Alpine Fault drilling starts in three months

SARAH-JANE O'CONNOR
Last updated 10:01 25/06/2014
Alpine Fault

ALPINE FAULT: In early October, a New Zealand-led team of scientists will begin drilling a 1.3 kilometre deep hole near Whataroa, north of Franz Josef.

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Scientists will drill 1.3km into the Alpine Fault to get a better understanding of the fault and the earthquakes it produces.

In early October, a New Zealand-led team of scientists will begin drilling a 1.3 kilometre deep hole near Whataroa, north of Franz Josef.

The borehole will allow the scientists to install monitoring equipment to record small earthquakes, temperature, pressure and chemical conditions.

Led by GNS Science, Victoria University and the University of Otago, the project includes organisations from Canada, France, Germany, Japan, the United Kingdom and the United States.

The on-land boundary between the Pacific and Australian tectonic plates, the Alpine Fault ruptures on average every 330 years causing earthquakes of about magnitude 8.

Scientists believe the fault last ruptured in 1717 and has a 28 per cent probability of rupturing within the next 50 years.

GNS Science tectonic geologist Dr Rupert Sutherland said the fault "saves up all its energy for one big showdown every few hundred years".

He said it represented a major hazard to the South Island and drilling technology could gain crucial information about the "fault's inner workings".

In early 2011 two boreholes about 150 metres deep were drilled into the fault near Whataroa. Scientists were surprised to find a finely-ground impermeable layer of rock in the centre of the fault zone which held back large amounts of fluid on one side of the fault.

Large differences in fluid pressure on either side of the fault zone could play a role in initiating the first slipping movements as an earthquake began.

In the past projects have drilled into plate boundary faults after large earthquakes, but the West Coast study will be one of the first attempts to probe the inside of a major fault before it ruptures.

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- The Press

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