MEDIA RELEASE

19 September 2006

Listening to the Alpine Fault

Understanding why one part of New Zealand’s Alpine Fault has so few earthquakes compared to elsewhere on the fault is the focus of a research project at Victoria University.

Recently, nine seismographs were installed between Fox Glacier and Harihari, from the lowlands to elevations up to 1200m in the Southern Alps. They will record ground motion over the next six months including many small earthquakes below the threshold of human perception.

The Alpine Fault is a major fault that runs along the foothills of the Southern Alps and extends for over 400 km from Fiordland to Marlborough.

Principal investigator, Bronwyn O'Keefe, who will analyse the results for her MSc in Geophysics, says the survey is part of an investigation of the central section of the Alpine Fault where there are significantly fewer earthquakes than in the north or south.

“While the Alpine Fault is associated with large earthquake events, we don’t fully understand the relationship between small earthquakes and the large events that are thought to occur every 300 years or so.

“The investigation will locate the many small earthquakes that occur over the survey period, see what depths they are occurring at and identify if the Alpine Fault or surrounding minor faults are causing them.”

Ms O’Keefe says it is hoped the denser network of recording instruments than the national network provides will lead to a better understanding of the fault.

The survey team will be returning to the West Coast in early November to collect data and check the equipment. Retrieval of instrumentation is expected to be in late February or early March.

ENDS