Crustal structure of southeast Australia from teleseismic receiver functions

Mohammed Bello, Dave G Cornwell, Nicholas Rawlinson, Anya M. Reading, Othaniel K. Likkason

Research output: Contribution to journalArticlepeer-review

Abstract

In an effort to improve our understanding of the seismic character of the crust beneath southeast Australia, and how it relates to the tectonic evolution of the region, we analyse teleseismic earthquakes recorded by 24 temporary and 8 permanent broadband stations using the receiver function method. Due to the proximity of the temporary stations to Bass Strait, only 13 of these stations yielded usable receiver functions, whereas seven permanent stations produced receiver functions for subsequent analysis. Crustal thickness, bulk seismic velocity properties and internal crustal structure of the southern Tasmanides – an assemblage of Palaeozoic accretionary orogens that occupy eastern Australia – are constrained by H-κ stacking and receiver functionκ stacking and receiver function inversion, which point to: (1) a ~39.0 km thick crust, an intermediate-κ stacking and receiver functionhigh Vp/Vs ratio (~1.70-κ stacking and receiver function1.76), relative to ak135, and a broad (>10 km) crust-κ stacking and receiver functionmantle transition beneath the Lachlan Fold Belt. These results are interpreted to represent magmatic underplating of mafic materials at the base of the crust; (2) a complex crustal structure beneath VanDieland, a putative Precambrian continental fragment embedded in the southernmost Tasmanides, which features strong variability in crustal thickness (23-κ stacking and receiver function37 km) and Vp/Vs ratio (1.65-κ stacking and receiver function193), the latter of which likely represents compositional variability and the presence of melt. The complex origins of VanDieland, which comprises multiple continental ribbons, coupled with recent failed rifting and intraplate volcanism, likely contributes to these observations; and (3) stations located in the East Tasmania Terrane and Eastern Bass Strait (ETT+EB) collectively indicate crust of uniform thickness (31-κ stacking and receiver function32 km), which clearly distinguish it from VanDieland to the west. Moho depths are also compared with the continent-κ stacking and receiver functionwide AusMoho model in southeast Australia, and are shown to be largely consistent, except in regions where AusMoho has few constraints (e.g. Flinders Island). A joint interpretation of the new results with ambient noise, teleseismic tomography and teleseismic shear wave splitting anisotropy, helps provide new insight into the way that the crust has been shaped by recent events, including failed rifting during the break-κ stacking and receiver functionup of Australia and Antarctica and recent intraplate volcanism.
Original languageEnglish
Pages (from-to)463-481
Number of pages19
JournalSolid earth
Volume12
Issue number2
DOIs
Publication statusPublished - 24 Feb 2021

Keywords

  • receiver functions
  • crustal structure
  • VanDieland
  • Bass Strait
  • SE Australia

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