Geologists in New Zealand may have discovered how tectonic plates move after detonating half a tonne of explosives on the the country’s North Island.
Explosive slurry was used to fill 12 steel-encased 50m deep holes dug in a line parallel to the border of the Pacific and Australian plates over a distance of nearly 100km across the island.
The seismic shock waves caused by detonation of the explosives, which could be heard up to 10km away, reflected back to the surface off the base of the tectonic plate where they were recorded by more than 1,000 Seismometers.
By decoding the information contained within the seismic waves, the researchers were able to produce a high-resolution image of the layer beneath the earth’s surface. This image showed a narrow, less than 10km thick, lubricating layer of low viscosity “ponded partial melts or volatiles” about 73km deep, over which the tectonic plate slid a few centimetres each year.
The research is published in the latest issue of the scientific journal Nature.
