EGU23-9886, updated on 26 Feb 2023
https://doi.org/10.5194/egusphere-egu23-9886
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Microseismicity of the Macquarie Ridge Complex

Nicholas Rawlinson1, Tom Winder1, Hrvoje Tkalcic2, Joann Stock3, and Mike Coffin4
Nicholas Rawlinson et al.
  • 1Department of Earth Sciences, University of Cambridge, Cambridge, UK (nr441@cam.ac.uk)
  • 2Research School of Earth Sciences, Australian National University, Canberra, Australia
  • 3Seismological Laboratory, California institute of Technology, Pasadena, USA
  • 4Institute for Marine and Antarctic studies, University of Tasmania, Hobart, Australia

The Macquarie Ridge Complex (situated on the Australian – Pacific plate boundary, in the southwest Pacific Ocean) constitutes a unique geological site, being the only location on Earth where ‘normal’ oceanic crust protrudes above sea level within the ocean basin in which it formed. This raises fundamental questions, including what facilitates the obduction of oceanic crust in this locality (crucial for fully understanding the context around much-studied ophiolite complexes such as the Samail, Oman), and the conditions which led to the largest strike-slip earthquake of the 20th Century (Mw 8.2; May 23 1989).

To begin to answer these questions, an array of broadband ocean-bottom and land seismometers was deployed on and around Macquarie Island between October 2020 and February 2022. In this presentation, we summarise the data that were collected – and challenges faced – and show a preliminary catalogue of microseismicity for the duration of the deployment, generated using QuakeMigrate software. QuakeMigrate uses a waveform-based approach to earthquake detection and location, with advantages including improved performance in the presence of heterogeneous noise sources, during intense seismic swarms with small inter-event times, and in automating the processing of large quantities of continuous seismic data. Sophisticated time-domain algorithms allow us to maintain an appropriate detection threshold despite strongly varying noise levels (in the world’s stormiest ocean), varying numbers of operational stations, and in the presence of significant clipping issues on the ocean-bottom instruments’ horizontal channels.

We search for temporal variations in earthquake rates, and compute relative relocations (using GrowClust software) to produce high-resolution images of the faults on which the seismicity occurs. These results are interpreted in the context of the location of the most recent large earthquakes on this segment of the plate boundary, and together with complementary geophysical parameters including geodetic measurements and submarine and subaerial fault mapping.

How to cite: Rawlinson, N., Winder, T., Tkalcic, H., Stock, J., and Coffin, M.: Microseismicity of the Macquarie Ridge Complex, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9886, https://doi.org/10.5194/egusphere-egu23-9886, 2023.