If a large earthquake hit near Wellington, a tsunami could reach the central city within just 10 minutes, modelling shows.
The concerning figure makes it all the more important for locals to know their fastest route to safety - something which they can learn with a new, educational phone app that has been released for the region.
The app, named Tsunami Ready, is a pro-bono project from digital agency Alphero, and will be trialled in Wellington before hopefully being rolled out nationwide.
"People have a general impression that somebody will tell them what to do," said Alphero chief executive Caroline Dewe.
Many Kiwis knew what to do in an earthquake, but mistakenly believed they would receive an official warning from the Government if they needed to move to higher ground, she said.
But tsunami data from the Wellington Region Emergency Management Office (WREMO) showed the earliest a tsunami could reach the region was within just eight minutes of a big earthquake.
The likelihood of people receiving an official warning before then was low. There was also the possibility networks could be down and sirens might not work.
"You can't rely on infrastructure being up ... as soon as it stops shaking you need to get up and go immediately."
There were also no tsunami sirens in Wellington, Dewe said.
The app educates users on tsunami risks and safe zones, and helps them map the quickest route to a safe zone.
Users are encouraged to learn and practise the route beforehand so they are comfortable with it and do not need to resort to using the app in a time of high stress.
They are also encouraged to walk, run or cycle to a safe zone if possible, to avoid getting stuck in traffic and to keep the roads clear for people who have less mobility.
The app would also help people realise just how far they needed to go to be safe.
They might have an impression they needed to head to the top of the highest hills in the city, but in reality might only need to walk a few blocks to be safe.
Dewe hoped if the app was successful in Wellington they might be able to secure national funding to roll it out across the country.
WREMO regional manager Jeremy Holmes said the app was a "fantastic initiative" and was "really important to the people of Wellington".
A severe 8.2 earthquake in 1855 created a tsunami in the city that moved around the harbour like water in a fishbowl, with waves moving from "side to side", he said.
It showed that another large quake with a locally-sourced tsunami could cause a similar effect and have an "enduring" impact, as it likely wouldn't be just one wave.
"It is likely to cause quite devastating impacts on the region," he said.
"1855 was sort of the largest one that we've had within the region for quite some time ... we know we're due for some sort of similar type event."
The recent earthquake and tsunami warnings around the country earlier this month highlighted the risks, and the fact that tsunami warnings could sometimes last for hours.
Holmes reminded people if the earthquake was long or strong they needed to immediately get to higher ground.
The app is currently available on Apple apps and is pending approval for Android. More information can be found on the website tsunamiready.co.nz.