Research on the Alpine Fault by a team of scientists has revealed it is moving faster than first thought.
The South Island fault is moving at up to 27 millimetres a year in some areas, and an average of 13mm a year.
The work, at Inchbonnie, 60 kilometres from Greymouth, is being funded by the Foundation for Research, Science and Technology.
One of the team, Pilar Villamor, says testing the speed of the faultline at different interval has helped to establish that the southern regions are more at risk.
She says the research has also shown major earthquakes on the Alpine fault are likely to occur only about once every 300 years, not every 150 to 200 years as previously thought.
The last big rupture on the faultline was in 1717, causing an earthquake of magnitude 8.