Predicting a quake's impact: Kiwi scientists model seismic waves to identify at-risk buildings
Imagine if just like forecasting the weather, scientists could one day predict how hard an earthquake would rock any given area and which buildings might take the biggest hit?
It's becoming a reality - and Kiwi experts are leading the way internationally.
The science isn't about predicting when or where an earthquake will hit - that's impossible - but about knowing how the ground will shake and where when a quake hits, and even being able to tell emergency responders where best to direct their efforts.
For all the damage they've caused, the Canterbury and Kaikoura earthquakes have provided scientists with crucial data to map ground shaking, and to get a better understanding of when the seismic wave from a quake will reach a given area.
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That means quake experts like Canterbury University earthquake engineering Professor Brendon Bradley can make informed predictions about how the ground will move in a certain spot.
"We, of course, didn't know that there was going to be the Kaikoura earthquake in November last year, but once you tell me there was an earthquake in Kaikoura, the top part of the earthquake was 60km from Wellington, [and ask] 'what type of buildings do you think it's going to have the strongest influence on?', I would loosely have been able to say to you '10 to 20-storey buildings'," he says.
Bradley is the deputy director of QuakeCORE, the New Zealand Centre for Earthquake Resilience, a group of quake experts and their students who, since 2012, have been working on a system to model the "process" of an earthquake.
From that, they've been able to create videos showing the ripple of a quake's energy into surrounding areas, and its impact on buildings.
Earlier this year, the group released an animation of the Kaikoura earthquake, showing its energy rippling up the South Island to Wellington, and the way the capital's buildings were rocked as those ripples arrived.
"What we wanted to illustrate there was the reason why, in Wellington, we tended to see more damage to buildings of 10 to 15 storeys tall, whereas we didn't really see any damage to short buildings and we didn't really see any damage to really tall buildings, and that was the particular properties of the ground shaking in the Wellington region," Bradley says.
It makes for a cool video - but that's not the sole reason for the modelling: the animations not only help the public understand why the earth below their feet is moving the way it is, but also help scientists get a stronger grasp on how to make predictions in future.
Over the past five years, with the help of two government-funded supercomputers in Auckland and Wellington, QuakeCORE has developed the ability to create real-time estimates of quake impacts.
When a tremor hits, the centre instantaneously receives data from Geonet, and an automated process of calculations "tells us exactly what level of ground shaking we expect in different areas of New Zealand as a result of that earthquake".
It can take 30 to 60 minutes to produce results - "enough time to let emergency agencies know what sort of damage to expect and how they can prepare for reconnaissance or emergency response", Bradley says.
"Our idea is basically to get to a point where we provide the same sort of information as a weather forecaster would tell you … Just as when you have a severe weather warning, we would provide you the same information about severe ground shaking and the consequence to buildings."
In a way, Bradley says, New Zealand's been "fortunate" to have its quakes, because it means scientists have become world leaders in modelling the potential impacts.
He's currently on sabbatical at Stanford University in California, USA, where scientists - lacking in local quake data - were able to use New Zealand's quakes to help create their own models.