Ambient noise tomography of Australia: application to AusArray deployment

Abstract:

Over the past two decades, the use of seismic ambient noise has shown great potential in imaging the structure of the crust and lithospheric mantle. However, few datasets have been specifically collected to study mineral systems. Here, we present results from Geoscience Australia’s ‘AusArray’ deployment, acquired as part of the ‘Exploring for the Future’ program. This aimed to assess lithospheric structure and mineral system potential in undercover terranes, and comprised 120 portable broad-band stations installed across Northern Australia.

Using this data, we perform cross-correlation of background seismic noise, from which we extract Rayleigh wave dispersion curves. These allow us to image crustal structure between Tennant Creek and Mount Isa, and we present shear wave velocity maps at 4 - 30 s periods. Key features include: (i) A strong low-velocity anomaly (2.5 km/s) at ~2–4 km depth, delineating the outline of the newly-discovered Carrara sub-basin, prospective for hydrocarbons and base metals; and (ii) a near-vertical high-velocity anomaly (3.5 km/s) north of Mount Isa, extending from the near surface down to ~12 km and merging with northeast-trending anomalies, believed to reflect compositional variations within the mid-crust potentially associated with base metal deposits. All software to compute cross-correlations, estimate phase velocities and generate seismic tomography models is available through Geoscience Australia’s open-source software package, HiPerSeis, obtainable from https://github.com/GeoscienceAustralia/hiperseis.