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.
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.
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