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Wednesday, July 30, 2008

Put aside anthropogenic climate change; human action can trigger any number of natural disasters, including earthquakes.

Tremors in the crust beneath the North Sea have become more frequent since oil drilling operations began there, and mining operations are also known to increase the frequency of tremors.

Both drilling and mining redistribute the normal stresses present in rocks, but they are not the biggest cause of man-made earthquakes.

"Dams are the most dangerous man-made structure likely to cause quake," says David Booth of the British Geological Survey.

By artificially holding a large volume of water in one place, dams increase pressure on fractures beneath the surface of the earth. What's more, water has a lubricating effect, making it easier for the fractures – or faults – to slip.