Calvert ready to sail for earthquake study

Feb 20, 2003, vol. 26, no. 4
By Diane Luckow

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Earth sciences professor Andy Calvert will be bouncing around on the ocean off the west coast of Vancouver Island this summer aboard the Japanese seismic survey vessel Karei.

He's part of a team collaborating on a seismic research project that will try to establish where the Cascadia megathrust fault is weakest and, from that, which populated areas might experience the strongest shaking during an earthquake.

The project, funded with about $1 million from the National Sciences and Engineering Research Council, involves experts from the Japanese marine science and technology centre, the University of Victoria, UBC, Dalhousie University and the Geological Survey of Canada.

The researchers will deploy seismometers along the ocean floor and then fire airguns. The seismometers will record the sound waves that pass through the rocks beneath the sea floor. Establishing the speed of sound through the rocks and analysing the amplitude of signal that bounces back, says Calvert, will help the researchers to determine what kind of rocks exist up to 20 km beneath the sea bed.

“The objective is to locate more accurately the boundary between the subducting oceanic plate and the overriding continent, which is the surface on which a major earthquake will occur,” says Calvert. “The variation in the amplitude of the sound waves which return to the surface should help us to identify regions where the boundary is more firmly locked together - which would be the site of a more extensive earthquake.”

The researchers will use the information they glean to model the forces acting on these boundaries and determine how those forces might be released in an earthquake.

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