Major South American earthquake could flood Christchurch suburbs - report

If a large earthquake strikes Peru in South America, it could result in major flooding across Christchurch, which will worsen with higher sea level scenarios, a new report suggests.

New computer modelling has painted a clearer picture, suggesting what Christchurch coastlines could see from a large, distant source tsunami.

The report, by the National Institute of Water and Atmospheric Research (NIWA), says two scenarios; either a one in 500 year 9.28 magnitude earthquake, or a one in 2500 year magnitude 9.49 quake in Peru, would result in major flooding in Christchurch.

"Such large tsunami events are expected to cause severe erosion to the dunes on the coastal strip and at the mouth of the Waimakariri River and the Avon-Heathcote Estuary," the report says.

Scientists say this erosion could cause increased inundation by removing dunes and opening river and estuary mouths.

The modelling suggests the extent of flooding was similar for both tsunami scenarios.

Christchurch City Council head of Civil Defence and emergency management Rob Orchard said it would update information on tsunami evacuation zones one more was learned.

"Modelling like this is so important in allowing us to understand how tsunamis flood land," he said in a statement.

"In turn, it allows us to make the best-informed emergency management decisions."

Experts also warn every part of the New Zealand coastline could potentially be affected by a tsunami.