anand
10th January 2005, 11:59 AM
The world "rang like a bell" after the Sumatra earthquake. Shock waves produced by the magnitude 9.0 quake would have circled the world several times a day, possibly for days, Clive Collins, a scientist with Geoscience Australia, said.
Mr Collins said earthquakes sent seismic waves in every direction. "Some pass right through the world, others travel around it, on the surface," he said. "They get to to the other side but they won't stop . . . they keep travelling. They just get smaller and smaller."
Surface waves travelled "fairly slowly, probably three or four kilometres a second. Because they are very low frequency waves you can't feel them."
Others hit the Earth's mantle or its molten iron core and bounced back. The result was that the Earth reverberated like a bell, or a water-filled balloon.
Although scientists are yet to analyse the seismic waves from the Boxing Day quake, it is expected they will be similar to those produced by the 9.5 magnitude Chilean quake that rocked the world in 1960.
"Following the Chile quake, the world oscillated for at least three days," Mr Collins said. When eventually analysed, the waves would give scientists a look deep inside the planet. "It's a bit like giving the world an ultrasound," he said.
Meanwhile, scientists continue to dismiss any link between the Boxing Day quake and a massive 8.1 magnitude quake that struck near Macquarie Island, south of Tasmania, on Christmas Eve.
"The occurrence of two great earthquakes within such a short space of time is indeed striking," a statement on the United States Geological Survey's website said. "However, we do not yet see evidence for a strong causal relationship between the two earthquakes."
The Macquarie Island quake was "very far" from Sumatra "and occurred on a different plate boundary". The two events were probably "a coincidence".
The US scientists say the Sumatra quake may have changed the world, including the speed of its rotation.
"In places, the block of crust beneath the sea floor (but above the fault line) is likely to have moved in the order of 10 metres to the west-southwest."
News from:www.theage.com.au/news/Asia-tsunami/ Seismic-waves-strike-to-the-core/2005/01/03/1104601250230.html
Mr Collins said earthquakes sent seismic waves in every direction. "Some pass right through the world, others travel around it, on the surface," he said. "They get to to the other side but they won't stop . . . they keep travelling. They just get smaller and smaller."
Surface waves travelled "fairly slowly, probably three or four kilometres a second. Because they are very low frequency waves you can't feel them."
Others hit the Earth's mantle or its molten iron core and bounced back. The result was that the Earth reverberated like a bell, or a water-filled balloon.
Although scientists are yet to analyse the seismic waves from the Boxing Day quake, it is expected they will be similar to those produced by the 9.5 magnitude Chilean quake that rocked the world in 1960.
"Following the Chile quake, the world oscillated for at least three days," Mr Collins said. When eventually analysed, the waves would give scientists a look deep inside the planet. "It's a bit like giving the world an ultrasound," he said.
Meanwhile, scientists continue to dismiss any link between the Boxing Day quake and a massive 8.1 magnitude quake that struck near Macquarie Island, south of Tasmania, on Christmas Eve.
"The occurrence of two great earthquakes within such a short space of time is indeed striking," a statement on the United States Geological Survey's website said. "However, we do not yet see evidence for a strong causal relationship between the two earthquakes."
The Macquarie Island quake was "very far" from Sumatra "and occurred on a different plate boundary". The two events were probably "a coincidence".
The US scientists say the Sumatra quake may have changed the world, including the speed of its rotation.
"In places, the block of crust beneath the sea floor (but above the fault line) is likely to have moved in the order of 10 metres to the west-southwest."
News from:www.theage.com.au/news/Asia-tsunami/ Seismic-waves-strike-to-the-core/2005/01/03/1104601250230.html