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Expedition to uncover geological secrets of Macquarie Island

 

A voyage on the CSIRO’s research vessel RV Investigator is being conducted by MAS and ANU scientists to map the seafloor surrounding Macquarie Island.

The expedition is a joint effort between the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS) and Australian National University (ANU).

The 24-day voyage, which is being led by IMAS professor Mike Coffin, will observe the underlying structure and geological evolution of Macquarie Island, which is a United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage Site.

ANU professor Hrvoje Tkalčić will add seismometers to the seafloor around the island to investigate the crustal and mantle structure of the area, along with its seismicity. The seismometers will be recovered in late 2021 to early 2022.

The voyage will capture the first high resolution maps of the island’s seafloor, which will also assist in monitoring future earthquakes and tsunamis that may impact Australia and New Zealand.

“The creation of seafloor maps identifying faults, fracture zones, and relict seafloor spreading centres will yield insights into the structure, behaviour, and history of this important plate boundary, which presents significant tsunami hazards for both sides of the Tasman Sea,” Coffin told the University of Tasmania.

“The maps will also shed light on why and how Macquarie Island, which formed around 2500 metres below sea level, was thrust above sea level.”

Macquarie Island has no permanent residents and is situated about 1500km south-southeast of Tasmania. It sits on the tectonic plate boundary between the Australian and Pacific plates, which is highly active and produces large intra-oceanic earthquakes.

“Our research has two main aims: first, to image Earth structure by utilising state of the -art seismological techniques in conjunction with a carefully designed configuration of ocean bottom seismometers pointing towards the Earth’s centre like a giant antenna; and second, to elucidate the physics of the world’s largest underwater earthquakes not associated with active subduction,” Tkalčić said.

“Such a remote and unique location chosen for our experiment will also improve the spatial coverage of the Earth’s deepest interior by seismic waves of distant earthquakes recorded by our seismometer array, and enable a range of geophysical studies, including interactions of the ocean and atmosphere with the solid Earth.”