Structure of the Tasmanian lithosphere from 3-D seismic tomography

Nicholas Rawlinson, Hrvoje Tkalcic, Anya M. Reading

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Seismic data from three separate experiments, a marine active source survey with land-based stations, and two teleseismic arrays deployed to record distant earthquakes, are combined in a joint inversion for the 3D seismic structure of the Tasmanian lithosphere. In total, travel-time information from nearly 14 000 source-receiver paths are used to constrain a detailed model of crustal velocity, Moho geometry and upper mantle velocity beneath the entire island. Synthetic reconstruction tests show good resolution beneath most of Tasmania with the exception of the southwest, where data coverage is sparse. The final model exhibits a number of well-constrained features that have important ramifications for the interpretation of Tasmanian tectonic history. The most prominent of these is a marked easterly transition from lower velocity crust to higher velocity crust which extends from the north coast, northeast of the Tamar River, down to the east coast. Other significant anomalies include elevated crustal velocities beneath the Mt Read Volcanics and Forth Metamorphic Complex ; thickened crust beneath the Port Sorell and Badger Head Blocks in central northern Tasmania ; and distinctly thinner, higher velocity crust beneath the Rocky Cape Block in northwest Tasmania. Combined with existing evidence from field mapping, potential-field surveys and geochemical data, the new results support the contention that east and west Tasmania were once passively joined as far back as the Ordovician, with the transition from lithosphere of Proterozoic continental origin to Phanerozoic oceanic origin occurring some 50 km east of the Tamar River ; that the southeast margin of the Rocky Cape Block may have been a former site of subduction in the Cambrian ; and that the Badger Head and Port Sorell Blocks were considerably shortened and thickened during the Cambrian Tyennan and Middle Devonian Tabberabberan Orogenies.
Original languageEnglish
Pages (from-to)381-394
Number of pages14
JournalAustralian Journal of Earth Sciences
Volume57
Publication statusPublished - 2010

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seismic tomography
lithosphere
crust
coast
potential field
Phanerozoic
Moho
river
travel time
field survey
upper mantle
Ordovician
Proterozoic
seismic data
subduction
anomaly
geometry
earthquake
tectonics
history

Cite this

Rawlinson, N., Tkalcic, H., & Reading, A. M. (2010). Structure of the Tasmanian lithosphere from 3-D seismic tomography. Australian Journal of Earth Sciences, 57, 381-394.

Structure of the Tasmanian lithosphere from 3-D seismic tomography. / Rawlinson, Nicholas; Tkalcic, Hrvoje; Reading, Anya M.

In: Australian Journal of Earth Sciences, Vol. 57, 2010, p. 381-394.

Research output: Contribution to journalArticle

Rawlinson, N, Tkalcic, H & Reading, AM 2010, 'Structure of the Tasmanian lithosphere from 3-D seismic tomography', Australian Journal of Earth Sciences, vol. 57, pp. 381-394.
Rawlinson, Nicholas ; Tkalcic, Hrvoje ; Reading, Anya M. / Structure of the Tasmanian lithosphere from 3-D seismic tomography. In: Australian Journal of Earth Sciences. 2010 ; Vol. 57. pp. 381-394.
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AB - Seismic data from three separate experiments, a marine active source survey with land-based stations, and two teleseismic arrays deployed to record distant earthquakes, are combined in a joint inversion for the 3D seismic structure of the Tasmanian lithosphere. In total, travel-time information from nearly 14 000 source-receiver paths are used to constrain a detailed model of crustal velocity, Moho geometry and upper mantle velocity beneath the entire island. Synthetic reconstruction tests show good resolution beneath most of Tasmania with the exception of the southwest, where data coverage is sparse. The final model exhibits a number of well-constrained features that have important ramifications for the interpretation of Tasmanian tectonic history. The most prominent of these is a marked easterly transition from lower velocity crust to higher velocity crust which extends from the north coast, northeast of the Tamar River, down to the east coast. Other significant anomalies include elevated crustal velocities beneath the Mt Read Volcanics and Forth Metamorphic Complex ; thickened crust beneath the Port Sorell and Badger Head Blocks in central northern Tasmania ; and distinctly thinner, higher velocity crust beneath the Rocky Cape Block in northwest Tasmania. Combined with existing evidence from field mapping, potential-field surveys and geochemical data, the new results support the contention that east and west Tasmania were once passively joined as far back as the Ordovician, with the transition from lithosphere of Proterozoic continental origin to Phanerozoic oceanic origin occurring some 50 km east of the Tamar River ; that the southeast margin of the Rocky Cape Block may have been a former site of subduction in the Cambrian ; and that the Badger Head and Port Sorell Blocks were considerably shortened and thickened during the Cambrian Tyennan and Middle Devonian Tabberabberan Orogenies.

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