The kinematics of S waves in acoustic orthorhombic media

Xu, Shibo; Stovas, Alexey

doi:10.1111/1365-2478.12835

Cited by 9 publications

(3 citation statements)

References 41 publications

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“…where v j are the on-axis P wave velocities, and η 1 , η 2 and η 3 are the anellipticity parameters defined in the (x,y), (x,z) and (y,z) symmetry planes, respectively. In this case, the P wave is similar to elastic ORT case, while two S wave artefacts are completely different from their counterparts in the elastic case (Xu and Stovas, 2019b).…”

Section: Figure 13mentioning

confidence: 66%

“…In this case, the stiffness coefficient matrix takes the form (Abedi et al., 2019)

\begin{matrix} left c_{jj} = & left \{\begin{matrix} v_{j}^{2}, j = 1, 2, 3 \\ 0, j = 4, 5, 6 \end{matrix} \\ left c_{j k} = & left \frac{v_{j} v_{k}}{\sqrt{1 + 2 η_{l}}}, j, k, l = 1, 2, 3; j \neq k \neq l, \end{matrix}

where

v_{j}

are the on‐axis P wave velocities, and η 1 , η 2 and η 3 are the anellipticity parameters defined in the ( x,y ), ( x,z ) and ( y,z ) symmetry planes, respectively. In this case, the P wave is similar to elastic ORT case, while two S wave artefacts are completely different from their counterparts in the elastic case (Xu and Stovas, 2019b).…”

Section: Geometrical Characteristicsmentioning

confidence: 67%

“…The enhancement factor for acoustic ORT can be seen in Figure 5. The singularity point is clearly seen at phase angles

θ = 62 . 1^{\circ}

and

ϕ = 16 . 8^{\circ}

(the position can be computed analytically, see Xu and Stovas (2019b)) for both S1 and S2 waves. The cusps are identified at

ϕ = 0

and

θ = 90^{\circ}

and

ϕ = 90^{\circ}

and

θ = 90^{\circ}

for the S1 wave.…”

Section: Geometrical Characteristicsmentioning

confidence: 99%

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Geometrical characteristics of phase and group velocity surfaces in anisotropic media

Stovas

Roganov²,

Roganov

2020

Geophysical Prospecting

Self Cite

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The phase and group velocity surfaces are essential for wave propagation in anisotropic media. These surfaces have certain features that, especially, for shear waves result in complications for modelling and inversion of recorded wavefields. To analyse wave propagation in an anisotropic model, it is important to identify these features in both the phase and group domains. We propose few characteristics for this analysis: the energy flux angle, decomposed in the polar and azimuth angle correction angles and enhancement factor, which is able to characterize both singularity points and triplication zones. The very simple equation that controls the triplications is derived in the phase domain. The proposed characteristics are illustrated for elastic and acoustic anisotropic models of different symmetry classes.

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Section: Figure 13mentioning

confidence: 66%

“…In this case, the stiffness coefficient matrix takes the form (Abedi et al., 2019)

\begin{matrix} left c_{jj} = & left \{\begin{matrix} v_{j}^{2}, j = 1, 2, 3 \\ 0, j = 4, 5, 6 \end{matrix} \\ left c_{j k} = & left \frac{v_{j} v_{k}}{\sqrt{1 + 2 η_{l}}}, j, k, l = 1, 2, 3; j \neq k \neq l, \end{matrix}

where

v_{j}

Section: Geometrical Characteristicsmentioning

confidence: 67%

“…The enhancement factor for acoustic ORT can be seen in Figure 5. The singularity point is clearly seen at phase angles

θ = 62 . 1^{\circ}

and

ϕ = 16 . 8^{\circ}

(the position can be computed analytically, see Xu and Stovas (2019b)) for both S1 and S2 waves. The cusps are identified at

ϕ = 0

and

θ = 90^{\circ}

and

ϕ = 90^{\circ}

and

θ = 90^{\circ}

for the S1 wave.…”

Section: Geometrical Characteristicsmentioning

confidence: 99%

See 1 more Smart Citation

Geometrical characteristics of phase and group velocity surfaces in anisotropic media

Stovas

Roganov²,

Roganov

2020

Geophysical Prospecting

Self Cite

View full text Add to dashboard Cite

show abstract

On the singularity point in acoustic orthorhombic media

Stovas

2024

Journal of Geophysics and Engineering

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The acoustic orthorhombic model is widely used in seismic modelling and processing of P wave data. However, the anisotropic acoustic models have so called S-wave artifacts (1 artifact in transversely isotropic acoustic medium and 2 artifacts in orthorhombic acoustic medium). I show that S wave artifacts can have one singularity point which results in complications in polarization field and the group velocity surface. The conditions of the existence of this point are defined in terms of anellipticity parameters. This singularity point and its group velocity image are the objects of my analysis.

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Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media

Stovas

2021

GEOPHYSICS

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Characterizing the kinematics of seismic waves in elastic vertical transversely isotropic (VTI) media involves four independent parameters. To reduce the complexity, the acoustic approximation for P-waves reduces the number of required parameters to three by setting the vertical S-wave velocity to zero. However, since only the SV-wave phase velocities parallel or perpendicular to the symmetry axis are indirectly set to zero, the acoustic approximation leads to coupled P-wave components and SV-wave artifacts. The new acoustic approximation suggests setting the vertical S-wave velocity as a phase angle-dependent variable so that the SV-wave phase velocity is zero at all phase angles. We find that manipulating this parameter is a valid way for P-wave approximation, but doing so inevitably leads to zero- or non-zero-valued spurious SV-wave components. Thus, we have developed a novel approach to efficiently approximate and thoroughly separate the two wave modes in VTI media. First, the exact P- and SV-wave phase velocity expressions are rewritten by introducing an auxiliary function. After confirming the insensitivity of this function, we construct a new expression for it and obtain simplified P- and SV-wave phase velocity expressions, which are three- and four-parameter, respectively. This approximation process leads to the same reasonable error for both wave modes. Accuracy analysis indicates that for the P-wave, the overall accuracy performance of our approach is comparable to that of some existing three-parameter approximations. We then derive the corresponding P- and SV-wave equations in tilted transversely isotropic (TTI) media and provide two available solutions, the hybrid finite-difference/pseudo-spectral scheme and the low-rank approach. Numerical examples illustrate the separability and high accuracy of the proposed P- and SV-wave simulation methods in TTI media.

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The kinematics of S waves in acoustic orthorhombic media

Cited by 9 publications

References 41 publications

Geometrical characteristics of phase and group velocity surfaces in anisotropic media

Geometrical characteristics of phase and group velocity surfaces in anisotropic media

On the singularity point in acoustic orthorhombic media

Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media

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