Research has found a large earthquake on the Alpine Fault would produce much more intense shaking than previously thought.
Researchers from the University of Canterbury carried out highly detailed simulations of an earthquake of a magnitude 8 or more.
They said there was a 30 percent chance of a rupture along the Alpine Fault in the next 50 years, and the research had been conducted partly for the purposes of emergency management planning.
Professor Brendon Bradley said one of the key findings from the year-long study, was how the location of the fault break affected the intensity of the ground movement.
"The shaking in the Canterbury and northern half of the South Island is stronger than what we would have previously predicted and in the southern and south-eastern parts of the South Island it's weaker than what we would have previously predicted."