Slowness‐domain kinematical characteristics for horizontally layered orthorhombic media. Part I: Critical slowness match

Ravve, Igor; Koren, Zvi

doi:10.1111/1365-2478.12765

Cited by 5 publications

(2 citation statements)

References 54 publications

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“…The propagation of waves within anisotropic elastic media is a complex research topic (Yilmaz, 2001). With respect to the kinematic characteristics of waves in anisotropic media, curvatures of the slowness surface are essential in many geophysical applications such as velocity analysis, modelling and post-stack time migration (Alkhalifah, 1997;Červený, 2001;Chopra & Marfurt, 2007;Grechka, 2017;Ravve & Koren, 2019;Stovas & Alkhalifah, 2013;Stovas et al, 2021a;Tsvankin, 2012). The slowness surface (vertical slowness with respect to two horizontal projections) is essential for seismic data processing at an early stage such as velocity analysis and phase-shift migration (Stovas & Roganov, 2009).…”

Section: Introductionmentioning

confidence: 99%

Umbilic points of slowness surface in elastic orthorhombic media

Xu¹,

Stovas²,

Huang

2023

Geophysical Prospecting

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For 3D seismic data processing, azimuth plays an important role, especially in complex subsurface regions. In such regions, elliptical or anelliptical orthorhombic models are commonly used to describe wave propagation. In these models, the behaviour of the slowness surface needs more detailed analysis. Umbilic points defined by the equal principal curvatures exist in a complex 3D model. In the vicinity of the umbilic points, the traveltime surface has the shifted hyperbola form that needs to be considered in processing operations like velocity analysis. Fractured media characterized by the orthorhombic model are more likely to have umbilic points, and it is important to address their positions. If exists, umbilic points can provide additional constraints in inverting for model parameters. Through a defined condition, we examine the position of the umbilic point and derive their explicit formulas. We analyse umbilic points for elliptical and anelliptical orthorhombic models in the numerical example. For the elliptical orthorhombic model, the formulas for the umbilic point position on different symmetry planes are derived and corresponding conditions are also identified. Further, we numerically examine umbilic point positions for anelliptical orthorhombic models and observe that the umbilic points are located out of two vertical symmetry planes. Moreover, caused by interference from two neighbouring umbilic points, a more significant deviation in traveltime is found in the anelliptical orthorhombic model.

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Section: Introductionmentioning

confidence: 99%

Umbilic points of slowness surface in elastic orthorhombic media

Xu¹,

Stovas²,

Huang

2023

Geophysical Prospecting

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“…The approximations for relative geometrical spreading are proposed in VTI (Xu and Stovas ) and ORT model (Xu and Stovas ; Xu, Stovas and Sripanich ) under the acoustic assumption. The slowness domain kinematical characteristics for horizontally layered ORT media are discussed by Ravve and Koren (). Similar to the acoustic VTI case, the artefacts, referred as ‘S waves’ although they are different with the S waves defined by the polarization, also remain in the acoustic ORT model, which behaviour is much more complicated, and no research related to this aspect is discussed.…”

Section: Introductionmentioning

confidence: 99%

The kinematics of S waves in acoustic orthorhombic media

Stovas

2019

Geophysical Prospecting

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Orthorhombic models are often used in the seismic industry nowadays to describe azimuthal and polar anisotropy and reasonably realistic in capturing the features of the earth interior. It is challenging to handle so many model parameters in the seismic data processing. In order to reduce the number of the parameters for P wave, the acoustic orthorhombic medium is proposed by setting all on‐axis S wave velocities to zero. However, due to the coupled behaviour for P and S waves in the orthorhombic model, the ‘S wave artefacts’ are still remained in the acoustic orthorhombic model, which kinematics needs to be defined and analysed. In this paper, we analyse the behaviour of S wave in acoustic orthorhombic media. By analysis of the slowness surface in acoustic orthorhombic media, we define the S waves (or S wave artefacts) that are more complicated in shape comparing to the one propagating in an acoustic transversely isotropic medium with a vertical symmetry axis. The kinematic properties of these waves are defined and analysed in both phase and group domain. The caustics, amplitude and the multi‐layered case for S wave in acoustic orthorhombic model are also discussed. It is shown that there are two waves propagating in this acoustic orthorhombic medium. One of these waves is similar to the one propagating in acoustic vertical symmetry axis media, whereas another one has a very complicated shape consisting of two crossing surfaces.

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On-axis triplications in elastic orthorhombic media

Stovas

Mikada

et al. 2020

Geophysical Journal International

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Summary Triplicated traveltime curve has three arrivals at a given distance with the bowtie shape in the traveltime-offset curve. The existence of the triplication can cause a lot of problems such as several arrivals for the same wave type, anomalous amplitudes near caustics, anomalous behavior of rays near caustics, which leads to the structure imaging deviation and redundant signal in the inversion of the model parameters. Hence, triplication prediction becomes necessary when the medium is known. The research of the triplication in transversely isotropic medium with a vertical symmetry axis (VTI) has been well investigated and it has become clear that, apart from the point singularity case, the triplicated traveltime only occurs for S wave. On contrary to the VTI case, the triplication behavior in the orthorhombic (ORT) medium has not been well focused due to the model complexity. In this paper, we derive the second-order coefficients of the slowness surface for two S waves in the vicinity of three symmetry axes and define the elliptic form function to examine the existence of the on-axis triplication in ORT model. The existence of the on-axis triplication is found by the sign of the defined curvature coefficients. Three ORT models are defined in the numerical examples to analyze the behavior of the on-axis triplication. The plots of the group velocity surface in the vicinity of three symmetry axes are shown for different ORT models where different shapes: convex or the saddle-shaped (concave along one direction and convex along with another) indicates the existence of the on-axis triplication. We also show the traveltime plots (associated with the group velocity surface) to illustrate the effect of the on-axis triplication.

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Slowness‐domain kinematical characteristics for horizontally layered orthorhombic media. Part I: Critical slowness match

Cited by 5 publications

References 54 publications

Umbilic points of slowness surface in elastic orthorhombic media

Umbilic points of slowness surface in elastic orthorhombic media

The kinematics of S waves in acoustic orthorhombic media

On-axis triplications in elastic orthorhombic media

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