Crustal structure of the east Gondwana margin in southeast Australia revealed by transdimensional ambient seismic noise tomography

Abstract

Ambient seismic noise data from the ongoing WOMBAT transportable seismic array in southeast Australia, the largest deployment of its kind in the Southern Hemisphere, are used to produce a high‐resolution 3‐D shear wave velocity model of the region. We apply a two‐stage, transdimensional, hierarchical Bayesian inversion approach to recover phase velocity maps at periods of 1–20 s and then invert phase velocity dispersion for 3‐D shear wave velocity structure to the base of the crust. Data uncertainty is propagated through the sequence of inversions, ensuring that model complexity is justified by the quality and quantity of the measurements. The pattern of 3‐D velocity variations helps elucidate the geometry and position of key crustal features—such as the Torrens Hinge Zone—associated with the transition from Paleozoic eastern Australia to Precambrian central and western Australia that formed along the proto‐Pacific margin of east Gondwana.

Linking mainland Australia and Tasmania using ambient seismic noise tomography: Implications for the tectonic evolution of the east Gondwana margin

“…This concurs with previous interpretations using magnetic and gravity data (Cayley et al, 2002;McLean et al, 2010;Moore et al, 2013), and supports the interpretation of Proterozoic continental crust at least as far north as the Victorian coastline. Other tomography studies in Victoria (Rawlinson and Kennett, 2008;Rawlinson et al, 2011;Young et al, 2013a) and Tasmania (Rawlinson et al, 2006;Young et al, 2013b) have not recognised the presence of such a feature.…”

“…Since it was first demonstrated that Rayleigh wave energy emerges from the long-term crosscorrelation of background seismicity recorded by station pairs (Shapiro and Campillo, 2004), a cascade of remarkably detailed images of the crust have been obtained by exploiting this class of data Bensen et al, 2009;Saygin and Kennett, 2012;Young et al, 2013aYoung et al, , 2013b. Recent developments have allowed large scale features to be imaged at greater depth (Poli et al, 2012;Shen et al, 2013), and small scale features to be imaged near the surface (de Ridder and Biondi, 2013;Draganov et al, 2013).…”

“…average model, standard deviation of the ensemble) can be extracted. This approach has been shown to be far more robust than conventional tomography methods (Young et al, 2013a(Young et al, , 2013b. Results are interpreted in conjunction with information provided by potential field data, exploration wells, seismic reflection lines, geochemical analysis and field mapping.…”

On the use of sensitivity tests in seismic tomography

“…For example, Bayesian trans-dimensional tomography, in which the number of unknowns is an unknown itself, and the parametrization is adaptive, is starting to become increasingly popular. It has been shown to be computationally tractable for most 2-D and some 3-D problems (Bodin & Sambridge 2009;Bodin et al 2012;Young et al 2013;Galetti et al 2015;Piana Agostinetti et al 2015;Hawkins & Sambridge 2015), and generates a large ensemble of solutions which can be used to quantitatively assess solution reliability. In general, these methods have an intrinsic parsimony which results in a (variable) spatial resolution that contains only structure that is 'required' by the data; the uncertainty associated with structure at this spatial resolution can be estimated by taking the standard deviation of the solution ensemble.…”

Complex continental growth along the proto-Pacific margin of East Gondwana

“…To date, teleseismic body wave tomography (Rawlinson et al, 2014) and ambient noise tomography (Young et al, 2013) have been applied to yield isotropic three-dimensional (3-D) P wavespeed variations in the upper mantle and 3-D S wavespeed variations in the crust, respectively. canism, and identify different crustal provinces beneath younger cover.…”