Scientists eye drilling alpine fault

International scientists have descended on the West Coast to discuss a plan to drill several kilometres into the Alpine Fault in a bid to learn more about earthquakes.

The project, touted as first of its kind in New Zealand, should provide an important insight into how big earthquake faults evolve, and generate quakes.

From Sunday, 60 scientists from seven countries will gather at Franz Josef Glacier for a five-day workshop, and develop a drilling plan.

Project leader John Townend, of Victoria University in Wellington, said lowering instruments into the heart of the Alpine Fault would enable scientists to investigate processes not normally accessible.

Measurements would include pressure, temperature, rock fracturing, and the chemistry of fluids, rocks and gases.

Dr Townend said a large earthquake on the Alpine Fault could strike this century.

He said there was a compelling case to install instruments at depth to better understand and monitor the South Island's most dangerous fault.

As well as penetrating the earthquake zone and extracting rocks for analysis, scientists hoped to install underground instruments that may shed light on the timing and severity of quakes.

The rocks from most major boundary faults around the world lie deep underground, largely beyond the reach of present drilling technology, but on the West Coast they are much closer to the surface.

Monitoring equipment had been successfully installed deep inside major faults in several countries including Japan, Taiwan, and the United States.

Scientists who led the San Andreas Fault deep-drilling project in the US will attend the Franz Josef workshop to share their knowledge.

The Alpine Fault extends for more than 650km from south of Fiordland, through Milford Sound, and along the spine of the South Island into Marlborough, right through the heart of Franz Josef Glacier village.

According to Geological and Nuclear Sciences (GNS), it is one of the world's major active faults and is visible from space.

Geological evidence suggested it ruptured every 200 to 400 years, producing earthquakes of about magnitude 8.

Scientists believe it last ruptured in 1717.

It formed part of the boundary between the Pacific and Australian tectonic plates, which are moving past each other and colliding, forcing up the Southern Alps.

The fault moves at a rate of about 25m every 1000 years, which is fast by global standards. In between its major ruptures, it is "locked" and produces few sizeable earthquakes.

- NZPA