A 7.5 magnitude quake on the Wellington fault would cost New Zealand more than $16 billion in lost economic activity, unless the region's infrastructure is improved, a new report says.
The report, by the Wellington Lifelines Group, said the cost would be in lost economic activity alone - without counting the social or recovery cost or building damage.
Electricity and other supplies could be "out for months" if the region doesn't continue - or hasten - the investment, group chair Dame Fran Wilde said.
A 20-year investment programme, costing about $3b, to get services to the point where they stay operating or recover sooner, would reduce the economic loss to about $10b, the report estimates. Some of this was already underway but much was unfunded.
It would put the regional - and national - economy on a much better footing, Dame Fran said.
The critical feature was is that work had to be done in the correct sequence. "There's little benefit, for example, in having a highly resilient water network if electricity isn't available for the water pumping station," she told Morning Report.
The investment would also help build confidence in Wellington, where the issue of insurance premiums is of growing concern.
"We know that this government is very committed to infrastructure improvement, and so we're hoping that they will look on Wellington as an essential case, if you want, and we know from Christchurch that when we do put in resilience prior to the event, it is it has a much better outcome."
But there was definitely not a case for moving the capital, she said.
"Where would you move it to? An active volcano field in Auckland? The Alpine Fault in the South Island? All of New Zealand is at risk from some kind of natural disaster and we need to start planning for it and thinking about it well in advance."
The Lifelines Group is made up of the Wellington regions' councils, the area's power, water, rail, road and port companies, Wellington airport and GNS.