Seismic parameters for transversely isotropic media

One of the most important problems in exploration seismology is to relate the surface seismic measurements with the subsurface geologic parameters. The concept of wavefront curvature has been in extensive use for this purpose. Byun (1982) developed relationships between several measurable seismic parameters (e.g., geometrical spreading and normal moveout velocity) and parameters of the media with elliptical velocity dependencies. This paper extends the wavefront curvature concept to more general, transversely isotropic media. After a brief discussion on ray tracing, a procedure is developed to describe the local properties of the ray based on an elliptical surface fit to the actual wave surface. The apparent velocities of the elliptical fit are then used to generalize the seismic parameters developed in Byun (1982). Simple numerical experiments are given to demonstrate the explorational significance of the theory. It is shown that the measurements of the normal moveout velocity are not sufficient to estimate the velocity structure of the transversely isotropic medium. The “side‐slip” effect can lead to significant errors in depth‐mapping dipping reflectors.

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Seismic parameters for transversely isotropic media

Exploration Geophysics ◽

10.1071/eg984264b ◽

1984 ◽

Vol 15 (4) ◽

pp. 264-264

Author(s):

B. S. Byun

Keyword(s):

Transversely Isotropic ◽

Seismic Parameters ◽

Transversely Isotropic Media ◽

Isotropic Media

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Nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media

Geophysics ◽

10.1190/1.2910827 ◽

2008 ◽

Vol 73 (4) ◽

pp. D17-D33 ◽

Cited By ~ 31

Author(s):

Bing Zhou ◽

Stewart Greenhalgh ◽

Alan Green

Keyword(s):

Seismic Tomography ◽

Velocity Structure ◽

Body Wave ◽

Transversely Isotropic ◽

The Body ◽

Body Waves ◽

Inversion Method ◽

Perturbation Equation ◽

Transversely Isotropic Media ◽

Isotropic Media

Crosshole seismic tomography often is applied to image the velocity structure of an interwell medium. If the rocks are anisotropic, the tomographic technique must be adapted to the complex situation; otherwise, it leads to a false interpretation. We propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes. This method is based on a new version of the first-order traveltime perturbation equation. It directly uses the derivative of the phase velocity rather than the eigenvectors of the body-wave modes to overcome the singularity problem for application to the two quasi-shear waves. We applied an iterative nonlinear solver incorporating our kinematic ray-tracing scheme and directly compute the Jacobian matrix in an arbitrary reference medium. This reconstructs the five elastic moduli or Thomsen parameters from the first-arrival traveltimes of the three seismic body waves (qP, qSV, qSH) in strongly and weakly anisotropic media. We conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock, reconstructing a fault embedded in a strongly anisotropic background, and imaging a complicated four-layer model containing a small channel and a buried dipping interface. We compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme, which showed the capability and superiority of the new scheme for crosshole tomographic imaging.

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Seismic parameters for transversely isotropic media

10.1190/1.1894120 ◽

1984 ◽

Author(s):

Bok Sub Byun

Keyword(s):

Transversely Isotropic ◽

Seismic Parameters ◽

Transversely Isotropic Media ◽

Isotropic Media

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Velocity analysis in transversely isotropic media

Geophysics ◽

10.1190/1.1441110 ◽

1980 ◽

Vol 45 (6) ◽

pp. 1094-1095 ◽

Cited By ~ 2

Author(s):

A. L. Lucas ◽

P. N. S. O’Brien ◽

J. H. Thomas

Keyword(s):

Transversely Isotropic ◽

Vertical Axis ◽

Two Dimensions ◽

P Wave ◽

Velocity Analysis ◽

Wave Surface ◽

Common Depth Point ◽

Transversely Isotropic Media ◽

Isotropic Media ◽

Ellipsoid Of Revolution

In transversely isotropic media, the moveout velocity obtained from common‐depth‐point (CDP) analysis may be significantly different from the horizontal velocity of the pseudo‐P wave. In Levin’s (1978) paper, he discusses, among other things, the problem of velocity determination in a medium in which the pseudo‐P wave surface produced by a point source is an ellipsoid of revolution. He points out that one would expect many sedimentary rocks to be transversely isotropic with a vertical axis of symmetry. In his Appendix he proves that an ellipse (using two dimensions for convenience) is one possible shape for the wave surface in such a medium. He also shows, as have others, that in this case CDP velocity analysis measures the velocity of horizontal propagation.

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Apparent axial properties of transversely isotropic media

Geophysics ◽

10.1190/1.1442140 ◽

1986 ◽

Vol 51 (4) ◽

pp. 1012-1013 ◽

Cited By ~ 4

Author(s):

Bok S. Byun ◽

Shi‐Chen W. Cheng

Keyword(s):

Transversely Isotropic ◽

Theoretical Development ◽

Energy Propagation ◽

Seismic Properties ◽

Transversely Isotropic Media ◽

Isotropic Media ◽

Local Properties ◽

Theoretical Insight ◽

Insight Into ◽

Made In

Byun (1984) described some important surface seismic characteristics (such as “apparent” velocities) for transversely isotropic media. His theoretical development was based on the elliptical surface fit to the actual wave surface of energy propagation from a point source to describe local properties of the ray. In this note we give more theoretical insight into the apparent axial properties of the surface observations made in Byun’s (1984) paper. More comprehensive studies were reported in Helbig (1983) and Hake et al. (1984) for other surface seismic properties of transversely isotropic media.

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Reverse time migration in tilted transversely isotropic media

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v38i2.2041 ◽

2020 ◽

Vol 38 (2) ◽

Author(s):

Razec Cezar Sampaio Pinto da Silva Torres ◽

Leandro Di Bartolo

Keyword(s):

Seismic Anisotropy ◽

Synthetic Data ◽

Transversely Isotropic ◽

Reverse Time ◽

Reverse Time Migration ◽

Computer Clusters ◽

Time Migration ◽

Transversely Isotropic Media ◽

Isotropic Media ◽

Tti Media

ABSTRACT. Reverse time migration (RTM) is one of the most powerful methods used to generate images of the subsurface. The RTM was proposed in the early 1980s, but only recently it has been routinely used in exploratory projects involving complex geology – Brazilian pre-salt, for example. Because the method uses the two-way wave equation, RTM is able to correctly image any kind of geological environment (simple or complex), including those with anisotropy. On the other hand, RTM is computationally expensive and requires the use of computer clusters. This paper proposes to investigate the influence of anisotropy on seismic imaging through the application of RTM for tilted transversely isotropic (TTI) media in pre-stack synthetic data. This work presents in detail how to implement RTM for TTI media, addressing the main issues and specific details, e.g., the computational resources required. A couple of simple models results are presented, including the application to a BP TTI 2007 benchmark model.Keywords: finite differences, wave numerical modeling, seismic anisotropy. Migração reversa no tempo em meios transversalmente isotrópicos inclinadosRESUMO. A migração reversa no tempo (RTM) é um dos mais poderosos métodos utilizados para gerar imagens da subsuperfície. A RTM foi proposta no início da década de 80, mas apenas recentemente tem sido rotineiramente utilizada em projetos exploratórios envolvendo geologia complexa, em especial no pré-sal brasileiro. Por ser um método que utiliza a equação completa da onda, qualquer configuração do meio geológico pode ser corretamente tratada, em especial na presença de anisotropia. Por outro lado, a RTM é dispendiosa computacionalmente e requer o uso de clusters de computadores por parte da indústria. Este artigo apresenta em detalhes uma implementação da RTM para meios transversalmente isotrópicos inclinados (TTI), abordando as principais dificuldades na sua implementação, além dos recursos computacionais exigidos. O algoritmo desenvolvido é aplicado a casos simples e a um benchmark padrão, conhecido como BP TTI 2007.Palavras-chave: diferenças finitas, modelagem numérica de ondas, anisotropia sísmica.

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