Research ArticleGEOPHYSICS

Seismically determined elastic parameters for Earth’s outer core

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Science Advances  27 Jun 2018:
Vol. 4, no. 6, eaar2538
DOI: 10.1126/sciadv.aar2538
  • Fig. 1 Vinet EoS parameter posterior distributions and trade-offs.

    ρ0 is presented using the fixed molar mass of 0.05 kg and inverted molar volume. The black stars show the median values used for the EPOC-Vinet model in Fig. 2. Numbers on the lower left panels indicate correlation coefficients between the parameters in question.

  • Fig. 2 The EPOC-Vinet velocity and density models.

    P wave or bulk sound velocities (left) and densities (right) for EPOC-Vinet (green) compared to PREM (orange lines). The models produced by the median parameters are shown as the dark green lines, the shaded region encompasses two-thirds of the values, and the dashed lines encompass 95% of the values at each depth.

  • Fig. 3 SmKS differential travel time predictions.

    Predictions made for EPOC-Vinet, PREM, ak135, iasp91, and SP6 (60) are compared to body wave array-based observations from three events and for three phase pairs from (18). The green error bars represent predictions using the velocity ranges in table S3.

  • Fig. 4 Relevant physical properties of the EPOC-Vinet and PREM models.

    Bullen parameter (top left) and squared Brunt-Väisälä frequency (bottom left) as a function of depth. Velocity as a function of density (right). Ranges for velocity and density are calculated when a velocity is predicted by at least 80% of the models. Colors are as in Fig. 2.

  • Fig. 5 Mode central frequency sensitivity kernels.

    Kernels showing sensitivity of mode central frequencies to bulk modulus (top) and density (bottom), for modes that have more than 10% of their sensitivity in the outer core (pink region) for PREM. Modes in teal were not used when PREM was constructed.

  • Table 1 Elastic parameters for the outer core for EPOC-Vinet and for a Vinet EoS fit to PREM.

    Molar mass is fixed in the inversion at 0.05 kg. The values in brackets encompass two-thirds of the parameter values.

    EPOC-VinetPREM-Vinet
    K0S (GPa)
    Reference isentropic bulk modulus
    67.5
    (61.7–73.3)
    79.7
    Embedded Image
    Pressure derivative of K0S
    6.12
    (6.02–6.23)
    5.89
    ρ0 (kg/m3)
    Reference molar density
    6110
    (6010–6210)
    6210
    V0 (m−3)
    Reference molar volume
    8.18 × 10−6
    (8.05 × 10−6–8.32 × 10−6)
    8.06 × 10−6

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/6/eaar2538/DC1

    section S1. Birch-Murnaghan EoS

    section S2. EPOC-Birch Murnaghan results

    section S3. Inversion using PREM data

    section S4. Inversion using STW105 for the rest of Earth

    section S5. Previous geophysical tests

    section S6. Body wave differential travel time predictions

    section S7. Nonlinearity of center frequencies

    section S8. Mode data set

    section S9. Model values

    fig. S1. Parameter posterior distributions and trade-offs for the three Birch Murnaghan EoS parameters.

    fig. S2. The EPOC-BM velocity and density models.

    fig. S3. Relevant physical properties of the EPOC-Vinet and PREM models.

    fig. S4. Models produced by inversion of PREM data.

    fig. S5. Models produced using STW105 for the rest of Earth.

    fig. S6. Body wave differential travel time predictions.

    fig. S7. Nonlinearity of the relationship between mode center frequency and elastic parameters of the core.

    table S1. Elastic parameters for the outer core for the Birch-Murnaghan EoS and for Birch-Murnaghan EoS fits to PREM.

    table S2. Mode center frequencies used.

    table S3. The EPOC-Vinet model and associated velocity and density ranges.

    table S4. The EPOC-BM model and associated velocity and density ranges.

    References (61, 62)

  • Supplementary Materials

    This PDF file includes:

    • section S1. Birch-Murnaghan EoS
    • section S2. EPOC-Birch Murnaghan results
    • section S3. Inversion using PREM data
    • section S4. Inversion using STW105 for the rest of Earth
    • section S5. Previous geophysical tests
    • section S6. Body wave differential travel time predictions
    • section S7. Nonlinearity of center frequencies
    • section S8. Mode data set
    • section S9. Model values
    • fig. S1. Parameter posterior distributions and trade-offs for the three Birch Murnaghan EoS parameters.
    • fig. S2. The EPOC-BM velocity and density models.
    • fig. S3. Relevant physical properties of the EPOC-Vinet and PREM models.
    • fig. S4. Models produced by inversion of PREM data.
    • fig. S5. Models produced using STW105 for the rest of Earth.
    • fig. S6. Body wave differential travel time predictions.
    • fig. S7. Nonlinearity of the relationship between mode center frequency and elastic parameters of the core.
    • table S1. Elastic parameters for the outer core for the Birch-Murnaghan EoS and for Birch-Murnaghan EoS fits to PREM.
    • table S2. Mode center frequencies used.
    • table S3. The EPOC-Vinet model and associated velocity and density ranges.
    • table S4. The EPOC-BM model and associated velocity and density ranges.
    • References (61, 62)

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