We Asked An Expert If We Should Be Expecting Another Huge Earthquake In New Zealand

Just after midnight this morning, a 7.5 magnitude earthquake struck near Hanmer Springs, south Canterbury. On top of causing major damage throughout the centre of the country, it also left two people dead.

To find out what is up with our faultlines, we reached out to Kevin McCue who is an adjunct professor at Central Queensland University, President of the Australian Earthquake Engineering Society and Director of the Australian Seismological Centre. He calls bullshit on the theory floating around the internet today that the supermoon is somehow to blame for the earthquake and—though we hate to deliver more bad news—he explains why there's a good chance of yet another major earthquake heading our way.

VICE: Hey Kevin, what can you tell us about the 7.5 magnitude earthquake that struck New Zealand earlier today?
Kevin McCue: This earthquake did not occur where seismologists expect them to, that is on the plate boundary or any of the associated faults of which there are many in the north of the North Island. Our assumption is that if there are obvious large active faults, then that's where the earthquakes should happen. This assumption is built into our models of earthquake hazard for building codes.

Like the Christchurch earthquake sequence of 2010-11, the earthquakes are pointing to faults we didn't know existed which doesn't give engineers a lot of confidence in the current hazard models. Mind you, the situation is a lot more complex in Australia where there is no plate boundary but we do experience large earthquakes.

There's been talk of the earthquake being linked to the supermoon. Can you officially debunk that theory for us?
As the Earth rotates, the earth-moon gravitational field causes tides in the solid Earth with a period of about 12 hours. The so-called supermoon is a bit closer than usual, but not enough to radically change the induced stresses in the Earth's crust. If the moon were a trigger for earthquakes, then earthquakes should occur on average every 12 hours or some multiple of that, and they don't.

That makes sense. How predictable is an earthquake like the one we saw this morning? Is there anyway we could've seen it coming?
No. Earthquakes are not predictable, not anywhere. What seismologists attempt to do is say where earthquakes are most likely to happen i.e. in New Zealand along the plate boundary, and then measure their frequency and work out the probability of an earthquake of some specified magnitude occurring in the next 50 or 100 years at some point.

For example, we can say that a magnitude 8 earthquake might be expected somewhere in New Zealand every 100 years on average. It is most likely to occur on the 1000km long plate boundary system of faults and will rupture a 300km length of one or more of the faults.

A city like Wellington should expect to be struck every 300 years on average. The last occasion was in January 1855.

What does the quake mean for the rest of New Zealand?
The Canterbury earthquakes (including the current ones) have thrown a lot of uncertainty about the hazard assessment process, but New Zealand is not called the Shaky Isles for nothing. Earthquakes can occur anywhere in New Zealand; they are more likely to occur in some places than others, and on the plate boundary rather than off it.

All new buildings should be designed to resist earthquakes according to the current code, which should ensure that they will not collapse (though they may have to be demolished after the next earthquake which is what happened in Christchurch). Building owners shouldn't grumble about having to design and construct their buildings to be safer, but they do. Special structures like Te Papa have been base-isolated, [which means they were] founded on an elegant New Zealand designed system of springs and dampers to isolate the building from the ground to substantially decrease the shaking during an earthquake.

People here are on edge, to say the least. How worried should we be that a bigger earthquake could be on the way?
In 1929 there were two major earthquakes just months apart in the North Island and then two years later the destructive Hawke's Bay earthquake occurred. Earthquakes do cluster in time so there is a good chance of yet another major earthquake occurring, but where and when is totally unknown.

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