Keith Rankin Essay – Friday’s Tsunami Messaging: Why Not Tauranga and Auckland?

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Essay by Keith Rankin.

Keith Rankin.

On Friday at 6am I woke up in Covid Level 3 Auckland to news of a big earthquake around 100km east of East Cape, at about 2:30am. While many people in Auckland had apparently felt it, many more had uninterrupted sleep. Descriptions on Radio New Zealand’s Morning Reportsuggested that this was an earthquake similar to one that I had felt from the Kapiti Coast in 1968; the Inangahua (Buller Gorge) Earthquake. Certainly, it was a quake that suggested danger, but at a sufficient distance for coastal dwellers to evacuate from without panic. Certainly, an earthquake itself is the best message of a possible tsunami. (Though many of the worst tsunamis in natural history did not arise from earthquakes.)

By 7:30am I was eating breakfast in front of The AM Show – as I do – when breaking news came through of an entirely new earthquake, near the Kermadec Islands (of which Raoul Island is the largest). I knew these islands to be 1,000 km to the northeast of the North Island. But I suspect not too many other people knew that, and media coverage of the new event was both slow and confused. Over an hour later, while doing the laundry, I heard about the magnitude 8+ earthquake, also near Raoul Island.

By now I was quite alarmed. The 11 March 2011 earthquakes off northeast Japan were initially reported as magnitude 7 followed by magnitude 8. (The big one off Japan was later upgraded to magnitude 9.) And I think we all remember the carnage created in Japan – ten years ago this week. New Zealand is not immune from such an event, nor is Australia.

The events were enough for the television and radio media to abandon their schedules, giving wall to wall coverage of the tsunami threat, but only focussing on the areas covered by the New Zealand Civil Defence alert. The alert barely changed as a result of the huge Kermadec quakes; quakes which probably nobody on the planet actually felt. The area for evacuation remained basically the same (Matata in the Bay of Plenty, to Tolaga Bay on the East Coast), though a fraction of the Northland east coast was added (with Aupouri Peninsular somewhat later again). And Great Barrier Island. The alerts continued to emphasise the importance of feeling earthquakes as primary civil defence alerts, and continued to give the impression that these three earthquakes were part of a cluster off East Cape. (Indeed, see this report Tsunami warning for Australia following New Zealand earthquake from Nine News in Australia, which shows only the east of East Cape location on its main graphic.)

Still worried this could be a serious event, I looked for information about what people on the Bay of Plenty coast between Great Barrier and Matata should do (and people north of Great Barrier but south of Whangarei). Anybody with Google Maps on their phone should have been locating the Kermadec Islands, and seeing their orientation towards New Zealand. There was no guidance to these people, and all the reporters seems to be at the places that were on the evacuation list. The undermentioned eastern Coromandel and western Bay of Plenty districts look distinctly vulnerable from the Kermadecs. This includes Tauranga, a city of 150,000 people.

Were people in Tauranga evacuating? Don’t know, the New Zealand media phone was off the hook. I saw a man in Tauranga reporting for Al Jazeera, but he was really only relaying news from the New Zealand media; news more focussed on Whatatane and Whangarei. There was no sense that Tauranga itself might be in danger. I did hear – however – that many people in Mangawhai did evacuate, despite their town not being in the notified evacuation zone. And, I hope that the people of Pukehina Beach also evacuated, despite being west of Matata. It would have a long walk to higher ground for those without cars; though Aucklanders with baches there were supposed to be in Auckland.

I looked up the Pacific Warning Centre (based in Hawaii). While there were warnings throughout the south and west Pacific – including South America – the only warnings I saw predicting a wave over one metre high were for New Caledonia and Vanuatu. (The second time I looked, at about 11:30am, New Caledonia had been downgraded.)

Today I did a couple of Google searches to see what the chatter was in Brisbane; after all, a tsunami hitting New Caledonia from Raoul would be expected to continue on to the long Queensland Coast (though a category 5 hurricane – tropical cyclone Niran – was in the way). I found a story – Tsunami Warning Sends People to High Ground in French Polynesia – about people heading for the hills in French Polynesia. And I saw this – The Informer: A tsunami warning, a review and an apology – just another Friday in 2021 – claiming all three earthquakes were at the Kermadec Islands (“our neighbours”), and while there was no threat to Australia a 64cm wave was recorded on Norfolk Island. Looking at the map, Norfolk Island is in the middle of a straight line from Raoul Island to Brisbane (at 23 degrees latitude).

Overall, the Australian coverage seems to have been complacent to the extreme.

For those not on the hills, most of the rest of us – whether at Covid19 emergency level Two, or Three – settled excitedly, to watch the notified government press conference from the Beehive bunker. We love to hear the stage-managed ‘word’ from the top. Then, just as Kiri Allan was starting to speak, Aucklanders got the mobile phone alert. On my phone I press OK to make the noise go away, and the messages disappear as well. Possibly not ideal!? On my partner’s phone, the message remained, so I read it there.

These NZ Herald articles give the general tone: Earthquakes trigger tsunami warning: Government update on threat to coastal New Zealand, and ‘I just want to give her a big hug’: How New Zealand’s tsunami scare unfolded.

Three points to note about the Auckland message. First, it looked like a message mainly for the west coast beaches, such as Piha. That’s the only bit I saw before unintentionally erasing the message. Then, while the message itself only indicated action from those on the beaches or in boats, it gave little guidance about what people not on the beaches or boats should do. Twenty minutes after the alert, relatives living on low ground but not living at a coastal address, turned up – to my surprise – at our front door. It was nice to see them, and certainly the tsunami alert provided socialising opportunities for otherwise locked-down Aucklanders. Apparently, some the roads in suburban Auckland at 11:45am were much busier than normal for a city in pandemic lockdown, despite no evacuation notice given. The third point was that the message ended with a request to ‘pass this message on’. But, even on my partner’s phone, the message could neither be forwarded nor copied and pasted into an email.

I would hate to think of how wrong things would have gone in Auckland and Tauranga had an event on the scale of Samoa in 2009, let alone the scale of Japan in 2011, eventuated. (Further, it was high tide.) If Aucklanders and Taurangans were to face a major tsunami without fatalities, the evacuation should have begun within half an hour of the magnitude 8+ earthquake (ie around 9am, in this instance). (The people on eastern Australia would have had more time – Brisbane is the same distance from the Kermadecs as is French Polynesia.) I do not mention Australia in jest; after all, in 2004 nearly 300 people in Somalia died as a result of the Indonesian tsunami that Boxing Day. Distance is not necessarily a measure of risk. The Kermadec seismic zone is potentially capable of generating similar size waves. Indeed Southeast Queensland faces one-in-five chance of a tsunami in the next 50 years, according to an article published in the Brisbane Courier on 16 November 2017.

Re Auckland, I heard mayor Phil Goff saying that Great Barrier Island (Aotea) is not called ‘Great Barrier’ for nothing, implying that Aotea shelters Auckland from tsunamis. However, this Newshub (21 November 2016) story Mega-tsunami: Would Auckland survive? suggests caution. “One of the great urban myths in Auckland is that the two main islands adjacent to the city would protect most sea-side suburbs and the CBD from significant tsunami damage. Dr Nandasena [tsunami expert] believes Waiheke and Rangitoto could actually amplify tsunami waves coming into Waitemata Harbour.” Presumably this is true of Aotea as well as Waiheke and Rangitoto.

Some context about why the general tone of scientific messages was somewhat unconcerned, came through only towards the end of Friday. In Earthquake swarm: NZ just tasted a ‘regional source’ tsunami: What are they? (NZ Herald, 5 March), Dr Jose Borrero, of Raglan-based marine consultancy eCoast Ltd said “Anything that happens along the Kermadec Trench affects us less and less the further north it is – and this morning’s earthquake was about 1000km north of us. … Energy from the tsunami goes out perpendicularly to the fault line. The fault line runs north to south, so the energy goes east to west – and we’re to the south.” I wish we had had a good explanation much earlier as to why the people of Tauranga and Auckland were in no danger.

So, re the Kermadecs, humanity may be uniquely lucky. Firstly, the quakes there are usually just not quite big enough to unleash really dangerous waves. Second, the directions that are perpendicular to the huge faultline lead either to ’empty’ parts of the Pacific Ocean (to the east-southeast), or towards New Caledonia (which is aligned to minimise damage from the Kermadecs) and from there towards the Great Barrier Reef (west-northwest) of Raoul Island where the geography probably favours a dissipation of large waves before they reach the north Queensland coast or the island of New Guinea.

New Zealand’s tsunami risk remains mostly from local events on the East Coast of the North Island, south of East Cape. Less likely but potentially lethal events that could hit Auckland or Tauranga would be major undersea volcanic eruptions in the Hauraki Gulf or Pacific Ocean, or an underwater landslide from Hawaii. Indeed, there is evidence of an ancient 100 metre tsunami on the cliffs near Wollongong, Australia. That tsunami probably hit Auckland and Tauranga too.

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Keith Rankin, trained as an economic historian, is a retired lecturer in Economics and Statistics. He lives in Auckland.

contact: keith at rankin.nz

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