Quick Dips

Moving Along

Spaced out along the road between Christchurch and Hokitika are fifteen satellite receivers. By taking fixes on their positions relative to each other, they show how the countryside is deforming around the Alpine Fault, and in particular whether the deformation is spread over a relatively wide area or compressed into a narrow band.

If the latter is the case, there is a much greater chance of a major earthquake. "As yet we don't know the likelihood of earthquakes associated with the Alpine Fault," says Professor Dick Walcott of Victoria University, whose study aims to determine whether forces are accumulating towards a big quake or are being dispersed over a broader zone with relatively infrequent, smaller quakes.

The Australian and Pacific tectonic plates, moving rapidly past each other at about 5 cm per year, meet at the fault, which is the only major plate boundary not yet investigated. The measurements will fill in a major gap in tectonic research, and scientists will be watching the results with interest, to see if they correspond with the movements predicted by calculations based on data from other plate boundaries.