A new report warns a 7.5 magnitude Wellington earthquake would cause a $16 billion hit to New Zealand's economy if the region's infrastructure isn't improved.
The quake would cause damage to key infrastructure that could take years to fix and see mass emigration by both people and businesses.
But it finds a coordinated investment of $3.9 billion would save the nation $6 billion in the aftermath.
The Wellington Lifelines' regional resilience project was set up to study Wellington's vulnerability to a major earthquake - and it says it is just a matter before "the big one" occurs.
The study says the region needs to improve its infrastructure resilience "to minimise the potentially devastating impact of a disaster in Wellington".
"We know that the big one is 'when' not 'if' and that quakes in the past few years have been quite mild compared with this scenario," says Dame Fran Wilde, chair of the group.
"Wellingtonians are reasonably well prepared, but household resilience needs to be supported by functioning infrastructure to maintain the liveability of the city following a major event. We want to galvanise our leaders into action to make sure this happens".
The study sets out a $3.9 billion investment programme across the fuel, transport, electricity, telecommunications, water and gas sectors.
These are known as lifeline utilities - organisations that provide essential infrastructure to the community. Their improvements would be rolled out in three integrated phases over 20 years.
If this is completed before an earthquake hits, the study finds the investment would reduce the economic loss to $10b. It would also help speed up the time to recover and contribute to the survival of the regional economy.
Dame Fran is now asking decision-makers to fund and build them in the sequence suggested.
"Much of the programme is still unfunded and will require commitment and foresight on the part of both owners and consumers in order to secure the economic future and wellbeing of the Wellington community," Dame Fran says.
"This is a challenge for everyone. It may cost consumers more over time, so the question that Wellingtonians and their leaders need to consider is whether it is worthwhile ensuring that there is a viable economy and jobs following a large earthquake."