Disaster planners set to benefit from research ship's seismic survey off New Zealand's East Coast

"Unprecedented" 3D imagery of Hikurangi subduction zone hopes to hold the key to secrets of "slow slip" quakes.

The US research vessel, the Marcus Langseth with a group of international scientists on board, has arrived back in the port of Napier after five weeks away mapping fault lines off the North Island's East Coast.

"It's not just a map it's even better than that, it helps us make a 3D image of the subduction system so we can see all the faults in their complexity," lead geophysicist Dr Harold Tobin told 1 NEWS.

Researchers have been setting off over 40 sound sources in the water attached to 24 kilometres of cables with pressure sensors attached called seismic streamers.

They record the echoes that bounce back off the ocean bed.

The data is recorded every 30 seconds every day for 30 days, creating a detailed map of layers beneath the sea floor.

"We can see the strong spots or the week spots on the fault or the places where it's got complex structure and places it's got simple structure and all that helps seismologist and geologist."

It's hoped the mapping will help better understand the phenomenon of "slow slip" earthquakes which occurring frequently in the Hikurangi subduction zone.

Dr Dan Barker from GNS Science who has been on the vessel the past five weeks says the shaking from "slow slip" earthquakes isn't felt.

"They are effectively releasing energy the same way a large earthquake would but the big difference is they are happening slowly, a timeline of weeks to months."

The 7.8 magnitude Kaikoura earthquake in 2017 is believed to have triggered a slow slip off event off the coast of Gisborne.

Dr Harold Tobin says the preliminary results have already turned up interesting findings.

"What we have found that really is new is the complexity of that subsurface geology, there are faults that are winding round in all sorts of different places in 3D configurations."

The research will be used globally as well as locally by our own disaster planners.

Lisa Pearse from Hawke's Bay Civil Defence says research like this is amazing for preparing for those future disasters.

"We are really keen to learn about the risk of living in the subduction zone and what it means for our communities."

However, the findings won't be known for a few years yet as the data now will go away to be analysed.

A US research ship spend five weeks carrying out scientific research. Source: 1 NEWS