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  • Articles  (208)
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  • 1
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    The lithosphere-asthenosphere transition and radial anisotropy beneath the Australian continent (2015)
    Wiley
    Details
    Publication Date: 2015-05-07
    Description: A new 3-D S wavespeed model for the Australian region derived from multi-mode surface waves allows us to examine the nature of the lithosphere-asthenosphere transition (LAT) and its relation to radial anisotropy. In eastern Phanerozoic Australia the estimated depths of the LAT tie well with those from receiver functions. However, in the Archean and Proterozoic lithosphere in western and central Australia, the LAT derived from the surface wave model is generally much deeper than the discontinuities recognized from receiver functions, and shows a smooth transition. There is significant radial anisotropy (SH〉SV) in the upper lithosphere as well as in the LAT and the underlying asthenosphere. Strong anisotropy in the asthenosphere reflects the effects of present shear flow in the mantle beneath the continent. The lateral variation of lithospheric anisotropy correlates well with the suture zones between cratonic blocks, representing frozen anisotropy associated with the ancient tectonics of Australia.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Receiver structure from teleseisms: auto- and cross-correlation (2016)
    Wiley
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    Publication Date: 2016-06-14
    Description: We present a way of characterizing the structure beneath a seismic station, by exploiting stacked correlograms of three-component records from teleseismic events. This seismic daylight imaging approach exploits the extraction of reflection and conversion information from teleseismic coda via tensor auto-correlation. The approach is illustrated for a number of Australian stations in a variety of tectonic environments using hundreds of teleseismic events, to extract P - and S - reflectivity and converted Ps and Sp information. The results show very good agreement with prior knowledge across Australia. Compared with the classical receiver function, the broader frequency band of 0.5–4.0 Hz provides additional information on finer scale structure.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    AusMoho: the variation of Moho depth in Australia (2011)
    Oxford University Press
    Details
    Publication Date: 2011-09-24
    Description: SUMMARY Since 2004 more than 7000 km of full-crustal reflection profiles have been collected across Australia to give a total of more than 11 000 km, providing valuable new constraints on crustal structure. A further set of hitherto unexploited results comes from 150 receiver functions distributed across the continent, mostly from portable receiver sites. These new data sets provide a dramatic increase in data coverage compared with previous studies, and reveal the complex structure of the Australian continent in considerable detail. A new comprehensive model for Moho depth across Australia and its immediate environment is developed by utilizing multiple sources of information. On-shore and off-shore refraction experiments are supplemented by receiver functions from a large number of portable stations and the recently augmented set of permanent stations, and Moho picks from the full suite of reflection transects. The composite data set provides a much denser sampler of most of the continent than before, though coverage remains low in the remote areas of the Simpson and Great Sandy deserts. The various data sets provide multiple estimates of the depth to Moho in many regions and the consistency between the different techniques is high. In a number of instances, differences in estimates of Moho depth can be associated with the aspects of the structure highlighted by the particular methods. The new results allow considerable refinement of the patterns of Moho depth across the continent. Some of the thinnest crust lies beneath the Archean cratons in the Pilbara and the southern part of the Yilgarn. Thick crust is encountered beneath parts of the Proterozoic in Central Australia, and beneath the Palaeozoic Lachlan fold belt in southeastern Australia. The refined data indicate a number of zones of sharp contrast in depth to Moho, notably in the southern part of Central Australia.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 4
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    Crustal structure of Australia from ambient seismic noise tomography (2012)
    Wiley
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    Publication Date: 2012-01-07
    Description: Surface wave tomography for Australian crustal structure has been carried out using group velocity measurements in the period range 1–32 s extracted from stacked correlations of ambient noise between station pairs. Both Rayleigh wave and Love wave group velocity maps are constructed for each period using the vertical and transverse component of the Green's function estimates from the ambient noise. The full suite of portable broadband deployments and permanent stations on the continent have been used with over 250 stations in all and up to 7500 paths. The permanent stations provide a useful link between the various shorter-term portable deployments. At each period the group velocity maps are constructed with a fully nonlinear tomographic inversion exploiting a subspace technique and the Fast Marching Method for wavefront tracking. For Rayleigh waves the continental coverage is good enough to allow the construction of a 3D shear wavespeed model in a two stage approach. Local group dispersion information is collated for a distribution of points across the continent and inverted for a 1D SV wavespeed profile using a Neighbourhood Algorithm method. The resulting set of 1D models are then interpolated to produce the final 3D wavespeed model. The group velocity maps show the strong influence of thick sediments at shorter periods, and distinct fast zones associated with cratonic regions. Below the sediments the 3D shear wavespeed model displays significant heterogeneity with only moderate correlation with surface tectonic features. For example, there is no evident expression of the Tasman Line marking the eastern edge of Precambrian outcrop. The large number of available inter-station paths extracted from the ambient noise analysis provide detailed shear wavespeed information for crustal structure across the Australian continent for the first time, including regions where there was no prior sampling because of difficult logistics.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Uppermost mantle structure beneath eastern China and its surroundings from Pn and Sn tomography (2016)
    Wiley
    Details
    Publication Date: 2016-03-15
    Description: The Pn and Sn residuals from regional events provide strong constraints on the structure and lithological characteristics of the uppermost mantle beneath eastern China and its surroundings. With the dense Chinese Digital Seismic Network in eastern China, separate Pn and Sn tomographic inversions have been exploited to obtain P and S velocities at a resolution of 2 ∘ ×2 ∘ or better. The patterns of P velocities are quite consistent with the S velocities at depth of 50 and 60 km, but the amplitude of P wavespeed anomalies are a little larger than those of S wavespeed. The low P wavespeed, high S wavespeed and low V p / V s ratio beneath the northern part of Ordos Basin is related to upwelling hot material. Abrupt changes in material properties are indicated from the rapid variations in the V p / V s ratio.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Probabilistic surface reconstruction from multiple data sets: An example for the Australian Moho (2012)
    Wiley
    Details
    Publication Date: 2012-10-19
    Description: Interpolation of spatial data is a widely used technique across the Earth sciences. For example, the thickness of the crust can be estimated by different active and passive seismic source surveys, and seismologists reconstruct the topography of the Moho by interpolating these different estimates. Although much research has been done on improving the quantity and quality of observations, the interpolation algorithms utilized often remain standard linear regression schemes, with three main weaknesses: (1) the level of structure in the surface, or smoothness, has to be predefined by the user; (2) different classes of measurements with varying and often poorly constrained uncertainties are used together, and hence it is difficult to give appropriate weight to different data types with standard algorithms; (3) there is typically no simple way to propagate uncertainties in the data to uncertainty in the estimated surface. Hence the situation can be expressed by Mackenzie (2004): “We use fantastic telescopes, the best physical models, and the best computers. The weak link in this chain is interpreting our data using 100 year old mathematics”. Here we use recent developments made in Bayesian statistics and apply them to the problem of surface reconstruction. We show how the reversible jump Markov chain Monte Carlo (rj-McMC) algorithm can be used to let the degree of structure in the surface be directly determined by the data. The solution is described in probabilistic terms, allowing uncertainties to be fully accounted for. The method is illustrated with an application to Moho depth reconstruction in Australia.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Mid-lithosphere discontinuities beneath the western and central North China Craton (2017)
    Wiley
    Details
    Publication Date: 2017-01-31
    Description: By analyzing P reflectivity extracted from stacked autocorrelograms for teleseismic events on a dense seismic profile, we obtain a detailed image of the mid-lithosphere discontinuity (MLD) beneath western and central North China Craton (NCC). This seismic daylight imaging exploits a broad high-frequency band (0.5–4 Hz) to reveal the fine-scale component of multi-scale lithospheric heterogeneity. The depth of the MLD beneath the western and central parts of the NCC ranges 80–120 km, with a good match to the transition to negative S velocity gradient with depth from Rayleigh wave tomography. The MLD inferred from SDI also has good correspondence with the transition from conductive to convective regimes estimated from heat-flow data indicating likely thermal control within the seismological lithosphere.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    The inversion of surface wave data (1976)
    Springer
    Pure and applied geophysics 114 (1976), S. 747-751 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Observations of surface waves depend both on the structure traversed and the nature of the source, and therefore inversion of surface wave data can yield information about both structure and sources. The available methods for structural inversion are compared and discussed and a suggestion made for improved source inversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875784
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  • 9
    Electronic Resource
    Electronic Resource
    The influence of lateral variations on seismic refraction interpretation (1976)
    Springer
    Pure and applied geophysics 114 (1976), S. 647-652 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The effects of unsuspected lateral variation in seismic velocities at depth on the interpretation of a seismic refraction profile are discussed with the aid of a numerical experiment. The results show that there will be bias in any velocity depth models derived by travel time analysis based on the assumption of horizontally layered media. This bias is examined for a lithospheric profile using both extremal and linearised travel time inversion. In addition quite mild subsurvace topography can have an appreciable effect on the amplitude distribution along the profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875658
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  • 10
    Electronic Resource
    Electronic Resource
    Earth science Roots of the matter (2003)
    [s.l.] : Nature Publishing Group
    Nature 422 (2003), S. 674-675 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Over the past three decades there has been vigorous debate over how thick the continents can be — that is, the depth to which the rigid crust and upper mantle reach before meeting convecting mantle that can flow and drive tectonic motion. On page 707 of this issue, Gung and colleagues ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/422674a
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