Shear wave attenuation and dispersion in melt‐bearing olivine polycrystals: 1. Specimen fabrication and mechanical testing

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

doi:10.1029/2003jb002406

Cited by 137 publications

(234 citation statements)

References 27 publications

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“…Gribb & Cooper 1998;Jackson et al 2004;Sundberg & Cooper 2010). According to these experiments, within the seismic frequency range, the mechanical loss L (inverse of the quality factor Q) varies with angular frequency u according to a power law: L ∝ u −a with 0.2 < a < 0.35.…”

Section: Introductionmentioning

confidence: 96%

Stress concentrations, diffusionally accommodated grain boundary sliding and the viscoelasticity of polycrystals

2010

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Using analytical and numerical methods, we analyse the Raj-Ashby bicrystal model of diffusionally accommodated grain-boundary sliding for finite interface slopes. Two perfectly elastic layers of finite thickness are separated by a given fixed spatially periodic interface. Dissipation occurs by time-periodic shearing of the viscous interfacial region, and by time-periodic grain-boundary diffusion. Although two time scales govern these processes, of particular interest is the characteristic time t D for grain-boundary diffusion to occur over distances of order of the grain size. For seismic frequencies ut D 1, we find that the spectrum of mechanical loss Q -1 is controlled by the local stress field near corners. For a simple piecewise linear interface having identical corners, this localization leads to a simple asymptotic form for the loss spectrum: for ut D 1, Q −1 ∼ const.u −a . The positive exponent a is determined by the structure of the stress field near the corners, but depends both on the angle subtended by the corner and on the orientation of the interface; the value of a for a sawtooth interface having 120• angles differs from that for a truncated sawtooth interface whose corners subtend the same 120• angle. When corners on an interface are not all identical, the behaviour is even more complex. Our analysis suggests that the loss spectrum of a finely grained solid results from volume averaging of the dissipation occurring in the neighbourhood of a randomly oriented three-dimensional network of grain boundaries and edges.

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Section: Introductionmentioning

confidence: 96%

Stress concentrations, diffusionally accommodated grain boundary sliding and the viscoelasticity of polycrystals

2010

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“…Anelastic attenuation varies exponentially with temperature and thus has a stronger sensitivity to temperature variations than elastic velocities [Karato and Spetzler, 1990;Jackson et al, 2002]. Studies indicate attenuation is also sensitive to the presence of volatiles and melt [Karato, 2003;Jackson et al, 2004]. An understanding of attenuation structure and anelasticity can provide additional insight into the dynamics and composition of the Earth.…”

Section: Introductionmentioning

confidence: 99%

Upper mantle Q structure beneath old seafloor in the western Pacific

2014

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The Pacific Lithosphere Anisotropy and Thickness Experiment ocean bottom seismometer array south of the Shatsky Rise allows imaging the attenuation structure of the upper mantle in the oldest parts of the Pacific Ocean. The array consisted of eight seismometers with a lateral extent of 200 km by 600 km. Intermediate-and deep-focus earthquake sources in the Mariana and Izu-Bonin subduction zones provide paths that probe different depths beneath the seafloor. Acceleration spectra from the vertical component of P waves are inverted for the attenuation operator and corner frequency. P n propagation indicates very high Q p values in the lithosphere, of order 1000, while path-average Q p values in the upper mantle are on the order of 400. The variety of source epicentral distances and depths enables us to deduce the vertical Q p À1 structure of the upper mantle. Using the amplitude spectra directly in a weighted least squares problem that accounts for the effects of triplications in the traveltime curves, we invert for Q p À1 as a function of depth. We demonstrate that Q p is frequency dependent and adopt a power law dependence with coefficient α = 0.27. We resolve three distinct layers using a reference frequency of 1 Hz with Q p on the order of 145 at depths 100-250 km, Q p on the order of 350 at depths 250-410 km, and very high Q p with attenuation indistinguishable from zero for depths below 410 km. The P waves have a component of scattering, and thus, Q p À1 represents the maximum intrinsic attenuation beneath normal undisturbed oceanic lithosphere.

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“…In order to reflect the complexity of planetary materials, some researchers replace the single relaxation time t in the simple Burgers model with a suitably broad distribution D(t) of relaxation times to more accurately describe the response in both the time and frequency domains (Tan et al 2001;Jackson et al 2004). The components of the complex compliance of this "extended" Burgers model are given by: 7.16) where the parameter D is anelastic relaxation strength, which is a direct function of the concentration, mobility and geometry of the defect(s) accommodating the relaxation (Jackson et al 2002).…”

Section: Extended Burgers Modelmentioning

confidence: 99%