Azimuthal anisotropy in the upper mantle from observations of<i>P</i>-to-<i>S</i>converted phases: application to southeast Australia

Girardin, N.; Farra, Véronique

doi:10.1046/j.1365-246x.1998.00525.x

Cited by 102 publications

(71 citation statements)

References 19 publications

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“…Converted phases (e.g., Kosarev et al 1984;Girardin and Farra 1998;Iidaka and Niu 1998) or phases that have undergone an underside surface reflection (e.g., SS; Wolfe and Silver 1998, or sS;Anglin and Fouch 2005) can be useful for upper mantle anisotropy studies, although, again, some caution must be exercised. Converted phases may have low signal-to-noise ratio that makes accurate splitting measurements difficult; this can be improved by stacking, but then information about complex anisotropy may be lost.…”

Section: Array Datamentioning

confidence: 99%

“…Another type of phase that holds promise for shear wave splitting practitioners is converted phases (e.g., Girardin and Farra 1998;Vinnik et al 2002), including those converted at seismic discontinuities such as the Moho, or the 410 and 660 km transition zone discontinuities. Converted phases are already used to detect sharp changes in anisotropic structure by looking for backazimuthal variations in transverse component receiver functions that are the manifestations of so-called P-to-SH conversions at shallow (crust or uppermost mantle) depths beneath a station (e.g., Levin and Park 1998;Park et al 2004).…”

Section: The Use Of Reflected and Converted Phasesmentioning

confidence: 99%

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Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth's mantle yield constraints on the strength and geometry of elastic anisotropy in various regions, including the upper mantle, the transition zone, and the D 00 layer. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. While shear wave splitting is an unambiguous indicator of anisotropy, the fact that it is typically a near-vertical path-integrated measurement means that splitting measurements generally lack depth resolution. Because shear wave splitting yields some of the most direct constraints we have on mantle flow, however, understanding how to make and interpret splitting measurements correctly and how to relate them properly to mantle flow is of paramount importance to the study of mantle dynamics. In this paper, we review the state of the art and recent developments in the measurement and interpretation of shear wave splitting-including new measurement methodologies and forward and inverse modeling techniques,-provide an overview of data sets from different tectonic settings, show how they help us relate mantle flow to surface tectonics, and discuss new directions that should help to advance the shear wave splitting field.

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Section: Array Datamentioning

confidence: 99%

Section: The Use Of Reflected and Converted Phasesmentioning

confidence: 99%

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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“…[50] Both body wave [Clitheroe and van der Hilst, 1998;Girardin and Farra, 1998;Ö zalaybey and Chen, 1999] and surface wave [Debayle and Kennett, 2000; studies suggest that the seismic anisotropy of the Australian lithosphere is more complex than either endmember model, vertically coherent deformation [Silver and Chan, 1988] or present-day mantle deformation [Vinnik et al, 1995] would predict. Measurements of the birefringence of SKS phases in Australia by Clitheroe and van der Hilst [1998] and Ö zalaybey and Chen [1999] are at odds with each other.…”

Section: Mechanical Anisotropy and Lithospheric Strainmentioning

confidence: 99%

Spatiospectral localization of isostatic coherence anisotropy in Australia and its relation to seismic anisotropy: Implications for lithospheric deformation

2003

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[1] We investigate the two-dimensional (2-D) nature of the coherence between Bouguer gravity anomalies and topography on the Australian continent. The coherence function or isostatic response is commonly assumed to be isotropic. However, the fossilized strain field recorded by gravity anomalies and their relation to topography is manifest in a degree of isostatic compensation or coherence which does depend on direction. We have developed a method that enables a robust and unbiased estimation of spatially, directionally, and wavelength-dependent coherence functions between two 2-D fields in a computationally efficient way. Our new multispectrogram method uses orthonormalized Hermite functions as data tapers, which are optimal for spectral localization of nonstationary, spatially dependent processes, and do not require solving an eigenvalue problem. We discuss the properties and advantages of this method with respect to other techniques. We identify regions on the continent marked by preferential directions of isostatic compensation in two wavelength regimes. With few exceptions, the short-wavelength coherence anisotropy is nearly perpendicular to the major trends of the suture zones between stable continental domains, supporting the geological observation that such zones are mechanically weak. Mechanical anisotropy reflects lithospheric strain accumulation, and its presence must be related to the deformational processes affecting the lithosphere integrated over time. Threedimensional models of seismic anisotropy obtained from surface wave inversions provide an independent estimate of the lithospheric fossil strain field, and simple models have been proposed to relate seismic anisotropy to continental deformation. We compare our measurements of mechanical anisotropy with our own model of the azimuthally anisotropic seismic wave speed structure of the Australian lithosphere. The correlation of isostatic anisotropy with directions of fast wave propagation gleaned from the azimuthal anisotropy of surface waves decays with depth. This may support claims that above $200 km, internally coherent deformation of the entire lithosphere is responsible for the anisotropy present in surface wave speeds or split shear waves.

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“…Seismic refraction studies on continents have revealed a wealth of possible 'stretch marks' in the lithosphere at depths <100 km, and initial Ps receiver functions of the transverse component suggest that many 'interfaces' resemble thin shear zones with a discernible rock texture (Bostock, 1998;Byrne et al, 1997;Calvert et al, 1995;Girardin and Farra, 1998;Hajnal et al, 1997;Levin and Park, 1997b;Levin and Park, 2000;Mercier et al, 2008;Sherrington et al, 2004;Warner et al, 1996;Wilson et al, 2004). The S-to-P conversions identified in S receiver functions (Farra and Vinnik, 2000) have been associated with anisotropic shear zones in the uppermost mantle (Wittlinger et al, 2004).…”

Section: Converted Waves and Lithospheric Anisotropymentioning

confidence: 99%

Theory and Observations - Seismic Anisotropy

Maupin

Park

2015

Treatise on Geophysics

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Azimuthal anisotropy in the upper mantle from observations ofP-to-Sconverted phases: application to southeast Australia

Cited by 102 publications

References 19 publications

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Spatiospectral localization of isostatic coherence anisotropy in Australia and its relation to seismic anisotropy: Implications for lithospheric deformation

Theory and Observations - Seismic Anisotropy

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