A massive fault separating tectonic plates under New Zealand triggered the Kaikōura Earthquake, according to a new scientific paper.

The authors suggest their findings will help predict where future shaking might happen by understanding and modelling the plate boundary, known as the megathrust.

The large fault between the plates moves freely at depths of 30 kilometres or more, but at shallower depths is locked in place under central New Zealand.

DEREK FLYNN/FAIRFAX NZ The Kaikōura Earthquake shattered the landscape at the northeast of the South Island.

The combination of steady movement in some places and no movement in others slowly forced the southern North Island and northern South Island to bend.

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That movement put extreme stress on the landscape, causing the 7.8 magnitude Kaikōura quake in 2016, Victoria University geophysicist Associate Professor Simon Lamb, who led the research, said.

SIMON LAMB New Zealand is on the boundary between the Australian and Pacific tectonic plates. The locked portion of the underlying megathrust is shown in pink.

"The Kaikōura Earthquake initiated a complex pattern of fault movement, essentially shattering the landscape, and causing a cascade on 20 or more faults."

The researchers came to their conclusion about the role of the megathrust using nearly 20 years of GPS data to understand the slow movements of the landscape leading up to the Kaikōura quake. That provided a "very very accurate" picture of the build up of stress and forces, Lamb said.

The movement shown in the high resolution GPS data could be explained "incredibly well by this very simple process of the megathrust slipping at depth".

SUPPLIED The 2016 Kaikoura earthquake destroyed road and rail along the South Island's east coast.

"We have a very, very good image of how the landscape of New Zealand is moving day in and day out and that movement is, if you like, the build-up to the next big earthquake," Lamb said.

"We found if you look at the zone of rupturing in the Kaikōura Earthquake, it's not really related to any particular fault at the surface, but it follows the way that the megathrust has been slipping. The zone that actually broke follows how the megathrust had been moving in the 20 years prior to the earthquake. There seemed to be a simplicity in all of this."

The findings from the research were different to the widely held view that each big fault had its own driver and pacemaker, which determined when earthquakes happened on individual faults.

SIMON LAMB A 3D perspective view of the deep slipping surfaces under central New Zealand.

"The approach has been very, what I would call fault-centric. Because earthquakes are sudden movements on a fault, it's always been assumed that the fault somehow has an identity that extends beyond the earthquake," Lamb said.

"What people have thought is that with big faults anywhere in the world, the deeper part of any big fault is moving all the time. And the shallower part isn't moving, it's stuck or locked, and it catches up with the deeper part in an earthquake.

"What we are saying is specifically for New Zealand, but it may well apply to other places as well, we don't think that is the case. We think with the big faults, they aren't slipping deeper down all the time, between the big earthquakes they don't exist at all, there's nothing moving at all.

NIWA Niwa marine geologist Dr Joshu Mountjoy talks about investigating the impact of the Kaikoura Earthquake on the Kaikoura Canyon. Researchers found the quake caused a "huge slipping event", with mud being removed from almost every part of the canyon's upper slope.

"What is moving is the ginormous fault, the megathrust. When it has slipped sufficiently, when that overlying material has reached its limit, then the whole system shatters, and it shatters by breaking all over the place."

Lamb expected the paper, published on Tuesday in Nature Geoscience, to be widely discussed. "It's quite a new idea. We encountered, as you do in science, lots of counter arguments from reviewers, but we finally convinced people of our ideas.

"It basically outlines a new approach to thinking about how you might go about forecasting earthquakes. This approach moves away from focusing on individual faults and moves toward when is the likelihood of the whole system breaking."

IAIN MCGREGOR/STUFF Seabed raised by the earthquake by SH1, north of Kaikoura.

Hopefully people working in the area of quake forecasting would see the approach set out in the paper as something to try.

"I think with something as important as earthquake forecasting, you really want to try everything," Lamb said.

More immediately, he thought the paper showed how GPS data should be interpreted.

"I think that will have a much more immediate impact, while the implications for earthquake forecasting will be slightly further down the road, and potentially more controversial."