Scientists Push For New Research On Alpine Fault

MEDIA RELEASE from GNS Science
27 March 2009

Scientists Push For Major New Research On Alpine Fault

A group of New Zealand and international scientists has proposed a comprehensive plan for a long-term research project to better understand the South Island's largest and most dangerous fault - the Alpine Fault.

They are proposing a range of geological and geophysical research that will eventually include a deep drill hole in the fault that will penetrate the zone where earthquake processes occur.

The project, which will involve scientists from many organisations in several countries, will be a landmark in New Zealand in terms of its scale and for the potential significance of its findings.

The idea for the project was developed this week by 65 scentists from seven countries at a five-day workshop at Franz Josef on the West Coast. The event was organised by geoscientists John Townend of Victoria University of Wellington and Rupert Sutherland of GNS Science, with financial support from the International Continental Scientific Drilling Program.

The Alpine Fault, which is visible from space, extends for more than 650km from south of Fiordland along the spine of the Southern Alps and into Marlborough. Geological evidence suggests it ruptures every 200 to 400 years producing earthquakes of about magnitude 8 that cause strong ground shaking throughout much of the South Island.

Scientists believe it last ruptured in 1717 in an earthquake that produced about 8m of horizontal movement along the fault. In between major ruptures, the fault is locked and produces few significant earthquakes.

Dr Townend said the Alpine Fault had a number of unique geological features that made it an outstanding target for an international research programme.

"The project we are proposing will build on decades of work by New Zealand researchers. We will adress some very specific questions about the pressure and temperature conditions under which earthquakes occur, the role of underground fluids, how large faults evolve, and the mechanisms by which plate tectonic motions take place in the Earth's crust."

Dr Sutherland said a sustained programme of research on the Alpine Fault would help to answer some of he big questions in earth science and, more particularly, how large faults evolve and the type of earthquakes they produce.

"Advances in technology mean the time is right to probe the Alpine Fault with a range of techniques that will compliment each other to substantially improve our understanding of large faults."

The programme will start with a series of surface studies along the Alpine Fault to improve the understanding of its structure and geometry. This will be followed by one or more drill holes that will penetrate the fault zone with the aim of retrieving unweathered rock samples and measuring temperatures and the flow of fluid at depth.

Dr Townend said drill hole rock samples would be analysed in a laboratory so scientists could understand the conditions they had been subjected to and how they deformed.

"Understanding the type of rocks that earthquakes orginate in and propagate through will give us a better insight into the strength of ground-shaking that people will experience when an earthquake occurs on the Alpine Fault. "We're also interested in the broader question of how large faults work. Knowledge gained through this project will have application to major faults throughout the world." Scientists who attended the workshop will prepare funding applications during the next few months and surface studies are expected to start this coming summer.

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