Invercargill will be a good place to be in the South Island when the alpine fault ruptures.

Though there are expected to be "tens" of injuries in the city, it will be a lot less than many other areas that are closer to the fault line, which runs for about 600km up the spine of the South Island.

Modelling has been carried out to predict the consequences of the alpine fault rupturing and causing a magnitude 8 earthquake.

Historically, there has been a major rupture of the faultline about every 300 years, and the last one was 301 years ago.

"Probably within the next 75 years the alpine fault is going to do its thing," Alpine Fault Magnitude 8 [AF8] programme manager Jon Mitchell said.

"Because Invercargill is some distance from the alpine fault it's a better place to be."

However, unreinforced buildings in the city would be a danger, he said.

Mitchell, who briefed Southland mayors at the Southland Civil Defence Emergency Management Group meeting in Invercargill on Thursday, is driving the development of the South Island alpine fault earthquake response.

The mission was to immediately mobilise a co-ordinated response across the South Island to meet the community's needs and minimise the loss of life, Mitchell said.

The project is nearing the end of its second year, with Mitchell outlining a draft plan for the multi agency and South Island-wide response effort.

For Invercargill and most of Southland the direct disruption and damage would be low, but Fiordland would be substantially damaged, he said.

Southland's role would be to support other parts of the South Island and receive evacuees from areas including Queenstown Lakes.

The deaths and injuries in Queenstown would be challenging for authorities but the real issue would be getting access to get people out, he said.

The West Coast was most vulnerable to serious damage.

Following the main earthquake, there would be many more aftershocks, ongoing failures of structures, hundreds of thousands of landslides, damaged roads making it difficult for people to move around, and many people seeking emergency accommodation.

Mitchell said the response plan would be adopted in June.