Crust and upper mantle structure beneath southeast Australia from ambient noise and teleseismic tomography

Rawlinson, Nicholas; Pilia, Simone; Young, Malin M.; Salmon, M.; Yang, Yingjie

doi:10.1016/j.tecto.2015.11.034

Cited by 33 publications

(62 citation statements)

References 65 publications

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“…A similar apparent correlation has been observed by Holford et al () primarily in the Flinders Range Seismic Zone in south Australia. Anomalous low seismic velocities are observed in the upper mantle beneath this region of high surface heat flow (Davies et al, ; Rawlinson et al, ), consistent with somewhat elevated Moho temperature and a mechanism involving weakening of the lower crust and upper mantle as Liu and Zoback () proposed for the New Madrid Seismic Zone (NMSZ).…”

Section: Discussionsupporting

confidence: 53%

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Attanayake

Sandiford

Schleicher³

et al. 2019

JGR Solid Earth

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Using a new seismic waveform data set, we locate 234 earthquakes and estimate source parameters (focal mechanisms, magnitude, and stress drop) of the two largest earthquakes (E1 and E2) in the 2012 seismic sequence in Thorpdale, Victoria. The focal mechanisms suggest thrust faulting, consistent with previous observations in southeast Australia. The estimated magnitudes are M w 4.9 ± 0.14 (E1) and 4.3 ± 0.1 (E2). The estimates of stress drop 57 ± 7.4 MPa (E1) and 28 ± 2.4 MPa (E2) reflect strength of faults in an intraplate environment. By analyzing spatiotemporal distribution of aftershocks, we show that E1 and E2 reflect two separate seismic sequences about a month apart. E1 and E2 ruptured two adjacent faults with orientations 218°/78°/78°(Fault 1) and 134°/27°/171°(Fault 2), respectively, where angles indicate strike/dip/slip rake. To test causal mechanism of fault interaction, we performed Coulomb stress modeling, which shows very weak unloading of E2 by E1. Thus, we infer that fault interaction might instead reflect remotely triggered fluid diffusion. Also, a local rotation of the stress field proceeding E1 might have favorably reoriented Fault 2 for failure. Finally, we identify an apparent correlation between high heat flow and seismicity in southeastern Australia, suggesting a combination of mechanisms including transient stress perturbations and lithospheric thermal weakening associated with high heat flow as the principal factors localizing intraplate seismicity.Plain Language Summary The 2012 earthquake sequence in Thorpdale is the most recent and significant seismic activity in southeast Australia, during which two moderate-sized earthquakes were felt in the region with the second earthquake thought to be an aftershock of the first. Using a newly assembled data set, we estimate source parameters of these earthquakes and locate 232 smaller earthquakes associated with this seismic sequence. In this study, we show that faults ruptured with thrust motion, the moment magnitude of the two largest earthquakes are 4.9 and 4.3, and the stress release per fault length (57 and 28 MPa) is larger than the global average. By locating aftershocks, we also show that the two largest earthquakes ruptured two separate faults rather than one. The absence of any plausible Coulomb stress loading suggests that these different faults interacted with each other through other mechanisms such as a fluid diffusion. Key Points:• The two largest earthquakes (M w 4.9 and 4.3) in the seismic sequence indicate thrust faulting in southeast Australia • Higher than average stress drop (57 and 28 MPa) suggests the rupture of strong faults with longer recurrence intervals • Adjacent fault planes ruptured, implying fault interaction through interplay between stress conditions and fluid diffusion Supporting Information:• Supporting Information S1

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Section: Discussionsupporting

confidence: 53%

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Attanayake

Sandiford

Schleicher³

et al. 2019

JGR Solid Earth

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“…Clustering of volcanic features on a large scale is generally interpreted to be an indication of the geological structures in the subsurface, such as the location and shape of the underlying magma source [e.g., Brenna et al ., ] and/or the (elastic) thickness of the underlying lithosphere [ Vogt , ; Mohr and Wood , ; Mazzarini , ]. Geophysical imaging [ Fishwick et al ., ; Davies and Rawlinson , ; Rawlinson et al ., ] has shown that the lithosphere in southeast Australia has a complex 3‐D thickness configuration, caused by the stacking of both continental and oceanic crustal fragments in the Delamerian and Lachlan fold belts, as well as the incorporation of exotic crustal blocks such as the Selwyn Block [ Cayley , ; Cayley et al ., ]. Magneto‐telluric sounding has shown that distinct regions of partial melt are currently present in the upper mantle below the NVP [ Aivazpourporgou et al ., ], spatially overlapping with our Central Highlands and Western Plains East clusters, but not with the Mt Gambier and Western Plains East cluster.…”

Section: Discussionmentioning

confidence: 99%

“…The distinct major and trace element and isotope signatures [ Oostingh et al ., ], U‐Th disequilibria [ Demidjuk et al ., ], and geophysical data [ Davies and Rawlinson , ] of the NVP basalts are best explained by the geodynamic model of edge‐driven convection [ King and Anderson , ] aided by shear‐driven upwelling [ Conrad et al ., ], resulting in localized upwelling of shallow mantle at the trailing edge of an anomalous thick block of lithosphere (Figure a). It is still possible that the age progression is caused by a migrating roll of fertile mantle material from east to west, caused by an east to west motion of the shallow mantle during shear‐assisted upwelling caused by the complex 3‐D lithospheric thickness variations below the NVP [ Fishwick et al ., ; Rawlinson et al ., ] during edge‐driven convection. In such a scenario, one would expect that such a fertile mantle patch is now located in the west, at the approximate location of the youngest volcanism.…”

Section: Spatiotemporal Constraints On Nvp Volcanismmentioning

confidence: 99%

⁴⁰Ar/³⁹Ar geochronology reveals rapid change from plume‐assisted to stress‐dependent volcanism in the Newer Volcanic Province, SE Australia

Oostingh

Jourdan

Matchan

et al. 2017

Geochem Geophys Geosyst

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Here we present 40Ar/39Ar ages of volcanic features in the Cenozoic intraplate Newer Volcanic Province in southeast Australia. The <5 Ma volcanic products in the Newer Volcanic Province can be subdivided into tholeiitic, valley‐filling Newer Plains basalts, and alkaline scoria cones, lava shields, and maars of the Newer Cones series. Plateau ages range from 3.76 ± 0.01 to 4.32 ± 0.03 Ma (2σ; all sources of uncertainties included) for the Newer Plains series, with production rates of volcanism decreasing post 4 Ma. We suggest that magmatism is related to the complex interplay of magma upwelling due to edge‐driven convection and the Cosgrove track mantle plume located in the northeast of the province at 6.5–5 Ma. Plateau ages range from 1290 ± 20 to 41.1 ± 2.2 ka (2σ) for the Newer Cones series, with a diffuse age progression in the onset of volcanism for these features from east to west. Analyses of the distribution and geomorphology of these volcanic features indicates a strong control of basement faults on volcanism, reflected in alignment of volcanic features along Paleozoic north‐south oriented basement faults in the east and Cretaceous northwest‐southeast oriented extensional features in the west. This age progression can be explained by a westerly migration of stress derived from the left‐lateral strike‐slip Tasman Fracture Zone. This suggests that the general mechanism of volcanism changed from upwelling due to plume‐assisted edge‐driven convection prior to ∼4 Ma to stress‐dependent upwelling at around 1.3 Ma.

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“…To date, 17 sequential deployments have resulted in coverage of the entire Lachlan and Delamerian orogens and parts of the Thomson and New England orogens (see Figure for orogen locations) at a station spacing of approximately 50 km (see Figure S1 in the supporting information). This has allowed high‐resolution teleseismic body wave [ Rawlinson et al , , , ] and ambient noise surface wave [ Young et al , ; Rawlinson et al , ; Pilia et al , ] tomography to be carried out in order to image the crust and upper mantle. In the results and discussion that follow, we use the latest WOMBAT seismic tomography, combined with numerical modeling of mantle flow, to quantitatively examine the mechanisms underpinning Cenozoic intraplate volcanism in eastern Australia.…”

Section: Introductionmentioning

confidence: 99%

The mechanisms underpinning Cenozoic intraplate volcanism in eastern Australia: Insights from seismic tomography and geodynamic modeling

Rawlinson

Davies

Pilia

2017

Geophysical Research Letters

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Cenozoic intraplate volcanism is widespread throughout much of eastern Australia and manifests as both age‐progressive volcanic tracks and non‐age‐progressive lava fields. Various mechanisms have been invoked to explain the origin and distribution of the volcanism, but a broad consensus remains elusive. We use results from seismic tomography to demonstrate a clear link between lithospheric thickness and the occurrence, composition, and volume of volcanic outcrop. Furthermore, we find that non‐age‐progressive lava fields overlie significant cavities in the base of the lithosphere. Based on numerical simulations of mantle flow, we show that these cavities generate vigorous mantle upwellings, which likely promote decompression melting. However, due to the intermittent nature of the lava field volcanics over the last 50 Ma, it is probable that transient mechanisms also operate to induce or enhance melting. In the case of the Newer Volcanics Province, the passage of a nearby plume appears to be a likely candidate. Our results demonstrate why detailed 3‐D variations in lithospheric thickness, plate motion, and transient sources of mantle heterogeneity need to be considered when studying the origin of non age‐progressive volcanism in continental interiors.

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Crust and upper mantle structure beneath southeast Australia from ambient noise and teleseismic tomography

Cited by 33 publications

References 65 publications

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

⁴⁰Ar/³⁹Ar geochronology reveals rapid change from plume‐assisted to stress‐dependent volcanism in the Newer Volcanic Province, SE Australia

The mechanisms underpinning Cenozoic intraplate volcanism in eastern Australia: Insights from seismic tomography and geodynamic modeling

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Crust and upper mantle structure beneath southeast Australia from ambient noise and teleseismic tomography

Cited by 33 publications

References 65 publications

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

Interacting Intraplate Fault Systems in Australia: The 2012 Thorpdale, Victoria, Seismic Sequences

40Ar/39Ar geochronology reveals rapid change from plume‐assisted to stress‐dependent volcanism in the Newer Volcanic Province, SE Australia

The mechanisms underpinning Cenozoic intraplate volcanism in eastern Australia: Insights from seismic tomography and geodynamic modeling

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⁴⁰Ar/³⁹Ar geochronology reveals rapid change from plume‐assisted to stress‐dependent volcanism in the Newer Volcanic Province, SE Australia