth should have been affected, but the predicted change is too small to measure, even by today's very precise techniques. Most of the island of Sumatra did not move at all. The northwestern tip of the island, as well as the neighbouring islands moved somewhat, but by less than a metre. This motion was a combination of vertical and horizontal offset.
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Has this ever happened in the last 100 years? When was the last time an earthquake created a change in geographical positions?
Yes. Any earthquake with a magnitude of 9 or greater will have a similar effect. In the last 100 years earthquakes of this size or greater occurred in 1952, 1957, 1960, and 1964. However, see my answer above for how much change in geographical position actually occurred.
What does this mean for the region, what does it mean for the earth itself?
Since the change is much less than inferred by your questions, it does not mean that much geographically. Such changes have been occurring for billions of years.
Would an earthquake and tsunami destroy or damage the marine life in the Indian Ocean? Have you been able to quantify the human, ecological, marine loss?
The tsunami has certainly affected marine life in the near coastal areas. It probably had no effect on marine life in the deep ocean basin. The loss is still not well known, and may never be very accurately known.
What has been reaction of your seismologist community to this earthquake and tsunami. Are you stunned by its fury, devastation and magnitude?
The seismological community is still reacting to this earthquake. Although we all knew that earthquakes like this occur, they occur so infrequently that no one was really ready for it.
Is the region still vulnerable to similar earthquakes and tsunamis?
Similar earthquakes will occur in the future, although the next one may not occur during this century.
What other affects is this earthquake going to have on other parts of the earth?
In terms of geography, not much.
Does the earth shake on its axis for any other reason? Has it ever shaken because of an earthquake in the past?
Every earthquake of this size has a similar effect. While this effect can be numerically modelled, it is too small to be observed.
Is there any reason why this earthquake was such a powerful one?
While this was a huge earthquake, it is not unprecedented. Earthquakes of this size have been occurring throughout the history of the earth, and will continue to occur.
The India plate is moving closer to the Burma plate at an average rate of around 6 centimetres a year, for how long has this movement taken place. Would the movement continue after the earthquake and rupture of the ocean-bed?
This motion has been taking place for millions of years, and will continue in the future.