Scientists study potential for large, seafloor landslides from Fraser Island to Yamba

5 February 2013

A researcher retrieving the dredge on the Southern Surveyor.
A researcher retrieving the dredge on the Southern Surveyor.

A team of scientists from the University of Sydney have mapped deep-sea canyons and found evidence of large ancient submarine landslides between Fraser Island and Yamba that had the potential to generate a tsunami.

It's the second research voyage into this area for geologist, Associate Professor Tom Hubble, from the School of Geosciences at the University of Sydney.

"The circumstance needed to trigger one of these landslides, is a moderately large and shallow earthquake measuring more than 6.5 or 7 on the Richter Magnitude Scale, which might happen once every 5000 to 10,000 years in south-eastern Australia," Dr Hubble said.

"Importantly the data we collected on the voyage indicate that in fact most of the landslides probably occurred at least several million years ago and that they may be older still."

Dr Hubble led a team of scientists on the three week research voyage onboard Australia's Marine National Facility research vessel, the 66 metre Southern Surveyor to study the seafloor along the continental shelf off the coast of South-East Queensland.

"We used Southern Surveyor's multi-beam echo-sounder to map the seafloor down to three kilometres below the sea-surface and took mud and rock samples from the continental slope - that's the outside edge of Australia that separates the shallow continental shelf from the deep sea floor," Dr Hubble said.

The research is part of a long-term study, looking at submarine erosion and landsliding on the eastern seaboard. The team is investigating how often these slides have occurred in the past as well as trying to figure out what the potential triggers are.

"This voyage has allowed us to get more data and increase the area of seafloor mapped in detail, as well as collect sediment cores and rock samples from new, uninvestigated sites. This will help us better understand how often these submarine slides occur and why they happen in the first place."

The seafloor around Fraser Island is unique, as there is a significant canyon not too far from the coastline, which creates an upwelling and attracts a wide range of marine species to feed on the nutrient-rich waters. It is here substantial data was collected on the voyage.

"Preliminary data was collected in 2008 onboard Southern Surveyor, showing that intense submarine erosion and submarine landsliding has occurred on the continental slope offshore northern New South Wales and South-east Queensland," Dr Hubble said.

Prior to the voyage Dr Hubble was approached by Australia's Marine National Facility (AMNF), to see if he would allocate an hour of his research time to mapping a section of seafloor off the coast of Byron Bay, to map suspected location of the WWII wreck of MV Limerick.

The Office of Environment and Heritage within the NSW State Government had strong suspicions about the location of the MV Limerick and late last year they had, with the support of the NSW Water Police, attempted to map the area by sonar but it was unsuccessful because of rough weather.

Dr Hubble's research voyage was already scheduled to operate in the suspected wreck area.

"When the team at AMNF contacted me to see if we could locate the wreck from onboard Southern Surveyor, we were pleased to assist," Dr Hubble said.

"Finding the wreck of MV Limerick is in the national interest. We were already in the area, we had the necessary technology and technical expertise onboard, and it didn't take long to create a 3-D image of the wreck," Dr Hubble said.

MV Limerick was a 140 metre merchant ship built in 1925 in the UK and at the time of its sinking, belonged to the Union Steam Ship Company in New Zealand. On its way from Sydney to Brisbane, the vessel was torpedoed at 1am on the 26th April 1943, by the Japanese submarine I-177.

There was 72 crew onboard MV Limerick when it sank; two went down with the ship, a New Zealand engineer and an Australian officer. The remaining 70 spent 10 hours in lifeboats or on rafts, until they were rescued by the minesweeper HMAS Colac.

"It was amazing to see the seafloor images come to life as the sea floor mapping technology transformed the data into a 3D graphic of the ship wreck," Dr Hubble said.
Australia's Marine National Facility research vessel, Southern Surveyor, is an ocean going research vessel, which is owned and operated by CSIRO. The facility is funded by the federal government and is available to all Australian scientists.

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