Small plate movement caused killer quake
Dr Roger Musson, a seismologist with the British Geological Survey in Edinburgh, said the fault line running under the Indian Ocean was 1,200km long, 500km wide, was in three sections, and that it had moved just 15 metres.
He explained: “It happened because of the fact that the whole of the Indian-Australian plate is moving northwards.
“This will happen again in the future over the next several million years and has been happening for several million years in the past.”
He said the fault under the Indian Ocean was much bigger than the San Andreas fault in California.
“The San Andreas fault is more or less vertical so no matter how long it is it can only go about 30km down because that is the width of the crust. But this thing is dipping gradually so is probably 500km wide as well as several thousand km long in total, so it’s got much more potential for big earthquakes than the San Andreas has. An earthquake like this could not happen at the San Andreas.”
Dr David Booth, also a senior seismologist with the group, said earlier: “The earth displacement associated with this earthquake has generated a Tsunami, a tidal wave. “Not all earthquakes will do this. First of all the earthquake has got to curve underwater in the ground under the ocean and also the movement of the rock has got to reach the surface.
“Where there is a displacement of the ocean floor, it causes a movement on the surface and it spreads out from there at a speed of about 500km an hour. It’s fast, but slow enough for warning to be given, if a sophisticated warning system is set up.”
Dr Booth said he was aware of a warning system in the Pacific but he was not aware of a warning system being set up round the Indian Ocean where the colossal earthquake was born.
“This wave may only be a few metres high in the ocean but as it reaches shallow water the wave builds up very quickly in height and these waves can be reportedly 50 metres high.”
Dr Booth explained: “The ocean floor is being pushed under the continent and enormous stresses build up and because the length of the fault is very long you have the potential for a very large earthquake as the whole fault moves as one.”
Just after 1am this morning vibrations were picked up by instruments in Britain, 5,000 miles away.
“Our instruments have recorded the tremor here. In fact this is the largest we have seen with regards to displacement in instruments. The waves generated would have travelled all around the world.”
