Tsunami risk all too real on Shaky Isles
New Zealand is not dealing with the tsunami threat well, as Anne French explains.
When the magnitude 7.8 earthquake struck the country a fortnight ago, it brought with it a high risk of tsunami on the eastern coasts of both islands.
In New Brighton, it was two hours before the tsunami sirens were activated. In Napier, the tsunami sirens weren’t used at all because, as the chief executive of the Napier City Council put it, ‘‘that would have caused mass panic and evacuation’’. Elsewhere there was a lot of confusion. Is this good enough? No. When you look at the danger that a tsunami represents, doing nothing is reprehensible.
People caught up in a tsunami can suffer horrendous injuries and the death toll is high, especially among the elderly and the very young – essentially, everyone who can’t run away.
In the past few years, tsunami in other countries have been in the news. No one who saw the news footage of the 2011 Tohoku tsunami in Japan can forget the giant waves caused by the massive magnitude 9.0 earthquake.
The wave was 40-metres high in Miyako City and travelled 10km inland in Sendai. An area measuring 560 square kilometres was flooded – that’s about 20km by 20km.
It’s tempting to think such things can’t happen here. The signatures of past tsunami in New Zealand are subtle, hard to read except by the expert eye.
The first big tsunami in New Zealand to strike since European settlement began was back in 1855. About 20 minutes after the magnitude 8.2 Wairarapa earthquake, a 3 to 4m wave came into Wellington Harbour via the harbour entrance and over the shallow isthmus where the airport is now.
It bounced off the Petone foreshore and was 2m deep on Lambton Quay.
In 1931, the Napier earthquake triggered a 3m tsunami that struck Napier city. In 1947, a magnitude 7.0 quake near Poverty Bay created a tsunami that struck the coast just north of Muriwai and affected the coast up to Tolaga Bay. It peaked at 10m high, at Turihaua.
Tsunami aren’t someone else’s problem. They are New Zealand’s problem, and right now we aren’t dealing with them very well.
The airline industry, for instance, takes safety extremely seriously. People won’t entrust their lives to aeroplanes unless they know them to be safe. So the industry learns everything it can about what can go wrong.
It looks into near misses just as closely as into accidents. If you watched the film Sully, which screened recently, you will have a sense of how thorough the investigation is, even into an incident in which no lives were lost. Critically, aviation safety depends on an understanding of the whole system.
To think about how we can manage our tsunami risk better, let’s look at the tsunami system in Japan.
About 20 per cent of the world’s big earthquakes happen there, so the Japanese have had lots of practice. The first written earthquake records date back to 599AD. Everyone understands earthquakes, tsunami and the damage they do.
Experiencing a big earthquake or a tsunami equips the survivors with knowledge and skills that will help them survive a later event, but the Japanese know that such visceral memories can’t be passed on to the next generation.
If hazardous events skip a generation, precious knowledge is lost. That’s why they place markers on mountains saying, ‘‘The tsunami of Year XYZ reached this point’’. When the ground moves and people start running, they know how far to run.
If people are in the city with no high place to run to, they can climb stairs up the outside of buildings and take refuge on the roof. They are called evacuation buildings and in the 2011 Tohuku tsunami they saved around 5000 lives. The Japanese are also big on early-warning systems. They have a large sensor network and as soon as the sensors detect the first tremor, a public warning is generated on news media, with text alerts to mobile phones, and people take action.
If there’s a tsunami warning, people know to start evacuating. The problem arises when, for whatever reason, the warning doesn’t sound.
The 2011 Tohoku earthquake provides a kind of natural experiment. At first, the sensors underestimated the earthquake’s magnitude. It was, after all, unprecedentedly big. By the time they recalculated, the electricity had gone off and they couldn’t issue the warning. The first tsunami waves began to arrive less than an hour after the first tremors.
Thousands of people in the tsunami zone waited for a warning that never came, and died.
There were 15,891 confirmed deaths, most from drowning. A further 2500 people are still reported as missing, and 6152 people were injured. But many thousands of people who felt the tremors and ran for their lives, without waiting for the official alert, are still alive. From that we can conclude that taking matters into your own hands saves lives and that warning systems are subject to failure, and can kill.
The Japanese also place great weight on investigating the response to earthquakes and understanding what worked and what didn’t. They set up their first earthquake investigation commission in 1892. It was superseded in 1925 by the Earthquake Research Institute.
When we look at what happened last week in New Zealand, we should think about the elements of a good system. What do we have in place already? What do we lack? What do we have that’s not working? Who makes the call? Are they the right people? What do we need to do differently or better?
A sober investigation by an independent expert of our tsunami management system, and implementation of the findings, will save lives the next time the ground starts shaking.
Anne French is an associate of the New Zealand Institute of Economic Research.