Cosmos

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.

 ?? ??

Newspapers in English

Newspapers from Australia