Global anisotropy in the upper mantle inferred from the regionalization of phase velocities

Montagner, Jean‐Paul; Tanimoto, Toshiro

doi:10.1029/jb095ib04p04797

Cited by 212 publications

(132 citation statements)

References 60 publications

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“…The lateral heterogeneity obtained with azimuthal anisotropy is quite similar to that without anisotropy by Suetsugu and Nakanishi (1985). Their results were in good agreement with Montagner and Tanimoto (1990) in the entire Pacific, but inconsistent with Nishimura and Forsyth (1989) who suggested a correlation with fossil seafloor spreading direction rather than the direction of the present-day plate motion. Since the work of Aki and Kaminuma (1963), it has been widely known that SH-velocity obtained from Love wave dispersion is significantly different from SV-velocity derived from Rayleigh wave dispersion.…”

Section: Introductionsupporting

confidence: 70%

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: 70%

Recent Seismological Studies on Upper Mantle Structure.

Suetsugu

1995

J,Phys,Earth

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“…The azimuthal dependence of anisotropy has been investigated at both the global and regional scale [e.g., Forsyth, 1975;Tanimoto and Anderson, 1985;Montagner and Tanimoto, 1990; Debayle ) and (c) Rayleigh wave phase-delay sensitivity kernels K b and K a (the latter expressing sensitivity to compressional wave speed perturbations da/a). Top three plots show map views at a depth of 108 km; middle three plots show vertical slices along AB across-section with 108 km depth indicated by dotted lines; bottom three plots show AB cross-path variations in sensitivity at 108 km depth.…”

Section: Radial Anisotropymentioning

confidence: 99%

Global upper‐mantle structure from finite‐frequency surface‐wave tomography

Zhou¹,

Nolet²,

Dahlen³

et al. 2006

J. Geophys. Res.

139

119

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Journal of Geophysical Research, v. 111, n. B4, p. 24 pp, 2006. http://dx.doi.org/10.1029/2005JB003677International audienceWe report global shear-wave velocity structure and radial anisotropy in the upper mantle obtained using finite-frequency surface-wave tomography, based upon complete three-dimensional Born sensitivity kernels. Because wavefront healing effects are properly taken into account, finite-frequency surface-wave tomography improves the resolution of small-scale mantle heterogeneities, especially for deep anomalies that are constrained by the longest-period surface waves. In our finite-frequency model FFSW1, the globally averaged radial anisotropy shows a transition from positive (SH > SV) to negative anisotropy (SV > SH) at about 220 km, consistent with a change in the dominant mantle circulation pattern from predominantly horizontal flow at shallow depths to vertical flow at greater depths. The radial anisotropy beneath cratons and the old Pacific plate agrees well with previous studies. However, our model exhibits a strong negative radial anisotropy at depths greater than 120 km beneath mid-ocean ridges, a feature that is not present in previous upper-mantle models. More interestingly, the depth extent of the ridge anomalies is distinctly different beneath fast- and slow-spreading centers; anomalies beneath fast-spreading centers are stronger, but the strength decreases rapidly below 250 km. In contrast, beneath slow-spreading centers such as the northern Mid-Atlantic Ridge and the Red Sea, anomalies extend down at least to the top of the transition zone. The different depth extent of the ridge anomalies suggests that the primary driving force of slow-spreading seafloor may be different from that of fast-spreading seafloor and that active upwelling beneath slow-spreading ridges may play a major role in the opening of the seafloor

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“…Raitt et al, 1969;Forsyth, 1975;Nataf et al, 1984;Tanimoto and Anderson, 1985;Shearer and Orcutt, 1986;Montagner and Tanimoto, 1990;Silver and Chan, 1991) and laboratory experiments (e.g. Carter and Avé Lallemant, 1970;Nicolas et al, 1973;Kunze and Avé Lallemant, 1981;Chopra and Paterson, 1981;Zeuch and Green, 1984;Zhang and Karato, 1995;Tommasi et al, 1999;Zhang et al, 2000;Bystricky et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Seismic properties of the upper mantle beneath Lanzarote (Canary Islands): Model predictions based on texture measurements by EBSD

et al. 2006

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We present a petrophysical analysis of upper mantle xenoliths, collected in the Quaternary alkali basalt fields (Series III and IV) from the island of Lanzarote. The samples consist of eight harzburgite and four dunite nodules, 5 to 15 cm in size, and exhibit a typical protogranular to porphyroclastic texture. An anomalous foliation resulting from strong recovery processes is observed in half of the specimens. The lattice preferred orientations (LPO) of olivine, orthopyroxene and clinopyroxene were measured using electron backscatter diffraction (EBSD). In most samples, olivine exhibits LPOs intermediate between the typical single crystal texture and the [100] fiber texture. Occasionally, the [010] fiber texture was also observed. Simultaneous occurrence of both types of fiber textures suggests the existence of more than one deformation regime, probably dominated by a simple shear component under low strain rate and moderate to high temperature. Orthopyroxene and clinopyroxene display a weaker but significant texture. The LPO data were used to calculate the seismic properties of the xenoliths at PT conditions obtained from geothermobarometry, and were compared to field geophysical data reported from the literature. The velocity of P-waves (7.9 km/s) obtained for a direction corresponding to the existing seismic transect is in good agreement with the most recent geophysical interpretation. Our results are consistent with a roughly W-E oriented fastest P-wave propagation direction in the uppermost mantle beneath the Canary Islands, and with the lithosphere structure proposed by previous authors involving a crust-mantle boundary at around 18 km in depth, overlaid by intermediate material between 11 and 18 km.

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Global anisotropy in the upper mantle inferred from the regionalization of phase velocities

Cited by 212 publications

References 60 publications

Recent Seismological Studies on Upper Mantle Structure.

Recent Seismological Studies on Upper Mantle Structure.

Global upper‐mantle structure from finite‐frequency surface‐wave tomography

Seismic properties of the upper mantle beneath Lanzarote (Canary Islands): Model predictions based on texture measurements by EBSD

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