Seismic wave propagation in fully anisotropic axisymmetric media

Driel, Martin van; Nissen‐Meyer, Tarje

doi:10.1093/gji/ggu269

Cited by 23 publications

(5 citation statements)

References 57 publications

(71 reference statements)

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“…To simulate IC anisotropy with a fast axis parallel to ERA, we use ak135 (Kennett et al., 1995) as a background model and compare it to ak135 with an increased IC

{v}_{p}

of 3.2% along the polar direction (Van Driel & Nissen‐Meyer, 2014), which is a similar strength of IC anisotropy inferred by pioneering studies (e.g., Morelli et al., 1986; Tromp, 1993). The negative peak in the amplitude (white fringe) at 2,405 s on the correlogram (Figure 3a) followed by a positive peak in the amplitude (black fringe) corresponds to the energy arrival of I2*.…”

Section: New Methods Developmentmentioning

confidence: 95%

A New Probe Into the Innermost Inner Core Anisotropy via the Global Coda‐Correlation Wavefield

2022

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Introduction and Motivation Inner Core AnisotropyThe Earth's inner core (IC) is a solid ball with a radius of about 1,220 km (e.g., Kennett et al., 1995) located in the center of our planet. As the Earth cools, the IC grows over time through solidification of the liquid outer core (Buffett et al., 1992;Jacobs, 1953). The release of latent heat and light elements during solidification drives convection in the outer core, providing energy for the geodynamo and generating Earth's magnetic field (e.g., Gubbins et al., 2003;Labrosse & Macouin, 2003;Loper, 1984). In addition to the decay of radioactive isotopes and the Earth's long-term secular cooling, the heat loss from the Earth's core is one of the largest energy sources driving the mantle convection-the primary mechanism responsible for plate tectonics. Therefore, studies on the IC have the potential to unravel the history of the internal dynamic processes of our planet. Unfortunately, progress on seismic imaging of the Earth's IC is limited by the poor worldwide distribution of large sources and

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“…To simulate IC anisotropy with a fast axis parallel to ERA, we use ak135 (Kennett et al., 1995) as a background model and compare it to ak135 with an increased IC

{v}_{p}

Section: New Methods Developmentmentioning

confidence: 95%

A New Probe Into the Innermost Inner Core Anisotropy via the Global Coda‐Correlation Wavefield

2022

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“…Apart from a compromise on model symmetry, the solver does not make any limiting assumptions regarding short-period wave propagation physics (the lack of rotation and gravity is not relevant for periods below 100 s) or on the source radiation pattern. Transverse anisotropy -the most complex type of anisotropy for a spherically symmetric model [61] -and attenuation [62] can also be accounted for.…”

Section: Axisem: 25-d Global Wavefieldsmentioning

confidence: 99%

High-frequency global wavefields for local 3D structures by wavefield injection and extrapolation

Pienkowska¹,

Monteiller²,

Nissen‐Meyer³

2024

Preprint

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Earth structure is multiscale, and seismology remains the primary means of deciphering signatures from small structures over large distances. To enable this at the highest resolution, we present a flexible injection and extrapolation type hybrid framework that couples wavefields from a precomputed global database of accurate Green's functions with a local three dimensional (3-D) method of choice (e.g. a spectral element of a finite difference solver). The interface allows to embed a full 3-D domain in a spherically symmetric Earth model, tackling large-scale wave propagation with focus on localized heterogeneous complex structures. Thanks to reasonable computational costs (10k CPU hours) and storage requirements (a few TB for 1 Hz waveforms) of databases of global Green's functions, the method provides coupling of 3-D wavefields that can reach the highest observable body-wave frequencies in the 1-4 Hz range. The framework is highly flexible and adaptable; alterations in source properties (radiation patterns, source-time function), in the source-receiver geometry, and in local domain dimensions and location can be introduced without re-running the global simulation. The once-and-for-all database approach reduces the overall computational cost by a factor of 5,000-100,000 relative to a full 3-D run, provided that the local domain is of the order of tens of wavelengths in size. In this paper we present the details of the method and its implementation, show benchmarks with a 3-D spectral-element solver, discuss its setup-dependent performance, and explore possible wave-propagation applications.

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“…To this end, the spectral-element solver AxiSEM was used (Nissen-Meyer et al, 2014). It separates the problem of wave propagation in a cylindrically or spherically symmetric object into an analytical solution of the problem in the azimuthal (ϕ) direction perpendicular to the source-receiver plane, and a numerical spectral-element discretisation within the in-plane r, θ, which reduces the numerical cost to that of a 2D method (Nissen-Meyer et al, 2008 and includes attenuation (van Driel and Nissen-Meyer, 2014a) and anisotropy (van Driel and Nissen-Meyer, 2014b). The software was modified to handle general 1D velocity profiles.…”

Section: Wavefield Modelingmentioning

confidence: 99%

Seismic Wave Propagation in Icy Ocean Worlds

et al. 2018

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Seismology was developed on Earth and shaped our model of the Earth's interior over the twentieth century. With the exception of the Philae lander, all in situ extraterrestrial seismological effort to date was limited to other terrestrial planets. All have in common a rigid crust above a solid mantle. The coming years may see the installation of seismometers on Europa, Titan, and Enceladus, so it is necessary to adapt seismological concepts to the setting of worlds with global oceans covered in ice. Here we use waveform analyses to identify and classify wave types, developing a lexicon for icy ocean world seismology intended to be useful to both seismologists and planetary scientists. We use results from spectral‐element simulations of broadband seismic wavefields to adapt seismological concepts to icy ocean worlds. We present a concise naming scheme for seismic waves and an overview of the features of the seismic wavefield on Europa, Titan, Ganymede, and Enceladus. In close connection with geophysical interior models, we analyze simulated seismic measurements of Europa and Titan that might be used to constrain geochemical parameters governing the habitability of a sub‐ice ocean.

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Seismic wave propagation in fully anisotropic axisymmetric media

Cited by 23 publications

References 57 publications

A New Probe Into the Innermost Inner Core Anisotropy via the Global Coda‐Correlation Wavefield

A New Probe Into the Innermost Inner Core Anisotropy via the Global Coda‐Correlation Wavefield

High-frequency global wavefields for local 3D structures by wavefield injection and extrapolation

Seismic Wave Propagation in Icy Ocean Worlds

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