Scientists planning to drill New Zealand fault line to unlock earthquake secrets

An international group of scientists is planning to drill a 1.3-km deep hole into the hills of New Zealand's Southern Alps in order to understand how earthquakes are produced.

The site on the Alpine Fault between the Australian and Pacific tectonic plates is considered one of the best places in the world to study the inner workings of a major plate boundary fault, according to New Zealand's Institute of Geological and Nuclear Sciences (GNS Science).

The scientists from more than a dozen organizations in New Zealand, Canada, France, Germany, Japan, Britain and the United States would examine rock samples from the hole and install sensitive monitoring equipment to record small quakes and measure temperature, pressure and chemical conditions.

Project co-leader Rupert Sutherland, of GNS Science, said the Alpine Fault, which is visible from space, extends for about 650 km and ruptures on average every 330 years, producing earthquakes of about magnitude 8.

"The Alpine Fault saves up all its energy for one big showdown every few hundred years. In between its big ruptures, it stays locked and produces minor earthquakes and tremors," Sutherland said in a statement Tuesday.

Scientists believe it last ruptured in 1717 in an earthquake that produced about 8 meters of horizontal movement and vertical movement of up to 2 meters.

Other projects had drilled into plate boundary faults after large earthquakes, but this would be one of the first attempts to probe the inside of a major fault before it ruptured, he said.

A smaller group of scientists drilled two boreholes to about 150 meters into the fault in 2011 and found a finely-ground impermeable layer of rock in the center of the fault zone, holding back large amounts of fluid on the upper east side.

Scientists believed the large difference in fluid pressures on either side of the fault zone could play a role in initiating the first slipping movements as an earthquake begins.

By comparing rocks retrieved by drilling with rocks exposed at the surface, the researchers hope to discover how the Earth's crust deformed during earthquakes and learn about chemical and physical changes at various depths inside the fault zone.