The geological structure of southwest Australia is complex and has a rich history of Precambrian cratonization and Phanerozoic continental breakup. This region is dominated by the Archean Yilgarn Craton, but its tectonic evolution has been a subject of controversy for over a century. Recent work by the Geological Survey of Western Australia has refined the terrane boundary between the South West Terrane and the Youanmi Terrane and has added geological context to mineral deposits in the southwest Yilgarn Craton. The Southwest Australia Seismic Network (SWAN) is a new temporary broadband network of 27 stations that has been deployed since July 2020 to record earthquakes for seismic hazard applications and to improve the rendering of 3-D seismic structure in the crust and mantle lithosphere of southwest Australia (Miller et al., 2023). Using continuous data recorded by the SWAN and nearby stations, this study has produced a new 3-D shear wave velocity model in the crust and uppermost mantle using ambient noise tomography. Preliminary images show relatively high-velocity anomalies in the crust of the Yilgarn Craton and distinct low-velocity anomalies beneath the Perth Basin in the west, separated by the strong velocity contrast along the N-S trending Darling Fault. In the southwest Yilgarn Craton, we detect a prominent velocity contrast between the South West Terrane and the Youanmi Terrane in the lower crust to the uppermost mantle, which roughly coincides with the refined terrane boundary. These initial results are being integrated with other geophysical, geochemical and geological information to improve understanding of the unusual intra-plate seismic activity and the geological history of the Archean Yilgarn Craton.

Reference(s)

Miller, M. S., Pickle, R., Murdie, R., Yuan, H., Allen, T. I., Gessner, K., ... & Whitney, J. (2023). Southwest Australia Seismic Network (SWAN): Recording Earthquakes in Australia’s Most Active Seismic Zone. Seismological Research Letters.