The Kaikōura earthquake had a devastating impact not just on land, but under the sea as well.
Now scientists are now using a robotic submarine on loan from Sweden to help scan the deep trench off the coast, in a survey that could help predict the fallout from future disasters.
The little robotic sub has had a test launch in Wellington harbour, off NIWA's research vessel, ahead of its trip south.
"It's designed to fly down into the ocean and survey quite close to the seabed, like 50 metres above the seafloor, whereas we'd be surveying from a ship and maybe 1000 metres above water," NIWA marine geologist Joshu Mountjoy told 1 NEWS.
The Kaikōura Canyon is about 60 kilometres long and 2000 metres deep. It was transformed by the 2016 earthquake.
Below the waves, there was an undersea upheaval; 850 million tonnes of sediment cascaded through the canyon.
"It triggered a whole lot of landslides that basically collected a huge amount of mud without and that flowed out of the canyon and travelled at least 600 kilometres along the seafloor," Mountjoy said.
The battery-powered sub uses sonar to help scientists build a clearer picture of how the seabed reacted.
"We really want to understand how that sediment moved. and then understanding the mechanism of landslides particularly," Mountjoy said.
"Those landslides could have generated tsunami. They didn't in this case, but if they were much bigger they could have."
It's technology never used before in New Zealand and scientists have about a month to use it before it returns to Europe.
The robotic submarine was shipped over from Sweden in a container.
It's on loan from a Swedish university under an arrangement with the EU which makes the multi-million dollar piece of equipment free for New Zealand scientists to use.
It'll also provide insight into how marine life is recovering four years after their habitat was changed forever.