Interactions of multi-scale heterogeneity in the lithosphere: Australia

Abstract

Understanding the complex heterogeneity of the continental lithosphere involves a wide variety of spatial scales and the synthesis of multiple classes of information. Seismic surface waves and multiply reflected body waves provide the main constraints on broad-scale structure, and bounds on the extent of the lithosphere-asthenosphere transition (LAT) can be found from the vertical gradients of S wavespeed. Information on finer-scale structures comes through body wave studies, including detailed seismic tomography and P-wave reflectivity extracted from stacked autocorrelograms of continuous component records. With the inclusion of deterministic large-scale structure and realistic medium-scale stochastic features fine-scale variations are subdued. The resulting multi-scale heterogeneity model for the Australian region gives a good representation of the character of observed seismograms and their geographic variations and matches the observations of P-wave reflectivity. P reflections in the 0.5-3.0 Hz band in the uppermost mantle suggest variations on vertical scales of a few hundred metres with amplitudes of the order of 1%. Interference of waves reflected or converted at sequences of such modest variations in physical properties produce relatively simple behaviour for lower

The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves

“…Observed layering in azimuthal anisotropy from surface waves occurs at depths that significantly differ from the observed Sp phases. Anisotropic layering may also be generated by changes in the small-scale heterogeneity structure of the lithospheric mantle, as observed by high frequency P coda waves (e.g., Kennett et al, 2017), although this cannot be distinguished using the lower frequency waveforms of this study. Elastically accommodated grain-boundary sliding (e.g., Karato et al, 2015) is invoked as a potential mechanism largely on the basis of how it would consistently produce a negative velocity gradient in the normal MLD depth range.…”

Insights Into Layering in the Cratonic Lithosphere Beneath Western Australia

“…The origin of multiple MLDs is currently unclear. Changes in the heterogeneous behavior could be a major contributor, as they could lead to variations in anisotropic properties and to wave interference that samples finer structures (Kennett & Furumura, ; Kennett et al, ). The existence of multiple MLDs might also be associated with lithospheric accretion via successive magmatic underplating or vertically stacked slabs with layered structures (e.g., Calò et al, ; Wirth & Long, ).…”

Lithospheric Architecture and Mantle Metasomatism Linked to Iron Oxide Cu‐Au Ore Formation: Multidisciplinary Evidence from the Olympic Dam Region, South Australia

“…Two data sets for the depth of the LAB were utilized, from Kennett et al (2013) and Czarnota et al (2013). The LAB of Kennett et al (2013) in the region of interest in South Australia corresponds quite closely to the lower bound of the lithosphere-asthenosphere transition zone described by Kennett et al (2017).…”