Shear wave dispersion and attenuation in fine‐grained synthetic olivine aggregates: Preliminary results

Tan, Ben H.; Jackson, Ian; Gerald, John Fitz

doi:10.1029/97gl00860

Cited by 61 publications

(17 citation statements)

References 19 publications

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“…Broadly similar absorption band behavior has been described in previous studies of olivine‐dominated materials. Values of the power law exponent α in the frequency dependence of Q −1 ranging from 0.17 to 0.35 have been inferred from studies of natural olivine‐rich rocks, derivative materials and synthetic forsterite single crystals [ Berckhemer et al , 1982; Gueguen et al , 1989; Jackson et al , 1992; Tan et al , 1997, 2001; Gribb and Cooper , 1998]. Broadly comparable values for the activation energy (350–510 kJ mol −1 ) have been reported for the dissipation measured on single‐crystal forsterite [ Gueguen et al , 1989] and the purest of the hot‐pressed olivine polycrystals [ Tan et al , 1997, 2001], and for steady state diffusional creep of Fo 90 aggregates tested in conventional large‐strain compressive tests [ Hirth and Kohlstedt , 1995].…”

Section: Discussionmentioning

confidence: 99%

“…However, detailed interpretation of the observed behavior was significantly complicated by the occurrence of thermal microcracking, by the progressive dehydration of hydrous layer‐silicate minerals, and, in the study of Berckhemer et al, by melting. More recently, the difficulties arising from the chemical complexity of natural rocks and the inevitable microcracking during thermal cycling of relatively coarse‐grained materials have been circumvented through promising exploratory studies of fine‐grained synthetic materials [ Tan et al , 1997; Gribb and Cooper , 1998; Tan et al , 2001]. Viscosities inferred from the torsional microcreep tests of these studies are similar to those associated with grain‐size‐sensitive behavior at the much larger strains of conventional deformation experiments.…”

Section: Introductionmentioning

confidence: 99%

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Grain‐size‐sensitive seismic wave attenuation in polycrystalline olivine

et al. 2002

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[1] In order to investigate the processes responsible for the attenuation of seismic shear waves in the Earth's upper mantle, four olivine polycrystals ranging in mean grain size d from 3 to 23 mm have been fabricated, characterized, and mechanically tested in torsion at high temperatures and seismic frequencies. Both the shear modulus, which governs the shear wave speed V S , and the dissipation of shear strain energy Q À1 have been measured as functions of oscillation period T o , temperature T, and, for the first time, grain size. At sufficiently high T all four specimens display similar absorption band viscoelastic behavior, adequately represented for 1000 < T < 1200 or 1300°C and 1 < T o < 100 s, by the expression] a with A = 7.5 Â 10 2 s Àa mm a , a = 0.26 and E = 424 kJ mol À1 . This mildly grain-size-sensitive viscoelastic behavior of melt-free polycrystalline olivine is attributed to a combination of elastically and diffusionally accommodated grain boundary sliding, the latter becoming progressively more important with increasing T and/or T o . Extrapolation to the larger (mm-cm) grain sizes expected in the Earth's upper mantle yields levels of dissipation comparable with those observed seismologically, implying that the same grain-size-sensitive processes might be responsible for much of the observed seismic wave attenuation. The temperature sensitivity of V S is increased substantially by the viscoelastic relaxation allowing the lateral variability of wave speeds to be associated with relatively small temperature perturbations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Grain‐size‐sensitive seismic wave attenuation in polycrystalline olivine

et al. 2002

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“…An increase of the temperature in the upper mantle could also decrease the shear wave velocity, as suggested by laboratory measurements of the shear modulus (e.g. Tan et al 1997;Jackson et al 2002) and that could contribute to the presence of a LVZ. From the strength of the signal we observed beneath La Réunion, we propose that the detected LVZ likely results from both high temperature and partial melt or magma locally stored at those depths.…”

Section: Hotspot-related Lvz Beneath La Réunionmentioning

confidence: 99%

Crustal and uppermost mantle structure variation beneath La Réunion hotspot track

Fontaine¹,

Barruol²,

Tkalčić

et al. 2015

Geophys. J. Int.

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“…For instance, we would expect the effect of increased temperature to be such that both bulk-sound speed and shear wave speed would decrease, with slightly greater change in shear wave speed. At elevated temperature, changes in shear modulus may be rather larger than for bulk modulus; recent laboratory experiments show strong change in shear modulus as the solidus is approached [Tan et al, 1997].…”

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confidence: 99%

Joint seismic tomography for bulk sound and shear wave speed in the Earth's mantle

Kennett¹,

Widiyantoro²,

Hilst³

1998

J. Geophys. Res.

224

152

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Abstract. High-quality P and S travel times are now available from careful reprocessing of data reported to international agencies. A restricted data set has been extracted,for which comparable ray coverage is achieved for P and S, and used for a joint inversion to produce a three-dimensional model for shear and bulk sound velocities represented in terms of 2 ø x 2 ø cells and 18 layers in depth through the mantle. About 106 times for each of P and S are combined to produce 312,549 summary rays for each wave type. Linearizing about the ak135 reference model, 583,200 coupled tomographic equations are solved using an iterative partitioned scheme. Clear high-resolution images are obtained for both bulk-sound speed and shear wavespeed. The bulk and shear moduli have differing sensitivity to temperature and mineral composition, and so the images of the two velocity distributions help to constrain the nature of the processes which produce the variations. Different heterogeneity regimes can be recognised in the upper mantle, the transition zone, most of the lower mantle, and the lowermost mantle. In the upper mantle, many features can be explained by thermal effects; but in some orogenic zones (e.g. western North America), the opposite sense of the bulk-sound and shear wave speed variation requires compositional effects or volatiles to outweigh any thermal effects. In the lower mantle, pronounced narrow structures which may represent remnant subduction are most marked in shear. The level of large-scale variations in bulk sound speed compared to shear diminishes with depth in the lower mantle reaching a minimum near 2000 km. Below this depth, the variability of both wave speeds increases. Near the core-mantle boundary the variations of the two wave speeds show little concordance, suggesting the presence of widespread chemical heterogeneity.

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Shear wave dispersion and attenuation in fine‐grained synthetic olivine aggregates: Preliminary results

Cited by 61 publications

References 19 publications

Grain‐size‐sensitive seismic wave attenuation in polycrystalline olivine

Grain‐size‐sensitive seismic wave attenuation in polycrystalline olivine

Crustal and uppermost mantle structure variation beneath La Réunion hotspot track

Joint seismic tomography for bulk sound and shear wave speed in the Earth's mantle

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