Return of the seismometers dropped on the ocean floor: an update

Just over a year ago, a team of researchers voyaged out to the Southern Ocean to drop nearly 30 seismometers onto the sea floor, in order to learn more about earthquakes and tsunamis. They deployed 27 instruments on the Macquarie Ridge, some at depths below 5,000 metres, and placed five on Macquarie Island.

A few weeks ago, another crew on the RV Tangaroa set out to retrieve the seismometers. Cosmos chatted to Professor Hrvoje Tkalčić, of the Research School of Earth Sciences at the Australian National University, about what they were doing and how they’d get the instruments back.

You can read more about the mission here.

The Tangaroa has now returned, and the researchers have been able to take a preliminary look at the findings.

Retrieving obs 850
Scientists Ian Smith, Ollie Twigge and Sam Harrison retrieving one of seismometers from the ocean floor. Credit: Joshu Mountjoy / NIWA.

“We successfully recovered 15 out of 27 ocean bottom seismometers,” says Tkalčić.

“As soon as we get the data, we will employ a comprehensive arsenal of seismic imaging techniques to understand the nature of the central Macquarie Ridge Complex and the associated earthquakes.

“We expect that the digital data will become available to our team by mid-January, 2022.”

The researchers have also independently made some interesting conclusions about the Macquarie Ridge, based on data they collected during their first voyage. They found mass wasting – movement of rocks – down either slope of the Macquarie Ridge. This wasting could have been caused by earthquakes – there were two large ones in the area in 1989 and 2004.

“The discovery of enormous mass wasting presents a paradigm shift in terms of where the tsunamigenic potential for the Macquarie Ridge may lie,” says Tkalčić.

“Namely, tsunamis can be caused by earthquakes, as we all know, and this was one of the premises of our research proposal, but large underwater landslides also cause them.

“In fact, there is ongoing research in conjunction with other world locations where underwater landslides caused tsunamis. And with our voyages to the Macquarie Ridge, the world has just gotten another place of massive landslides hidden by the vast ocean to study, understand and consider for the future.”

And what about the 12 seismometers left behind?

“My colleagues and I are very keen on trying to recover them from the ocean floor either through seeking collaboration with other scientists, support from tech billionaire sponsors, or other unexpected opportunities,” says Tkalčić.

So if you’re listening in, Branson or Bezos – if you can get to space, you should be able to help these researchers retrieve their instruments!

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