Transdimensional ambient noise tomography of Bass Strait, southeast Australia, reveals the sedimentary basin and deep crustal structure beneath a failed continental rift

摘要: Debate is ongoing as to which tectonic model most consistent with the known geology of southeast Australia, formerly part eastern margin Gondwana. In particular, numerous models have been proposed explain enigmatic geological relationship between Tasmania and mainland, separated by Bass Strait. One primary reasons for lack certainty limited exposure basement rocks, are masked sea thick Mesozoic–Cenozoic sedimentary volcanic cover sequences. We use ambient noise tomography recorded across Strait generate a new shear wave velocity in order investigate crustal structure. Fundamental mode Rayleigh phase dispersion data extracted from long-term cross-correlation inverted using transdimensional, hierarchical, Bayesian inversion scheme produce maps period range 2–30 s. Subsequent depth-dependent structure dense grid points allows composite 3-D be produced. Benefits transdimensional include data-driven parametrization that number distribution unknowns vary, also treated an unknown inversion. The clearly reveals basins slow zones extend down 14 km depth. These failed rift basins, formed during early stages Australia–Antarctica break-up, appear overlying thinned crust, where high velocities 3.8–4.0 km s−1 occur at depths greater than 20 km. Along northern Strait, our major boundaries mapped surface. we identify east dipping transition zone vicinity Moyston Fault, boundary Lachlan Delamerian orogens, Phanerozoic accretionary terrane makes up Australia. A pronounced lineament (∼3.7–3.8 km s−1) lower crust may represent signature relict intrusive magmatism rifting break-up along scale discontinuity Selwyn Block microcontinent joins Victoria.