Crustal structure of southeast Australia from teleseismic receiver functions
In an effort to improve our understanding of southeast Australia’s enigmatic tectonic evolution, we analyse teleseismic earthquakes recorded by 24 temporary and 8 permanent broadband stations using the receiver function method. Crustal thickness, bulk seismic velocity and internal crustal structure...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/se-2020-74 https://se.copernicus.org/preprints/se-2020-74/ |
| Summary: | In an effort to improve our understanding of southeast Australia’s enigmatic tectonic evolution, we analyse teleseismic earthquakes recorded by 24 temporary and 8 permanent broadband stations using the receiver function method. Crustal thickness, bulk seismic velocity and internal crustal structure of the southern Tasmanides – an assemblage of Palaeozoic accretionary orogens that occupy eastern Australia – are constrained by our new results which point to: (1) a 39.0 ± 0.5 km thick crust, a relatively high Poisson’s ratio (0.262 ± 0.014) and a broad (> 10 km) crust-mantle transition beneath the Lachlan Fold Belt. This is interpreted to represent magmatic underplating of mafic materials at the base of the crust; (2) a complex crustal structure beneath VanDieland, a postulated Precambrian continental fragment embedded in the southernmost Tasmanides, where the crust thickens (37.5 ± 1.2 km) towards the northern tip of the microcontinent as it enters south central Victoria but thins south into Bass Strait (30.5 ± 2.1 km), before once again becoming thicker beneath western Tasmania (33.5 ± 1.9 km). The thinner crust beneath Bass Strait can be attributed to lithospheric stretching that resulted from the break-up of Antarctica and Australia and the opening of the Tasman Sea; (3) stations located in the East Tasmania Terrane and eastern Bass Strait (ETT+EB) collectively indicate crust of uniform thickness (∼ 33 km) and a slightly broad Moho transition that reflect a possible underplating event associated with a Palaeozoic subduction system. The relative uniformity of V p /V s and Poisson’s ratio in VanDieland – suggesting uniformity in composition – could be used in support of the VanDieland microcontinental model that explains the tectonic evolution of southeast Australia. |
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