Our stressed tectonic plate may be breaking
[ UniNews Vol. 14, No. 2
21 February - 7 March 2005 ] By Elaine Mulcahy
Australian and American researchers investigating forces exerted on the Indo-Australian tectonic plate have discovered that the considerable stresses on the plate could be leading to it breaking up.
ARC Professorial Fellow, Mike Sandiford, from the University of Melbournes School of Earth Sciences, has received new ARC funding for research aimed at understanding the forces that drive the motion of the Earths tectonic plates and the distribution of stresses that give rise to earthquakes such as the magnitude 9 Sumatran quake which caused the devastating Boxing Day tsunami.
Professor Sandiford says the research shows that as much as 10 per cent of the huge amounts of energy being created at plate connection points at Sumatra and Java are being transferred back into our plate and causing major stresses.
This is enough stress to contribute to mild earthquake activity in the central regions of the plate, such as in the Australian continent or central Indian Ocean, and provides clues as to why our plate has been slowly breaking up, he says.
The Indian Ocean quakes are, in effect, leading to the active rupture of the Indo-Australian plate into separate Indian and Australian plates. The new findings provide us with important information about the stresses that are driving this drawn out tectonic plate divorce.
The research, which was conducted in collaboration with Wouter Pieter Schellart of the Australian National University and David Coblentz of the Los Alamos National Laboratory in the US, was published in the journal Geology (27 January 2005).
Professor Sandiford says the research is also important for understanding why smaller intra-plate earthquakes such as the 1989 Newcastle quake, which occurred nowhere near the edge of the plate, take place. Up to now it has not been well understood why earthquakes occur in apparently safe zones in the centre of plates.
Earthquakes such as the 1989 Newcastle quake that killed 13 people and caused more than $1 billion in damages are just one manifestation of mild tectonic activity that has been affecting the Australian continent for the past five to 10 million years, he says.
The new research shows that stresses originating at points of collision between two plates are dissipated back into our plate, generating enormous internal stresses.
The ARC funded project will map the spatial and temporal pattern of this tectonic activity and relate it to the factors that drive the motion of the Indo-Australian plate.
This research will contribute to our understanding of the factors that drive plate motion, to earthquake risk assessment in Australia and other comparatively stable continental regions, and to the factors that have shaped our distinctive Australian landscapes, he says.
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