Why would you drop 27 seismometers on the ocean floor?
And now they’re there… how do you get them back?
Near Macquarie Island in the Southern Ocean, a research vessel recently attempted to retrieve 27 seismometers from the sea floor to find out what drives earthquakes and tsunamis.
The research is part of a long-term project to learn about the undersea earthquakes and landslides that occur around the Macquarie Ridge – a subduction zone halfway between New Zealand and Antarctica – and how these tremors might affect coastal populations in Australia and New Zealand.
“In order to do that, we first need to understand the underground,” says Hrvoje Tkalčić, from the Australian National University.
“The continuing waveforms that these instruments record will help us do that.”
In October 2020, Tkalčić and colleagues journeyed to the remote island on the CSIRO research vessel Investigator. They dropped 27 seismometers on the ocean floor, some to depths below 5,000 metres, and deployed a further five on the island.
After 12 months of continuous data recording, the New Zealand research vessel Tangaroa returned to collect the seismometers.
They were connected to concrete ballasts when dropped, but these were fitted with a release mechanism. When instructed, the seismometers disconnected from the concrete and floated to the surface.
“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.”
As for the 12 seismometers left behind, Tkalčić hopes for a tech billionaire to fund retrieval.