WREMO’s position on tsunami sirens

WREMO, the Ministry of Civil Defence & Emergency Management, GNS Science and New Zealand’s Tsunami Working Group all agree with international best practice – that tsunami sirens are inappropriate as a warning system in regions subject to local sourced tsunami.

The time it takes for scientists to determine whether an earthquake has created a tsunami threat and then send out official warnings can be longer than the time it takes for a local source tsunami to reach the coast. A tsunami could arrive in as little as 10 minutes.

International research (especially from Japan) also shows that the existence of sirens creates a false sense of comfort with the public in that they expect to be warned by the siren, rather than making a decision to respond to the earthquake itself. If you felt a big earthquake and the siren didn’t sound, what would happen to you?

The earthquake damage itself can make the sirens fail – in a survey after the 2011 earthquake and tsunami in Japan, 17 out of 27 affected municipalities responded that their tsunami alert transmission system failed from power cuts or earthquake damage and did not function properly at the time of the disaster.

In other cases, sirens have led to people ignoring them or delaying evacuation due to false alarms. This is especially true in places where the sirens are triggered automatically without a human decision.

There are also problems with the effectiveness of the sirens through audibility (especially with Wellington’s wind, whether you are indoors or outside), which we hear about every time the sirens are tested around the country.  If you didn’t hear it but thought you should, you might not evacuate.

So, for areas where a tsunami caused by a large local earthquake is the biggest tsunami threat, the use of fixed coastal sirens for tsunami warning is not only not advised, it can be dangerous to have them.

Lower Hutt has sirens which were installed in the 1970’s for flood warnings, not tsunamis – there are sirens in Manor Park and Wainuiomata, which are not in any tsunami evacuation zone.  If these sirens are activated, they tell you that something is happening or going to happen, or has happened and that you should listen to the radio and seek further information - wremo.nz, or on social media. They won't be used for tsunami in the future.

Don’t rely on others to tell you want to do. The best and most reliable warning system for local source tsunami in New Zealand is the natural warning itself – the ground shaking for longer than a minute, or so strong that it’s hard to stand up.  It doesn’t require power, or a smartphone, it just needs you to react to mother nature’s blunt and obvious warning and immediately evacuate.

 

References:

Technical Standard [TS03/14] Tsunami Warning Sirens.  July 2014 ISBN 978-0-478-43502-3 Published by the Ministry of Civil Defence & Emergency Management

http://www.civildefence.govt.nz/assets/Uploads/publications/Tsunami-Warning-Sirens-TS-03-14.pdf

http://www.iddri.org/Publications/Disaster-Evacuation-from-Japan-s-2011-Tsunami-Disaster-and-the-Fukushima-Nuclear-Accident