Reflections on the Boxing Day Tsunami

To say that the Boxing Day Tsunami had a huge impact is an understatement. It affected the world, the science community and me. My science training had not prepared me for the sheer devastation the earthquake and tsunami did across 19 countries. New Zealand was not immune to the devastation either; we lost seven kiwis that day. The total loss of life and damage is beyond comprehension. Today I reflect on the lessons we have learned as a science community to help ensure the loss of life and damage does not occur on that massive scale again.

What we couldn’t appreciate at the time was the Boxing Day tsunami was the start of a decade of deadly and destructive tsunami. These include the 2007 Solomon Islands (Gizo), 2009 Samoan Islands, 2010 Chilean, 2013 Solomon Islands (Temotu) Tsunami and, the largest of all in the Pacific, the 2011 Japan tsunami. All these events demonstrated the massive power of the mega-earthquakes which hugely displace the sea floor and sea water above causing tsunami.

So what have we learned in this decade of tsunami? Globally, we learned that we needed a much better tsunami warning capability. Before the 2004 Boxing Day tsunami, the Pacific Tsunami Warning and Mitigation System (PTWS) was the only tsunami warning system on the planet, but it is now one of four globally covering the world’s oceans. So at least we have learned that lesson.

In New Zealand, we have changed our tsunami warning system considerably. We now use tsunami forecast models to establish the potential threat in pre-defined coastal zones and issue this information in map and text formats. The threat levels can be used to inform evacuation decisions based on planned evacuation zones and routes. GNS Science act as the science advisors to the Ministry of Civil Defense and Emergency Management (MCDEM) employing forecast models and the expert knowledge of the “Tsunami Experts Panel”, a group of New Zealand based tsunami scientists.  

We also updated the science and technology in the wider Pacific; on 1 October this year PTWS improved its tsunami warning capability using similar techniques to those we currently employ in New Zealand. Now the Pacific Tsunami Warning Centre in Hawaii (the operational centre of PTWS) sends pictorial and text messages to member countries based on tsunami forecast models and the expected impacts on coastlines. This replaces the messaging based solely of the size and location of possible tsunami-generating earthquakes.

We have done a lot of work in the last decade. But here is what keeps me awake at night: we still rely totally on natural warnings (feeling high levels of, or long lasting shaking, and unusual sea behaviour) for local-source tsunami warning. These are the tsunami caused by earthquakes or triggered undersea landslides near our coast.  And there are some situations in New Zealand where a tsunami-causing earthquake may not be felt strongly, leaving a potential gap in our tsunami warning strategy. On the east coast of the North Island we have a huge fault (the subduction zone) where the Pacific tectonic plate meets and is pushed down below the Australian plate. This is similar to the tectonic situation off the coast of Japan. Many earthquake types can happen in this process, including “slow” earthquake which will not be strongly felt. And further north of New Zealand, a very large earthquake could send a tsunami towards cities and townships of the upper North Island without high levels of shaking being felt on-land (see 2013 GNS Science tsunami hazard update). Two “slow”earthquakes in 1947 caused tsunami which deposited seaweed in power line and damaged buildings, but thankfully caused no loss of life, in small communities north of Gisborne.

Work continues on the science and technology necessary to provide official warnings for these local events for New Zealand, which may provide minutes to 10s of minutes of warning. Watch this space!

I realise this sounds very “doomsday” scenario. And we haven’t been affected by a tsunami like this for a long time. But I’d like to see a local-source tsunami warning capability piloted here in New Zealand. I’m a realist and know the amount of resources required to make this happen.  But the Boxing Day tsunami taught me that the seemingly impossible can happen. We are more ready than we were in 2004. But we need to be even more ready than we currently are.

The most fundamental lesson we’ve learned though isn’t about science. It’s that people’s direct actions matter. The day may come when we have all the scientific systems set up, but we will always need to rely on ourselves and each other. If you feel a long or strong earthquake on the coast, evacuate immediately. Here is the best advice about evacuating during a tsunami (from the MCDEM):

·         Take your getaway kit with you if possible. Do not travel into the areas at risk to get your kit or belongings.

·         Take your pets with you if you can do so safely.

·         Move immediately to the nearest higher ground, or as far inland as you can. If evacuation maps are present, follow the routes shown.

·         Walk or bike if possible and drive only if essential. If driving, keep going once you are well outside the evacuation zone to allow room for others behind you.

·         If you cannot escape the tsunami, go to an upper storey of a sturdy building or climb onto a roof or up a tree, or grab a floating object and hang on until help arrives.

·         Boats are usually safer in water deeper than 20 metres than if they are on the shore. Move boats out to sea only if there is time and it is safe to do so.

·         Never go to the shore to watch for a tsunami. Stay away from at-risk areas until the official all-clear is given.

·         Listen to your local radio stations as emergency management officials will be broadcasting the most appropriate advice for your community and situation.