A Probabilistic Shear Wave Velocity Model of the Crust in the Central West Australian Craton Constrained by Transdimensional Inversion of Ambient Noise Dispersion

摘要

The Capricorn Orogen in central Western Australia played important roles in initializing and finalizing the West Australian craton. Surface geological mapping and isotopic studies show that the crust has recorded over a billion years of tectonic history spanning from its crustal formation in the Archean to episodes of tectonothermal events during the Proterozoic cratonization processes. The region therefore provides us with an ideal laboratory to characterize the seismic signature associated with tectonic processes. We constructed a crustal shear wave velocity model of the core region of the orogen, the Glenburgh Terrane and its north boundary, by inverting the array group velocity dispersion data measured from a high-density temporary array. A modified Bayesian transdimensional tomography technique, which incorporates a smooth-varying regional reference velocity model and Moho topography, was used to invert for the crustal velocity variations. The inverted velocity model adds great detail to the intracrustal structure and provides complementary seismic velocity information to refine the regional tectonic processes. Distinct patterns in the velocity structure support that the Glenburgh Terrane is an Archean microcontinent and favor the role of Paleoproterozoic subductions/accretions during the assembly of the West Australian Craton.