Seismic wave propagation in anisotropic ice – Part 1: Elasticity tensor and derived quantities from ice-core properties

Diez, Anja; Eisen, Olaf

doi:10.5194/tc-9-367-2015

Cited by 57 publications

(60 citation statements)

References 53 publications

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“…Hence, the velocity of the radar wave in anisotropic ice as well as the reflection coefficient can be calculated approximately. In order to calculate seismic velocities and reflection coefficients for different anisotropic ice fabrics, we presented a framework to derive the anisotropic polycrystal elasticity tensor from COF eigenvalues in Part 1 of this work (Diez and Eisen, 2015). We apply this methodology here to calculate seismic velocities from COF eigenvalues measured along the EDML ice core, retrieved at Kohnen Station, Dronning Maud Land, Antarctica (EDML: EPICA Dronning Maud Land; EPICA: European Project for Ice Coring in Antarctica).…”

Section: A Diez Et Al: Seismic Wave Propagation In Anisotropic Ice mentioning

confidence: 99%

“…We briefly summarize our approach introduced in Part 1 of this work (Diez and Eisen, 2015) to calculate seismic velocities from the COF eigenvalues. As a first step we distinguish between different fabrics based on the COF eigenvalues and calculate two opening angles, ϕ and χ.…”

Section: Calculation Of Seismic Velocities For Anisotropic Icementioning

confidence: 99%

“…2 we introduce the field site and data sets, followed by a short summary of the calculation of the polycrystal elasticity tensor from COF eigenvalues (Part 1: Diez and Eisen, 2015) in Sect. 3.…”

Section: A Diez Et Al: Seismic Wave Propagation In Anisotropic Ice mentioning

confidence: 99%

“…The elasticity tensor of the polycrystal is then calculated by integrating a measured elasticity tensor with a normal density distribution using these opening angles (Part 1: Diez and Eisen, 2015).…”

Section: Calculation Of Seismic Velocities For Anisotropic Icementioning

confidence: 99%

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Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

et al. 2015

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Abstract.We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firnice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.

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Section: A Diez Et Al: Seismic Wave Propagation In Anisotropic Ice mentioning

confidence: 99%

Section: Calculation Of Seismic Velocities For Anisotropic Icementioning

confidence: 99%

Section: A Diez Et Al: Seismic Wave Propagation In Anisotropic Ice mentioning

confidence: 99%

Section: Calculation Of Seismic Velocities For Anisotropic Icementioning

confidence: 99%

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Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

et al. 2015

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“…It is well understood that porosity, dislocation structures, the configuration of grain boundaries, and any crystallographic preferred orientation textures play an important role in the absolute value of visco-elastic dissipation (McCarthy and Castillo-Rogez, 2013;Cole et al, 1998) and elastic wave speeds (Maurel et al, 2015;Diez and Eisen, 2015;Gusmeroli et al, 2012) in ice.…”

Section: Temperature Dependence and Pre-meltmentioning

confidence: 99%

Monitoring the temperature-dependent elastic and anelastic properties in isotropic polycrystalline ice using resonant ultrasound spectroscopy

et al. 2016

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Abstract. The elastic and anelastic properties of ice are of interest in the study of the dynamics of sea ice, glaciers, and ice sheets. Resonant ultrasound spectroscopy allows quantitative estimates of these properties and aids calibration of active and passive seismic data gathered in the field. The elastic properties and anelastic quality factor Q in laboratorymanufactured polycrystalline isotropic ice cores decrease (reversibly) with increasing temperature, but compressionalwave speed and attenuation prove most sensitive to temperature, indicative of pre-melting of the ice. This method of resonant ultrasound spectroscopy can be deployed in the field, for those situations where shipping samples is difficult (e.g. remote locations), or where the properties of ice change rapidly after extraction (e.g. in the case of sea ice).

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Ice fabric in an Antarctic ice stream interpreted from seismic anisotropy

Smith

Baird

Kendall

et al. 2017

Geophysical Research Letters

125

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Here we present new measurements of an anisotropic ice fabric in a fast moving (377 ma−1) ice stream in West Antarctica. We use ∼6000 measurements of shear wave splitting observed in microseismic signals from the bed of Rutford Ice Stream, to show that in contrast to large‐scale ice flow models, which assume that ice is isotropic, the ice in Rutford Ice Stream is dominated by a previously unobserved type of partial girdle fabric. This fabric has a strong directional contrast in mechanical properties, shearing 9.1 times more easily along the ice flow direction than across flow. This observed fabric is likely to be widespread and representative of fabrics in other ice streams and large glaciers, suggesting it is essential to consider anisotropy in data‐driven models to correctly predict ice loss and future flow in these regions. We show how passive microseismic monitoring can be effectively used to provide these data.

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Seismic wave propagation in anisotropic ice – Part 1: Elasticity tensor and derived quantities from ice-core properties

Cited by 57 publications

References 53 publications

Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

Monitoring the temperature-dependent elastic and anelastic properties in isotropic polycrystalline ice using resonant ultrasound spectroscopy

Ice fabric in an Antarctic ice stream interpreted from seismic anisotropy

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