Seismic and mechanical anisotropy and the past and present deformation of the Australian lithosphere

Simons, Frederik J.; Hilst, R. D. van der

doi:10.1016/s0012-821x(03)00198-5

Cited by 70 publications

(50 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fast anisotropy directions beneath Australia do not correlate with APM at depths shallower than 150 km, but show strong correlation from 150 km to 300 km depth with a maximum near 200 km. This agrees with previous regional surface wave tomography for the continent [10][11][12][13] . None of the other continents show significant plate-scale correlation between anisotropic directions and APM.…”

supporting

confidence: 92%

Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia

Debayle

Kennett

Priestley

2005

Nature

258

277

View full text Add to dashboard Cite

International audienceDifferences in the thickness of the high-velocity lid underlying continents as imaged by seismic tomography, have fuelled a long debate on the origin of the 'roots' of continents(1-5). Some of these differences may be reconciled by observations of radial anisotropy between 250 and 300 km depth, with horizontally polarized shear waves travelling faster than vertically polarized ones(2). This azimuthally averaged anisotropy could arise from present-day deformation at the base of the plate, as has been found for shallower depths beneath ocean basins(6). Such deformation would also produce significant azimuthal variation, owing to the preferred alignment of highly anisotropic minerals(7). Here we report global observations of surface-wave azimuthal anisotropy, which indicate that only the continental portion of the Australian plate displays significant azimuthal anisotropy and strong correlation with present-day plate motion in the depth range 175 - 300 km. Beneath other continents, azimuthal anisotropy is only weakly correlated with plate motion and its depth location is similar to that found beneath oceans. We infer that the fast-moving Australian plate contains the only continental region with a sufficiently large deformation at its base to be transformed into azimuthal anisotropy. Simple shear leading to anisotropy with a plunging axis of symmetry may explain the smaller azimuthal anisotropy beneath other continents

show abstract

supporting

confidence: 92%

Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia

Debayle

Kennett

Priestley

2005

Nature

258

277

View full text Add to dashboard Cite

show abstract

“…However, both differ markedly from the solution of Simons and van der Hilst [2003], which we suspect is in error.…”

Section: C3 Equivalent Topography Approximationmentioning

confidence: 65%

“…(a) Its variation as a function of T e for f = 1 and (b) its variation as a function of f for T e = 40 km. Red curves show the solutions from the quartic equation, green curves are from Simons and van der Hilst [2003], and blue curves are from numerical interpolation of the theoretical coherence formula. The black curve shows the flexural wavelength given by Macario et al [1995], which is f-independent.…”

Section: C3 Equivalent Topography Approximationmentioning

confidence: 99%

An accuracy assessment of the fan wavelet coherence method for elastic thickness estimation

Kirby

Swain

2008

Geochem Geophys Geosyst

107

View full text Add to dashboard Cite

[1] A variety of methods exist to estimate the elastic thickness (T e ) of the lithosphere. In this contribution, we attempt to provide an indication of how well the fan wavelet coherence method recovers T e , through synthetic modeling. The procedure involves simulating initial topographic and subsurface loads and emplacing them on a thin elastic plate of known T e , generating the postloading topography and gravity. We then attempt to recover that T e distribution from the gravity and topography through the wavelet method, hence discovering where its strengths and weaknesses lie. The T e distributions we use here have elliptical and fractal geometries, while the initial loads are fractal. Importantly, we have found that this widely used synthetic loading calibration method will tend to result in underestimates of T e no matter which recovery method is used. This is due to random correlations between the initial loads which, on average, serve to increase their coherence at all wavelengths and spatial locations. For the fan wavelet method, the degree of underestimation from this ''background'' source is approximately 10% of the true T e . In addition, the fan wavelet coherence method will provide underestimates of (1) the true T e when the study area size is of the order of the highest flexural wavelength or less, (2) relative T e differences when the T e anomaly is narrow compared to its flexural wavelength, and (3) steep T e gradients. Significantly, we find that the recovery is not greatly affected by the assumption of uniform T e in the inversion of the coherence. We also find that T e recovery from the coherence is only weakly dependent upon the initial subsurface-to-surface loading ratio ( f ). In contrast to the coherence, T e recovery from the admittance is highly ''noisy,'' with discontinuities and overestimates of T e frequently arising. This is most likely due to the high sensitivity of the admittance to f and is likely to apply to real data as well.

show abstract

“…reviews by Silver, 1996 andSavage, 1999) and it is clear that in some continental regions contributions from both must be considered (e.g., Simons and van der Hilst, 2003). We cannot rule out contributions from the lithosphere, but for the current presentation of the results we assume that asthenospheric anisotropy contributes significantly to splitting observed at F-net.…”

Section: Is Anisotropy Located Primarily In the Lithosphere Or The Asmentioning

confidence: 97%

Upper mantle anisotropy beneath Japan from shear wave splitting

Long

Hilst

2005

Physics of the Earth and Planetary Interiors

Self Cite

135

151

View full text Add to dashboard Cite

In this study, we utilize data from 64 broadband seismic stations of the Japanese F-net network to investigate the threedimensional pattern of anisotropy in the subduction system beneath Japan. We have compiled a database of approximately 1900 high-quality splitting measurements, selected by visual inspection of over 25,000 records of S, SKS, and SKKS phases at F-net stations, covering a wide range of incidence angles, incoming polarization angles, and backazimuths. Analysis of the variations of measured splitting parameters with these parameters allows us to consider complexities in structure such as multiple anisotropic layers, dipping symmetry axes, and small-scale lateral variations in anisotropic properties. Here we focus on the presentation of the splitting measurements themselves; a detailed interpretation in terms of tectonics and mantle flow is beyond the scope of this paper.In the southern part of the F-net array, along the Ryukyu arc, we find that fast directions are consistently trench-parallel, with splitting times of 1 s or more. Moving northward along the array, the measured splitting patterns become more complicated, with significant variations in apparent splitting parameters that indicate complex anisotropic structure. Additionally, measured fast directions vary significantly over short length scales, and stations separated by less than 100 km often exhibit very different splitting behavior. This increase in complexity of anisotropic structure coincides geographically with the complicated slab morphology of the subducting Pacific plate. At stations on Hokkaido, to the north, and Kyushu, to the south, we see some evidence that the fast direction of anisotropy may rotate from trench-parallel close to the trench to subduction-parallel further away from the trench, which may correspond either to a change in stress conditions and/or volatile content, or to a change in flow regime.

show abstract

Seismic and mechanical anisotropy and the past and present deformation of the Australian lithosphere

Cited by 70 publications

References 71 publications

Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia

Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia

An accuracy assessment of the fan wavelet coherence method for elastic thickness estimation

Upper mantle anisotropy beneath Japan from shear wave splitting

Contact Info

Product

Resources

About