Origin of lateral variation of seismic wave velocities and density in the deep mantle

Karato, S.; Karki, Bijaya B.

doi:10.1029/2001jb000214

Cited by 282 publications

(334 citation statements)

References 72 publications

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“…At and beyond transition zone depths, the amplitude of density anomalies are likely to be at least as large as that of shear sound speed variations [Resovsky and Trampert, 2003]. Existing mineral physics data show that this is not compatible with a purely thermal origin [e.g., Karato and Karki, 2001].…”

Section: Long-wavelength Anticorrelations Of Wave Speeds and Densitymentioning

confidence: 99%

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Towards a quantitative interpretation of global seismic tomography

Trampert

Hilst

2005

Geophysical Monograph Series

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We review the success of seismic tomography in delineating spatial variations in the propagation speed of seismic waves on length scales from several hundreds to many thousands of kilometers. In most interpretations these wave speed variations are thought to reflect variations in temperature. Careful consideration of shear wave, bulk sound, and, most recently, density variations is, however, producing increasingly compelling evidence for chemical heterogeneity (that is, spatial variations in bulk major element composition) having a first-order effect on the lateral variations in mass density and elasticity of the mantle. This has profound consequences for our understanding of mantle dynamics and the thermochemical evolution of our planet. We argue that the quantitative integration of constraints from seismology, mineral physics, and geodynamics, which underlies the inference of thermochemical parameters, requires careful uncertainty analyses and should move away from emphasizing visually pleasing images and single, nonunique solutions.

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Section: Long-wavelength Anticorrelations Of Wave Speeds and Densitymentioning

confidence: 99%

“…In combination with mineral physics data, the seismologically measured ratio is thought to indicate whether thermal and/or chemical causes are responsible for the observed lateral variations in wave speeds [Karato and Karki, 2001]. However, there are several caveats that one should be aware of.…”

Section: Radial and Lateral Variation Of R=d1nv S /D1nv Pmentioning

confidence: 99%

Towards a quantitative interpretation of global seismic tomography

Trampert

Hilst

2005

Geophysical Monograph Series

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“…These values seem to fall into the uncertainties of seismic observations and geodynamic modeling (e.g., R S/P $ 1.6, R f/S $ 0.3 in the transition zone [Masters et al, 2000;Karato and Karki, 2001]). …”

Section: Geophysical Implicationsmentioning

confidence: 99%

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Tsuchiya

2009

J. Geophys. Res.

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Protons are found to bond to the O1 site to align the OH dipoles along the edges of M3 vacancies. Calculated elastic constants, bulk and shear moduli, are found to decrease almost linearly with increasing water content but to increase linearly with increasing pressure. At 15 GPa and static 0 K condition, incorporation of 3.3 wt % H 2 O into wadsleyite, which corresponds to the maximum solubility of hydrous wadsleyite, reduces V P and V S by about 3.9 and 4.8%, respectively. This indicates that 1 wt % H 2 O hydration of wadsleyite corresponds to the temperature effects on bulk and shear moduli about 430 K (0 GPa) to 340 K (20 GPa) and 350 K (0 GPa) to 290 K (20 GPa), respectively. The transversely isotropic aggregates demonstrate largest positive polarization anisotropy V SH À V SV when the c axis aligns vertically in both dry and wet cases.Citation: Tsuchiya, J., and T. Tsuchiya (2009), First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure,

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“…Logarithmic derivatives ∂ ln ξ/∂X, where ξ is V P , V S , V Φ , or ρ and X the phase fraction corresponding to changes in the physical properties associated with chemical variations, are helpful to consider possible sources of a chemical origin to explain the velocity and density heterogeneity in the LM [Karato and Karki, 2001;Tsuchiya and Tsuchiya, 2006]. These values estimated for chemical variations are listed in Table S4 together with those obtained in previous studies at static conditions on the effects of variations in CaSiO 3 , Al 2 O 3 , and FeSiO 3 components.…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

Small shear modulus of cubic CaSiO₃ perovskite

Kawai

Tsuchiya

2015

Geophysical Research Letters

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Ca‐perovskite (CaPv) is considered to be one of the most abundant minerals in the Earth's lower mantle (LM). Furthermore, previous static calculations and mean‐field theory suggest that it has a much larger shear modulus than bridgmanite (MgPv). In this study, the elasticity of cubic CaPv was reinvestigated using the density functional constant‐temperature first principles molecular dynamics method under the correct conditions to simulate its elasticity. Our new results clearly demonstrate that cubic CaPv has comparable bulk and slightly smaller shear moduli than Fe‐bearing MgPv. This is because the boundary condition for the supercell used in this study allows for the rotational phonon motion of SiO6 octahedra under strain, which predominantly affects the decrease in C11 and C44. Acoustic wave velocities determined from the elastic moduli indicate that cubic CaPv has slower velocities and larger densities than Fe‐bearing MgPv and preliminary reference Earth model in the LM. This suggests that if CaPv‐rich material exists, it can accumulate in the lowermost LM and produce a seismically low‐velocity anomaly.

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Origin of lateral variation of seismic wave velocities and density in the deep mantle

Cited by 282 publications

References 72 publications

Towards a quantitative interpretation of global seismic tomography

Towards a quantitative interpretation of global seismic tomography

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Small shear modulus of cubic CaSiO₃ perovskite

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Origin of lateral variation of seismic wave velocities and density in the deep mantle

Cited by 282 publications

References 72 publications

Towards a quantitative interpretation of global seismic tomography

Towards a quantitative interpretation of global seismic tomography

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Small shear modulus of cubic CaSiO3 perovskite

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Product

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Small shear modulus of cubic CaSiO₃ perovskite