Aspherical Earth structure from fundamental spheroidal-mode data

Masters, G.; Jordan, Thomas H.; Silver, Paul G.; Gilbert, Freeman

doi:10.1038/298609a0

Cited by 295 publications

(162 citation statements)

References 17 publications

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“…Figure 1 shows the degree 2 component of the inversion result for both the elastic and anelastic heterogeneity. The high-frequency anomalies (equivalent to high-velocity anomalies) are located in the western Pacific and central Atlantic, which are consistent with previous studies (e.g., Masters et al, 1982) and the high-attenuation anomalies are located in the central Pacific and southern Africa. The high-attenuation anomalies located presumably in the transition zone correlate with regions of slow P-wave velocity in the lower mantle (e.g., Inoue et al, 1990) and with hotspots.…”

Section: Introductionsupporting

confidence: 81%

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Recent Seismological Studies on Upper Mantle Structure.

Suetsugu

1995

J,Phys,Earth

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Our understanding of three-dimensional upper mantle structure has been greatly advanced in the last decade. We review recent seismological studies on upper mantle structure conducted in Japanese universities and institutes. Studies reviewed in the present paper involve global and regional mantle heterogeneity, large-scale seismic anisotropy derived from surface wave dispersion, topography of the 410-km and the 660-km discontinuities, and the fate of deep slabs.

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Section: Introductionsupporting

confidence: 81%

“…There are widely distributed slow anomalies from the Indian Ocean to the arctic area. The transition zone also shows a degree 2 pattern (e.g., Masters et al, 1982): fast anomalies at South America and its antipode in the western Pacific and slow anomalies at the south Pacific and its antipode. In the depth range 1,200-1,400 km ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Recent Seismological Studies on Upper Mantle Structure.

Suetsugu

1995

J,Phys,Earth

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“…In the transition zone, our results show some differences but the major trends remain: in particular the large region of fast mantle in the South-Atlantic. That region is also fast in the even order expansion of Masters et al ( 1982). The differences between our maps and those of Woodhouse and Dziewonski ( 1983) can be attributed to their neglect of lateral variations in anisotropy and their simplified treatment of the crust.…”

Section: Discussionmentioning

confidence: 34%

Anisotropy and shear‐velocity heterogeneities in the upper mantle

Nataf¹,

Nakanishi²,

Anderson³

1984

Geophysical Research Letters

199

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Abstract. Long-period surface waves are used to map lateral heterogeneities of velocity and anisotropy in the upper mantle. The dispersion curves are expanded in spherical harmonics up to degree 6 and inverted to find the depth structure. The data are corrected for the effect of surface layers and both Love and Rayleigh waves are used. Shear wave velocity and shear polarization anisotropy can be resolved down to a depth of about 450 km. The shear wave velocity distribution to 200 km depth correlates with surface tectonics, except in a few anomalous regions. Below that depth the correlation vanishes. Cold subducted material shows up weakly at 350 km as fast S-wave anomalies. In the transition region a large scale pattern appears with fast mantle in the South-Atlantic. S-anisotropy at 200 km can resolve uprising or downwelling currents under some ridges and subduction zones. The Pacific shows a NW-SE fabric.

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“…The longer wavelength part of the geoid, £ = 2-3, correlates with velocities in the deeper part of the mantle, i.e. lower mantle [Dziewonski et al, 1977;Hager, personal communication] and transition region [Masters et al, 1982;Woodhouse and Dziewonski, 1983]. Fig.…”

Section: Introductionmentioning

confidence: 99%

“…However, we still have a poor understanding of the scale of mantle convection and the driving mechanism of plate tectonics. Three-dimensional global maps of seismic velocity anomalies are starting to become available Masters et a!., 1982] and promise to help constrain the nature of the flow. Seismic techniques can be used to map anisotropy as well as heterogeneity and, in principle, can determine crystal orientation.…”

Section: Introductionmentioning

confidence: 99%

Mapping convection in the mantle

Tanimoto¹,

Anderson²

1984

Geophysical Research Letters

185

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Abstract. Long-period (100-250 sec.) Love and Rayleigh waves are used to map heterogeneity and azimuthal anisotropy in the upper mantle. Spherical harmonic descriptions of anisotropy up to £ = m = 3 and 28 are derived. Azimuthal anisotropy obtains values as high as 1 Yz OJo. There is good correlation of fast Rayleigh wave directions with upper mantle return flow directions derived from kinematic considerations. This is consistent with the a-axis of olivine being aligned in the flow direction. The main differences between the flow models and the Rayleigh wave azimuthal variation maps occur in the vicinity of hotspots. Hawaii, for example, appears to perturb the return flow. There is strong correlation of the geoid and surface wave velocity at £ = 4 and 5. Slow regions at this scale are associated with geoid highs and high heat flow, consistent with upwelling convective flow or with isostatically compensated regions of low density. The correlation of azimuthal anisotropy with upper mantle return flow directions, rather than with plate directions, suggests that part of the return flow is in the upper mantle and this, in turn, implies a low viscosity channel.

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Aspherical Earth structure from fundamental spheroidal-mode data

Cited by 295 publications

References 17 publications

Recent Seismological Studies on Upper Mantle Structure.

Recent Seismological Studies on Upper Mantle Structure.

Anisotropy and shear‐velocity heterogeneities in the upper mantle

Mapping convection in the mantle

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