Hikurangi subduction zone: NZ's most mysterious earthquake faultline reveals a 'messenger from the deep'

An international team of scientists studying one of NZ's most mysterious, and potentially dangerous, faultlines have discovered water emerging from vents in the seafloor.

Secrets of the Hikurangi subduction zone, off Hawke's Bay on the east coast of the North Island, are beginning to be revealed by an underwater remote operated vehicle called Jason.

Water is bubbling from vents in the seafloor along the Hikurangi subduction zone. Photo / Woods Hole Oceanographic Institution

Photos from Jason's dives, released today, show a vast diversity of corals and deep sea wildlife, the likes of which have never been seen before in the area along the east coast of the North Island.

They also show water emerging at the seafloor, a natural phenomenon of the Hikurangi zone that voyage leader Evan Solomon says is a "messenger from the deep".

Scientists are now back in Auckland after the journey a trip aboard the US research vessel Roger Revelle.

They used Jason to install seafloor instruments, collect samples and download data from earthquake observatories along the Hikurangi subduction zone.

A vast diversity of corals and deep sea wildlife, the likes of which have never been seen before along the east coast of the North Island, was found. Photo / Woods Hole Oceanographic Institution

The information will help them understand the role that water deep beneath the seafloor plays in affecting the likelihood and type of earthquakes that occur along the zone.

"The make-up of the water will tell us about the environment deep down beneath the seafloor where earthquakes occur."

The seafloor instruments installed during the expedition add to an already large and diverse number of instruments currently monitoring the Hikurangi subduction zone offshore.

Scientists say studying the wildlife near the vents will help them with future earthquake predictions. Photo / Woods Hole Oceanographic Institution

It's the first time an ROV has been used at the Hikurangi subduction zone

It allows scientists to survey sites where water is venting at the seafloor and collect valuable observations of these environments and fauna around the vent sites.

"This will help us to understand the wider processes that drive the likelihood and type of earthquakes that occur at faults beneath the seafloor," Jess Hillman of GNS Science says.

Jason also retrieved data from two earthquake observatories that were installed beneath the seafloor early last year to monitor slow slip earthquakes off the coast of Gisborne.

Slow slip earthquakes are where movement between the tectonic plates occurs slowly across the subduction zone, over a period of weeks to months, rather than suddenly in a large earthquake.

Jason in action under water. Photo / Woods Hole Oceanographic Institution

These slow slip earthquakes occur every one to two years off the coast of Gisborne and it is considered one of the best places in the world to study these types of earthquakes.

"We are hoping that we will sense and record changes in the Earth during at least a few cycles of these slow slip earthquakes over the next several years so we can try and figure out why they occur," Laura Wallace from GNS Science says.

According to Solomon, this is the first step of many to finding the connection between earthquakes and slow slips.

"This is only one piece of the puzzle we are slowly putting together to better understand the relationship between earthquakes and slow-slip earthquakes."