Deep sea robot in quake study

Jason unearthing secrets of the deep.

Jason unearthing secrets of the deep.

JUST CHECKING: Samples being collected following the deployment of a Mosquito fluid flowmeter that will be left at this site for the next two years to measure changes in rates of fluid flow. Pictures by Woods Hole Oceanographic Institution.
ALL SORTS: The abundance of life visible on this rocky outcrop is an example of the diversity seen during NDSF ROV Jason dives along the Hikurangi subduction zone.

An international team of scientists researching earthquakes off the coast of Gisborne have been getting a helping hand from a deep-sea-diving robot.

After completing the second of three planned research voyages, scientists on board the US research vessel Roger Revelle employed an underwater remotely operated vehicle (ROV) called Jason to instal sea floor instruments, collect samples, and download data from earthquake observatories along the Hikurangi subduction zone.

Voyage leader Evan Solomon from the University of Washington in Seattle, US, said the information would help them to understand the role water deep beneath the sea floor played in affecting the likelihood and type of earthquakes that occur along the subduction zone.

“Water emerging at the sea floor is a messenger from the deep.

“The make-up of the water will tell us about the environment deep down beneath the sea floor where earthquakes occur.

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

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

“This is the first time an ROV has been used at the Hikurangi subduction zone, giving us an amazing opportunity to survey sites where water is venting at the sea floor and collect valuable observations of these environments and fauna around the vent sites,” GNS Science marine biologist and geophysicist Jess Hillman said.

“This will help us to understand the wider processes that drive the likelihood and type of earthquakes that occur at faults beneath the sea floor.”

ROV Jason also discovered “dense” fields of tube worms and mussels.

Dr Hillman said the “sheer volume” of sea life was a surprise.

“We expected to find them there. The reason we are targeting those areas is because we know those fluids being released from the sea floor will attract those animals who will use that as a food source, but it was just the sheer volume of them that wasn’t quite what we expected.

“There was a huge diversity of animals down there, which was really good to see.”

Using the robotic vehicle meant the site could be studied in much more detail.

“The overall aim of the project is that we are using the observations and the samples we have taken to learn more about what is happening beneath the sea floor.

“If we can understand that better it helps us to understand why things like the slow-slip earthquakes are happening and that feeds back into the geo-hazard research which GNS has a big part in.”

The robotic vehicle Jason also retrieved data from two earthquake observatories that were installed on the sea floor by the research vessel JOIDES Resolution early last year to monitor slow-slip earthquakes off the coast of Gisborne.

The observatories were installed 30 kilometres off the coast of Gisborne to monitor the activity of the Hikurangi subduction zone.

The observatories, one named by Gisborne students, are at the northern end of the subduction zone, where the Pacific plate dives beneath the North Island.

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.

“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 to figure out why they occur,” GNS Science geophysicist Laura Wallace said.

The data and samples recovered by ROV Jason would provide information on changes in the rock and sediment surrounding the subduction fault, giving clues about how and where stress is building or being relieved.

Dr Wallace said she hoped to have some initial findings from the recovered data very soon but pointed out that there had not been a slow-slip event since the observatories were installed.

It was hoped another voyage next year would show recordings of a slow-slip event.

An international team of scientists researching earthquakes off the coast of Gisborne have been getting a helping hand from a deep-sea-diving robot.

After completing the second of three planned research voyages, scientists on board the US research vessel Roger Revelle employed an underwater remotely operated vehicle (ROV) called Jason to instal sea floor instruments, collect samples, and download data from earthquake observatories along the Hikurangi subduction zone.

Voyage leader Evan Solomon from the University of Washington in Seattle, US, said the information would help them to understand the role water deep beneath the sea floor played in affecting the likelihood and type of earthquakes that occur along the subduction zone.

“Water emerging at the sea floor is a messenger from the deep.

“The make-up of the water will tell us about the environment deep down beneath the sea floor where earthquakes occur.

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

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

“This is the first time an ROV has been used at the Hikurangi subduction zone, giving us an amazing opportunity to survey sites where water is venting at the sea floor and collect valuable observations of these environments and fauna around the vent sites,” GNS Science marine biologist and geophysicist Jess Hillman said.

“This will help us to understand the wider processes that drive the likelihood and type of earthquakes that occur at faults beneath the sea floor.”

ROV Jason also discovered “dense” fields of tube worms and mussels.

Dr Hillman said the “sheer volume” of sea life was a surprise.

“We expected to find them there. The reason we are targeting those areas is because we know those fluids being released from the sea floor will attract those animals who will use that as a food source, but it was just the sheer volume of them that wasn’t quite what we expected.

“There was a huge diversity of animals down there, which was really good to see.”

Using the robotic vehicle meant the site could be studied in much more detail.

“The overall aim of the project is that we are using the observations and the samples we have taken to learn more about what is happening beneath the sea floor.

“If we can understand that better it helps us to understand why things like the slow-slip earthquakes are happening and that feeds back into the geo-hazard research which GNS has a big part in.”

The robotic vehicle Jason also retrieved data from two earthquake observatories that were installed on the sea floor by the research vessel JOIDES Resolution early last year to monitor slow-slip earthquakes off the coast of Gisborne.

The observatories were installed 30 kilometres off the coast of Gisborne to monitor the activity of the Hikurangi subduction zone.

The observatories, one named by Gisborne students, are at the northern end of the subduction zone, where the Pacific plate dives beneath the North Island.

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.

“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 to figure out why they occur,” GNS Science geophysicist Laura Wallace said.

The data and samples recovered by ROV Jason would provide information on changes in the rock and sediment surrounding the subduction fault, giving clues about how and where stress is building or being relieved.

Dr Wallace said she hoped to have some initial findings from the recovered data very soon but pointed out that there had not been a slow-slip event since the observatories were installed.

It was hoped another voyage next year would show recordings of a slow-slip event.

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