New Zealand’s looming seismic time-bomb

New Zealand’s Civil Defence has a new alert system that pushes a really irritating sound out to every compatible phone, no app required, and it can’t be switched off.

Building at 61 Molesworth Street being taken down by an 85-ton ‘nibbling’ crane after the November 2016 Kaikoura quake rendered the structure unsafe.

They tested it on 4 October at 1.32 am and, the other weekend, tested it again. About a third of all cellphones in New Zealand can receive it. It’s a good idea, although whether it was wise of CD to announce the innovation by sending it to every New Zealander at 1.32 in the morning is, of course, another issue. At least it didn’t involve some anonymous voice going: ‘When you hear the air attack warning, you and your family must take cover at once’, or ‘Mine is the last voice that you will ever hear. Don’t be alarmed.’

What it means is that – for the third of Kiwis whose phones are compatible – there will be some warning of tsunami. Probably not quakes, they can’t be forecast to that level. But tsunami happen after quakes, and the timing can be calculated.

The new system is also timely, because there’s a tsunami-generator that’s seized the headlines of late, the Hikurangi Trench – the subduction zone off the east coast where the Pacific plate dives under the Australian. This has the capability to generate a Mw 9 quake off the east coast of New Zealand’s North Island, devastating coastal areas and then flooding them with a tsunami that might arrive seven or eight minutes later in some areas.

Think Japan 2011. Only bigger.

Hikurangi trench, marked up by me on a Google map of New Zealand.

The trench and its seismic potential have been well known for decades. When I wrote my science book on earthquakes, back in 2014, I discussed it with a seismologist I was in contact with at Canterbury University. I also wrote it into the book, and was far from the first to cover it.

The plus side is that the trench has hit the public mind – and that’s good. There’s  work under way to more fully investigate the system. The alarming part is that although thought dormant, the southern section seems to have experienced movement since the Kaikoura quake of November 2016. Ouch. That makes investigation crucial. Earthquakes can’t be predicted – there are too many variables. But they can be generally forecast as a range of probabilities, and those probabilities can be defined if there’s good information about the fault system.

Even then, of course, seismologists are always learning – it’s what science is about. One of the discoveries from the Kaikoura quake was that it involved more than one fault. That’s why Wellington – despite being so far north of the original fault – was so hard-hit. Buildings stood up, but many have been condemned and, as I write this, demolition continues around the city. The possibility of a ‘chain earthquake’ hadn’t been considered before. Now that it’s been discovered, future work will refine the mechanisms.

All of it adds to the tapestry of knowledge about what lies beneath our feet.

Copyright © Matthew Wright 2017

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13 thoughts on “New Zealand’s looming seismic time-bomb

  1. It’ll be even more useful when ALL Kiwis get the message, Matthew
    BTW, I was surprised to see the Australian Plate name is still being used, since the discovery of the New Zealandia plate and continent.

    1. My understanding is that Zealandia spans both the Australian the Pacific plates and is currently being ripped apart by them – it’s not a separate crustal plate of itself. There is an irony to Zealandia, incidentally – years back we used to have a joke that the only thing wrong with Australia was that it was above sea level (typical trans-Tasman joshing, that – their ripostes usually involved Kiwi blokes, gumboots and very nervous sheep, but I digress…) Anyhow, it turns out the joke’s on us because the bulk of New Zealand is, in fact, well below sea level…

  2. That sounds very similar to the situation on the west coast of North America with the Cascadia subduction zone. I don’t think we have a similar phone-based system here as yet, although I’ve heard some talk about one being introduced. It looks like a 90-second earthquake warning is possible too. Not long, but would allow time to get under cover. It’s interesting that some of the world’s most dramatic and beautiful places are in earthquake prone areas.

    1. I wonder if the beauty of the landscape and the quake-proneness is causal – the kind of landscaping that emerges from fault lines also generates fantastic mountains and so forth. Yes, I think the Japanese had a 90 second warning for the 2011 quake – the rupture was picked up at distance. We don’t have such a system in NZ (yet)… and there was a report today that of all the faults known to be capable of generating a 9+ quake around the Pacific rim, only the Hikurangi Fault hasn’t ruptured in known history. Uh…. yay?

  3. I’ve been worried for a while now that New Zealanders were getting too complacent to tsunami risk, so it is great to see this get more publicity. Over a decade ago I worked on a documentary about archaeological evidence of tsunami in New Zealand. The evidence is very scary!

    1. Deeply scary! The guy I talked to at Canterbury had done his PhD thesis on the likely impact of an Alpine fault movement (with secondary rupture of faults near Dunedin) and described an unfolding national disaster of utterly horrific dimension. When I remarked that this was, indeed, devastating he said that actually we faced a worse threat from the Hikurangi Trench.

      1. Very scary indeed! Where were the Dunedin faults if you can recall? Buildings down here are extremely vulnerable. So many were built in the 1880s – 1900s, mostly either on hillsides or reclaimed land. I’ve always suspected that a big shake down here would result in horrific destruction. Most the locals shrug it off, citing how uncommon quakes are here compared to further north. I’m not so confident!

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