You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
The increase is a result of computer modelling by GNS Science and the National Institute of Water and Atmospheric Research, which shows flooding could reach further inland than previously thought.
The modelling shows what would happen in the event of a tsunami generated by offshore earthquakes greater than magnitude 9 in areas like South and Central America.
As a result, the city council will add tsunami risks to 7394 Land Information Memorandums or property records.
Tsunami evacuation zones are areas people should evacuate as a precaution, rather than tsunami hazard zones, tsunami risk zones or tsunami inundation zones.
About 12,600 households will be added to the existing orange and yellow tsunami evacuation zones, which now includes a total of about 23,300 properties.
In the event of a long or strong earthquake, residents in red or orange evacuation zones are advised to head immediately to the nearest high ground or inland.
The same is advised if they are instructed by Civil Defence, or if they hear tsunami sirens.
The yellow evacuation zone may flood in a tsunami event and people should evacuate if told to do so.
People in areas outside the tsunami evacuation zones may not be advised to evacuate in a long or strong earthquake.
An evacuation zone review for Banks Peninsula will be done after the computer modelling is completed.