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Antartica shakes too - 13/03/2000

Earthquakes are more frequent in Antarctica than previously thought, recent work by the Institute of Geological & Nuclear Sciences Limited (GNS) has shown.

Earthquake activity in Antarctica is not well understood mainly because of the lack of instruments in the continent, and seismometers in other parts of the world are too distant to accurately record Antarctic earthquakes.

GNS geophysicist Stephen Bannister is the first scientist to systematically measure earthquakes in the 3500km-long Transantarctic Mountains using an array of broadband instruments.

With assistance from Australian National University in Canberra, Dr Bannister recently placed 10 solar-powered seismometers at intervals of 25 to 30km through the mountain range to listen for earthquakes.

During the three months they were operating, the instruments picked up more than 50 local earthquakes of magnitude 2 to 4. None were recorded by seismograph stations outside Antarctica.

Dr Bannister said a few of the earthquakes were due to the movement of glaciers, but the rest were definitely tectonic in origin.

" The distribution of earthquakes may indicate a previously unknown fault in the Transantactic Mountains.

" The data collected this summer provides the first accurate measure that earthquakes are occurring regularly in Antarctica. It also provides the first ever three dimensional information on the crust beneath the central Transantarctic Mountains."

The new data, which will take months to fully analyse, will lead to meaningful progress in understanding the present-day processes occurring in Antarctica.

The instruments also picked up 50 large distant earthquakes from locations such as the South Indian Ocean, Chile, Papua New Guinea, Indonesia, and Peru.

Analysis of wave patterns from the distant earthquakes has provided new insights into geological structures up to 60km below the Transantarctic Mountains.

Determining the deep structures of the mountain chain will help scientists understand why the mountains have been uplifted by more than 4km over the last 50 million years.

" Understanding how the Transantarctic Mountains have evolved is fundamental to understanding how earth processes work," Dr Bannister said.

For more information contact:
Stephen Bannister