WA Array Phase 1 data release from the South West

WA Array is a 10-year program to install a network of seismometers across Western Australia. Starting in 2022, this $30 million initiative is funded by the WA Government and run by the Geological Survey of Western Australia (GSWA).

The project involves deploying 165 seismometers, spaced at 40km intervals, in a grid pattern. The entire State will be mapped by relocating the instruments annually between nine regional areas, the first of which was the South West. The objective is to monitor naturally occurring vibrations within the Earth, such as earthquakes, ocean waves and anthropogenic activities, to determine the composition and structure of the Earth’s crust and deeper lithosphere.

The data will help geoscientists better define areas of higher prospectivity under deep cover, evaluate future competing land uses, mitigate seismic hazards and maximise WA’s opportunities in the transition to net-zero emissions. WA Array is building on similar surveys across the rest of Australia, but with higher density data collection leading to more detailed images and models.

The program is a major logistical undertaking, representing one of the largest and highest resolution passive seismic projects completed anywhere in the world. When completed, WA will have the best 3D-imaged lithosphere in the world, making it an ideal natural laboratory to study the geological processes that have shaped the lithosphere and distributed its resources.

The 12-month data collection for Phase 1 in the South West of WA was completed in December 2023. The waveform data is now freely available on AusPass, the national Australian Passive Seismic Server. The first previews of the processed results and models from Phase 1 were released at the GSWA Open Day in Perth on 15 November, and are now available through MAGIX. The final report will be published on eBookshop by the end of December.

State-of-the-art models derived from the data include:

• A local seismicity catalogue.
• Vp and Vs crustal models derived from local earthquakes.
• Crustal Vs models derived from ambient noise tomography.
• Vs30 models and depth to basement.
• Moho depths from receiver function analysis.
• Bulk crustal composition.
• Mantle anisotropy.
• Bodywave tomography imaging the lithosphere.
• Surface wave tomography imaging the lithosphere–asthenosphere boundary.