Preparing to image Macquarie Ridge
Rajesh Erigela testing the Ocean Bottom Seismometer (OBS) systems. Image: Rajesh Erigela
Recently, researchers from the Australian National University prepared a suite of NCRIS-enabled ocean bottom seismometers (OBS) to image the 3D structure of the Macquarie Ridge Complex — an underwater geological landscape that evolves as three tectonic plates converge and rumble just south of the Australian mainland.
This project will allow an international team of scientists to study the unique location from geological and hazard perspectives in the coming years.
Like all good geology adventures, this story starts out with a team of enthusiastic geoscientists, a good plan, and AuScope toolkit at hand.
The team of five OBS technicians, including Sam Rayapaty, Rajesh Erigela, Robert Pickle, Andrew Latimore and Raymond de Graaf, started by travelling from Canberra in Australia's east to Exmouth on Australia’s west coast with a fleet of AuScope Ocean Bottom Seismometers (OBS). The fleet will soon be shipped to Hobart, where it will be stored until the RV Investigator pulls into dock, and then they, and the extended international research team will voyage to Macquarie Ridge Complex in 2020.
The crew, from left to right: Rajesh Erigela, Sam Rayapaty, Raymond de Graaf, Robert Pickle and Andrew Latimore from Australian National University. Image: Rajesh Erigela
This will be the first purely research deployment of the OBS fleet and is aimed at imaging the 3D lithospheric structure and understanding great earthquakes of the Macquarie Ridge Complex.
The Macquarie Ridge Complex is the result of oblique compression between the Indo-Australian and Pacific tectonic plates and is a rare example of uplifted oceanic crust. It is also the site of the largest strike slip earthquake of the 20th century — Mw 8.2 in 1989 — making this project important in the context of tectonics and hazard.
The Macquarie Ridge Complex marks the convergence of Indo-Australian, Pacific, and Antarctic plates, giving rise to underwater earthquakes (white dots in left image by Pimvantend, NOAA, ETOPO) and marine life that are apparently happy with their slightly shaky setting (right, image by NIWA via the ABC).
In order to ready the OBS fleet for deployment in this challenging southern location instruments have had larger lift rings fitted to help with recovery, and a shipping container has been fitted out to house the seismometers onboard the RV Investigator. Instruments are also having various system checks carried out and deployment crew are receiving training.
The OBS fleet (left) and new lift rings being fitted to the OBS fleet (right). Images: Rajesh Erigela
Lead investigator, Prof Hrvoje Tkalčić from the Australian National University is proud of this project’s ‘mission impossible’ collaboration:
“It has been a challenge to achieve partnership and cohesion among various bodies and funding agencies including the streamlining of timings. We are grateful to the Marine National Facility, the Australian Research Council and the Natural Environment Research Council, UK for their extremely generous support to make the AuScope vision possible.
At the same time, we are still working with the Australian Antarctic Division (AAD) and Tasmania Parks and Wild Services, and hoping to reach a compromise that would allow us access to Macquarie Island and help answer the AAD’s mission to answer the big scientific questions”.
Indeed, the aims of the project are to answer some of the greatest unanswered questions in Earth sciences. Hrvoje explains:
It will be the first study to elucidate the processes generating the world's largest submarine earthquakes not associated with active subduction, which may lead to understanding of how subduction initiates, the mechanism of earthquakes occurring at convergent margins, and more accurate estimates of earthquake and tsunami potential.
Wild weather conditions in the Southern Ocean that the team can expect to encounter on the upcoming voyage to Macquarie Ridge, where three tectonic plates collide and give rise to a unique seafloor environment. Video: CSIRO
Hrvoje looks forward to working with Dr Caroline Eakin from The Australian National University, Prof Mike Coffin from the University of Tasmania, Prof Joann Stock from the California Institute of Technology, and Prof Nick Rawlinson from the University of Cambridge to advance scientific understanding of the globally unique location:
“This study will put Australia at the forefront of Earth Science research into the evolution of tectonic plates and has the potential to better inform hazard assessment efforts in the region, benefiting policy-makers and at–risk communities along the Australia coastline.”
AUTHORS
By Jo Condon (AuScope) and
Dr Michelle Salmon (ANU)
LEARN MORE
Please contact lead investigator,
Prof Hrvoje Tkalčić, (ANU) or
follow his updates online at
The Earth’s Inner Core