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Getting better prepared for the threat of tsunamis

Our tsunami scientists have developed a database of more than 700 tsunami scenarios and maps that can be used for tsunami warning purposes for New Zealand. The database consists of modelled seafloor earthquakes in subduction zones right around the Pacific Rim capable of producing a tsunami of one metre or greater at the New Zealand coast.

Tsunami safe zone road marking. Photo: John Callan

The core message in tsunami workshops: Long or strong, get gone. Photo: John Callan

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“The tsunami scenarios and maps GNS Science has developed will help us to provide timely information when large earthquakes occur to those who live, work in or visit New Zealand to help them keep themselves and their families safe.”

Sarah Stuart-Black, Executive Director, Ministry of Civil Defence and Emergency Management

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Pre-calculated scenarios are not new, but in the past year we have more than doubled their number and added more detail, so they are more useful to responding agencies. 

When an earthquake occurs in a subduction zone around the Pacific, the nearest scenario in the database can be called up to provide an early estimate of the height of a tsunami and arrival time at the New Zealand coast. As more detail on the size, depth, location and mechanism of an earthquake becomes available, the initial estimate can be refined to provide a more accurate threat assessment of an incoming tsunami. 

There are 43 zones for each scenario around the entire New Zealand coast, with each zone potentially having a distinct threat level for a particular tsunami. We will continue expanding the number of modelled scenarios in the database, so it covers a greater range of earthquake possibilities and tsunami sizes. 

Aligned with this work, the ‘Quicker and safer tsunami evacuations through agent-based modelling’ project has been involved in public workshops in Napier, Petone, and Sumner to help improve tsunami evacuation planning for communities. The workshops show computer simulations of the movement of people during evacuations and encourage feedback from the public. 

The project encourages people to familiarise themselves with evacuation routes they would use in the event of a tsunami. Walking or cycling their preferred route will help to identify any potential obstacles along the way. 

A core message in these workshops is ‘Long or strong — get gone’. If people feel a strong quake that makes it hard to stand up, or a weak rolling earthquake that lasts a minute or more, they should move immediately to the nearest high ground, or as far inland as they can. They should walk or bike if possible. Don’t wait for official warnings.