Quasi-Love wave scattering reveals tectonic history of Australia and its margins reflected by mantle anisotropy

The Australian continental crust preserves a rich geological history, but it is unclear to what extent this history is expressed deeper within the mantle. Here an investigation of Quasi-Love waves is performed to detect scattering of seismic surface waves at mantle depths (between 100–200 km) by lateral gradients in seismic anisotropy. Across Australasia 275 new observations of Quasi-Love waves are presented. The inferred scattering source and lateral anisotropic gradients are preferentially located either near the passive continental margins, or near the boundaries of major geological provinces within Australia. Pervasive fossilized lithospheric anisotropy within the continental interior is implied, on a scale that mirrors the crustal geology at the surface, and a strong lithosphere that has preserved this signal over billions of years. Along the continental margins, lateral anisotropic gradients may indicate either the edge of the thick continental lithosphere, or small-scale dynamic processes in the asthenosphere below. Quasi-Love wave scattering is used to identify gradients in seismic anisotropy in the mantle beneath Australia that may represent major lithospheric boundaries between geological provinces and modified mantle flow along the ocean-continent transition.