New Zealand has been hit by three significant earthquakes in the last two days. Luckily not strong enough to do damage, and remote enough that even a larger shake would have been more nuisance than apocalypse. But they are a sharp reminder that we live on some very ‘shaky isles’. The next one might well bring tragedy.
It’s to get a better handle on that looming apocalypse that GNS Science have been exploring the Alpine Fault this past few months – drilling far down to set up an early warning system that will give us some prior hint when is about to rupture. Not if, but when – this fault moves every three centuries or so, and it last ruptured in 1717. Go figure.
Well, actually you don’t have to. A study published in 2012 indicated there was a 30 percent chance of a devastating quake occurring on that fault some time in the next 50 years – before 2062. Because probabilities are calculated as bell-shaped curves, this did not mean a quake would occur precisely in 2062; it meant the quake might occur any time from 2012 (low probability) through the mid-twenty-first century (high probability), to the early 2100s (a low chance of it happening that late, but a very high probability of it happening, if it hadn’t happened by then).
This fault is thought capable of generating quakes with magnitude of up to 8.3. Huge. A Civil Defence exercise held in 2013, built around that potential, can best be described as scary. While researching my book on earthquakes, I contacted the author of the exercise – who filled me in on the details. Uh…ouch.
For obvious reasons the science of earthquake engineering is well developed in New Zealand. Some of the world’s leading systems have been invented here, notably the lead-rubber base isolator. This is designed to keep a building ‘floating’ above its foundations. When an earthquake hits, the ground moves – but, thanks largely to its moment of inertia and the reduced energy being transmitted to it, the building doesn’t. Not so much anyway. The first system was installed in the early 1980s in what was then the Ministry of Works building, and major structures to receive it since have included Te Papa Tongarewa, the national museum; and Parliament buildings.
It’s a clever idea. And tricks like this – along with a raft of others – all have to be applied quite seriously in earthquake zones. One of the outcomes, certainly as far as civil defence planning is concerned, is that the likelihood of casualties during the quake is reduced. Buildings constructed with proper attention to earthquake-proofing won’t collapse, and if they’re done right, they also won’t shed parts that crush people beneath. That’s what caused most of the casualties in the 1931 Napier earthquake, for instance, which provoked New Zealand’s first serious earthquake-proofing regulations.
Study, inevitably, is ongoing. But what I can say is that New Zealand doesn’t need to worry about a ‘zombie’ apocalypse. The ‘earthquake’ apocalypse we’re actually facing is serious enough. For more…well, you knew I’d say this – it’s all in my book.
Copyright © Matthew Wright 2014