New research into the country's tsunami risk says more investment in warning systems and evacuation plans is needed to save lives in the event of a major inundation.
The Earthquake Commission asked the New Zealand Institute of Economic Research to analyse the likelihood of a tsunami and the country's capability to manage it.
Using percentiles, it estimated that a one-in-500 year tsunami could kill 17,000 people, injure a further 15,000 and cause $28 billion in damage.
The report said there was a "significant opportunity" to reduce the risk cost-effectively by improving warning systems and evacuation plans, as well as strengthening critical infrastructure.
The report recommended business cases be developed before investment decisions were made.
"In order to reduce mortality risk alone, it could be cost effective for New Zealand to invest an additional $50 million per annum in tsunami mitigation," the report said.
It said New Zealanders had a comparatively high annual fatality risk from tsunami, but the country spent "relatively little on mitigation".
The report said quick fixes could include hardening critical infrastructure and designated evacuation buildings.
Longer-term mitigation solutions included land use planning, the completion of inundation mapping, improved emergency preparedness, evacuation towers and strengthening the Building Code for high tsunami risk zones.
It said tsunamis generated from a regional source - such as from the Kermadec Trench - were the most difficult to prepare for because no ground shaking would be felt.