Wellington would have to rely on ships and helicopters to bring in help in the event of a serious earthquake.
Specialists in disaster management who met in the capital on Wednesday say the city would be left largely isolated in the event of such a quake.
GNS social scientist Kim Wright says Wellington is not like Christchurch, which has many routes out of the city. She says transport routes would be badly damaged, the airport left inoperable by liquefaction and fires could start if gas lines rupture.
GNS estimates that as many as 138,000 people would need emergency accommodation. Civil Defence has identified 60 welfare centres it could use in such a disaster.
Its controller says the emergency plan is sound, but will be looked at again in light of the Christchurch quake.