Elastic thickness and isostatic coherence anisotropy in the South Indian Peninsular Shield and its implications

Stephen, Jimmy; Singh, S. B.; Yedekar, D. B.

doi:10.1029/2003gl017686

Cited by 21 publications

(7 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, directions aligned with significant anisotropy in the topography or gravity data may also be spurious. A conservative global reanalysis of gravity-topography coherence on these terms, which we present in the Supplementary Material, produces only scant evidence for lithospheric flexural anisotropy, in marked contrast to previous results (Rajesh et al, 2003;Stephen et al, 2003;Nair et al, 2011Nair et al, , 2012Zamani et al, 2013). We draw attention particularly to the results reported by Audet and Bürgmann (2011), which we feel are in danger of being over-interpreted.…”

Section: Discussioncontrasting

confidence: 52%

“…First applied to the Australian continent and the Canadian Shield, these methods have since yielded apparent evidence for pervasive mechanical anisotropy worldwide (Rajesh et al, 2003;Stephen et al, 2003;Nair et al, 2011Nair et al, , 2012Zamani et al, 2013). Audet and Bürgmann (2011) made a geologically attractive case for tectonic inheritance being a controlling factor in the deformation behaviour of the lithosphere throughout supercontinent cycles.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis

Kalnins

Simons

Kirby

et al. 2015

Earth and Planetary Science Letters

View full text Add to dashboard Cite

Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Earth and Planetary Science Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractLithospheric strength variations both influence and are influenced by many tectonic processes, including orogenesis and rifting cycles. The long, complex, and highly anisotropic histories of the continental lithosphere might lead to a natural expectation of widespread mechanical anisotropy. Anisotropy in the coherence between topography and gravity anomalies is indeed often observed, but whether it corresponds to an elastic thickness that is anisotropic remains in question. If coherence is used to estimate flexural strength of the lithosphere, the null-hypothesis of elastic isotropy can only be rejected when there is significant anisotropy in both the coherence and the elastic strengths derived from it, and if interference from anisotropy in the data themselves can be plausibly excluded. We consider coherence estimates made using multitaper and wavelet methods, from which estimates of effective elastic thickness are derived. We develop a series of statistical and geophysical tests for anisotropy, and specifically evaluate the potential for spurious results with synthetically generated data. Our primary case study, the North American continent, does not exhibit meaningful anisotropy in its mechanical strength. Similarly, a global reanalysis of continental gravity and topography using multitaper methods produces only scant evidence for lithospheric flexural anisotropy.

show abstract

Section: Discussioncontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis

Kalnins

Simons

Kirby

et al. 2015

Earth and Planetary Science Letters

View full text Add to dashboard Cite

show abstract

“…Authors using mirroring with Fourier-based coherence methods, such as periodogram, maximum entropy and multitaper methods, have reported that the recovered T e is usually overestimated when mirroring is performed [e.g., Lowry and Smith, 1994;Ojeda and Whitman, 2002;Stephen et al, 2003]. The mirroring introduces artificial long-wavelength signals into the data, which have the effect of shifting the coherence transition to smaller wave numbers [Lowry and Smith, 1994;McKenzie and Fairhead, 1997;Ojeda and Whitman, 2002].…”

Section: Effect Of Mirroringmentioning

confidence: 99%

“…[36] The preprocessing technique of mirroring the gravity/topography data before performing a Fourier transform has been performed in many studies [e.g., Zuber et al, 1989;Lowry and Smith, 1994;Macario et al, 1995;Hartley et al, 1996;McKenzie and Fairhead, 1997;Poudjom Djomani et al, 1999;Ojeda and Whitman, 2002;Stephen et al, 2003;Stark et al, 2003]. Authors using mirroring with Fourier-based coherence methods, such as periodogram, maximum entropy and multitaper methods, have reported that the recovered T e is usually overestimated when mirroring is performed [e.g., Lowry and Smith, 1994;Ojeda and Whitman, 2002;Stephen et al, 2003].…”

Section: Effect Of Mirroringmentioning

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

“…Using two different window sizes, we ensured that window size does not affect the Te values to any considerable extent. For example, Stephen and Singh (2003) used MTM spectral analysis for estimating Te in the south Indian shield. They used window sizes of 450×450 km 2 , 620×620 km 2 and 750×750 km 2 .…”

Section: Resultsmentioning

confidence: 99%

Elastic thickness estimates at northeast passive margin of North America and its implications

et al. 2011

View full text Add to dashboard Cite

Global estimates of the elastic thickness (Te) of the structure of passive continental margins show wide and varying results owing to the use of different methodologies. Earlier estimates of the elastic thickness of the North Atlantic passive continental margins that used flexural modelling yielded a Te value of ∼20-100 km. Here, we compare these estimates with the Te value obtained using orthonormalized Hermite multitaper recovered isostatic coherence functions. We discuss how Te is correlated with heat flow distribution and depth of necking. The E-W segment in the southern study region comprising Nova Scotia and the Southern Grand Banks show low Te values, while the zones comprising the NE-SW zones, viz., Western Greenland, Labrador, Orphan Basin and the Northern Grand Bank show comparatively high Te values. As expected, Te broadly reflects the depth of the 200-400 • C isotherm below the weak surface sediment layer at the time of loading, and at the margins most of the loading occurred during rifting. We infer that these low Te measurements indicate Te frozen into the lithosphere. This could be due to the passive nature of the margin when the loads were emplaced during the continental break-up process at high temperature gradients.

show abstract

Elastic thickness and isostatic coherence anisotropy in the South Indian Peninsular Shield and its implications

Cited by 21 publications

References 16 publications

On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis

On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis

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

Elastic thickness estimates at northeast passive margin of North America and its implications

Contact Info

Product

Resources

About