A new report concludes the coastal town of Kaikoura could be badly flooded if there is a rockslide in the large off-shore Kaikoura Canyon.
The Canterbury Regional Council says the first phase of the canyon study has identified areas of sediment around its rim that could fail during an earthquake.
The study, carried out in partnership with NIWA and Canterbury University, looks at the risk of tsunamis generated by landslides from the unstable sea floor at the top of the Kaikoura Canyon.
It does not include any modelling of new landslide-tsunami events, which will happen in the next two phases of the research due for completion later this year and in 2015.
Project leader Joshu Mountjoy says if a tsunami is triggered in the Kaikoura Canyon, there would be only minutes to get to higher ground.
Dr Mountjoy says people need to be aware of the possibility and, once modelling is done, authorities will have more idea of the level of risk.
The study also shows significant coastal inundation and flooding in parts of Kaikoura would occur if a large South American quake sets off a tsunami, although such a tsunami would take several hours to reach New Zealand.