Rare landslides and earthquakes could hit coastlines with potentially disastrous consequences, according to a new publication being promoted by the Australian Government.
A new book from CSIRO Publishing warns “continental scars” off the East Coast of Australia could trigger tsunamis in the event of a landslide or major earthquake.
The research, undertaken by the University of Sydney’s School of Geosciences, is outlined in a chapter of Southern Surveyor: Stories From on Board Australia’s Ocean Research Vessel.
“It’s hard to understand how these slopes ever fail, yet the evidence is they can, because there are enormous scars, or scoops, along the continental margin from Bateman’s Bay to Fraser Island,” university associate professor Tom Hubble, the lead researcher on the project, says in a public statement.
“One of the largest examples of these continental scars is located off Bulli in New South Wales, and is 9 km (5.6 miles) wide, 16 km long (9.9 miles) and roughly 300 to 400 meters (328 to 437 yards) thick.”
These landslide events and the earthquakes are extremely rare, according to Hubble and his team.
“You might get one landslide every 10,000 years that could generate a wave of more than five meters in height. A wave height of more than 20 meters would only occur every 100,000 or even every million years,” he says.
“The big questions for us are how many, how big, and how often? And we’re making some progress on this.
“We have actually identified 400 landslides that have occurred over the last four million years that are big enough to have generated a tsunami, most of which would have generated a tsunami with a one to two yard wave height.
“Around 50 to 100 of these could have generated something around five to ten yards in wave height, which is the size of the tsunamis that came through Indonesia and Japan.
“We need to do more investigation to constrain these numbers reliably.”
Researchers believe the landslides could be triggered by large earthquakes, likely of magnitude-6 to 7, and are now investigating this theory.
“We are interested in conducting further studies in a section referred to as ‘the Block’ near Brisbane, which is about 546 yards thick and 10 km long (6.2 miles), and has noticeable tension cracks.
“If an earthquake of the right magnitude occurred, we believe it could trigger a significant tsunami.”
Understanding these scoops and their potential sites, as well as their tsunami generating capabilities, has so far been restricted by the sonar technology on board the vessel Southern Surveyor, which could only map the sea floor to 3 km (1.86 miles).
The continental slope begins about 50 km (31 miles) off the Australian coast and drops away to the abyssal plain, which is four to five km (2.5 to 3.1 miles) deep.
Southern Surveyor: Stories From on board Australia’s Ocean Research Vessel follows the adventures of the men and women on board the CSIRO Marine National Facility research vessel over the course of a year, as told by author Michael Veitch.
For 10 years, the Southern Surveyor represented the vanguard of Australian blue water marine science. On more than 100 voyages, this former North Sea fishing trawler with her distinctive blue and white livery carried scientists and technicians across the Southern, Pacific, and Indian Oceans, as well as the waters off northern Australia.
Hear stories of the Southern Surveyor research vessel: