Apparent axial properties of transversely isotropic media

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 1012-1013 ◽  
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.

SH waves in layered transversely isotropic media—a wave approach

1979 ◽  
Vol 16 (10) ◽  
pp. 1998-2008 ◽  
Author(s):  
P. F. Daley ◽  
F. Hron
Keyword(s):  
Layered Medium ◽  
Transversely Isotropic ◽  
Integral Transforms ◽  
Earth Model ◽  
Sh Waves ◽  
Transversely Isotropic Media ◽  
Head Waves ◽  
Isotropic Media ◽  
Ray Series ◽  
Insight Into

There are many reports in the literature of anomalies in traveltime data when an isotropic homogeneous Earth model is used to interpret field data. In several cases, the introduction of a layered transversely isotropic model has successfully explained these kinematic irregularities. However, it is useful, in fact essential, to confirm the kinematic fit with a dynamic (amplitude) comparison.In this paper the problem of SH waves propagating in a transversely isotropic plane layered medium is discussed through the use of integral transforms and evaluation by steepest descents. This procedure yields not only the asymptotic solution which is also attainable using an asymptotic ray series approach, but also allows for the investigation of the interference of the reflected and head waves in the vicinity of the critical point (point of critical refraction). It is in this region that asymptotic ray theory breaks down or at least introduces significant error in the displacement amplitudes.It can be shown that a simple transformation will reduce this problem to one that may be solved exactly by the Cagnaird de Hoop technique but it is instructive to examine nonspherical wave-fronts in order to obtain an insight into more complicated anisotropic media.

Seismic parameters for transversely isotropic media

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 1908-1914 ◽  
Author(s):  
Bok S. Byun
Keyword(s):  
Velocity Structure ◽  
Transversely Isotropic ◽  
Wave Surface ◽  
Seismic Parameters ◽  
Transversely Isotropic Media ◽  
Isotropic Media ◽  
The Media ◽  
Local Properties ◽  
Exploration Seismology ◽  
Seismic Measurements

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.

Reverse time migration in tilted transversely isotropic media

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.

Variation of stacking velocity in transversely isotropic media

1995 ◽  
Vol 26 (2-3) ◽  
pp. 431-436 ◽  
Author(s):  
Patrick N.(Jr). Okoye ◽  
N. F. Uren ◽  
W. Waluyo
Keyword(s):  
Transversely Isotropic ◽  
Transversely Isotropic Media ◽  
Isotropic Media

Elastic Least-Squares Imaging in Tilted Transversely Isotropic Media for Multicomponent Land and Pressure Marine Data

2020 ◽  
Vol 41 (4) ◽  
pp. 805-833 ◽  
Author(s):  
Jidong Yang ◽  
Biaolong Hua ◽  
Paul Williamson ◽  
Hejun Zhu ◽  
George McMechan ◽  
...  
Keyword(s):  
Least Squares ◽  
Transversely Isotropic ◽  
Transversely Isotropic Media ◽  
Isotropic Media ◽  
Marine Data

Transverse isotropy of the upper mantle in the vicinity of Pacific fracture zones

1969 ◽  
Vol 59 (1) ◽  
pp. 59-72
Author(s):  
Robert S. Crosson ◽  
Nikolas I. Christensen
Keyword(s):  
Upper Mantle ◽  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Transversely Isotropic ◽  
Seismic Wave Propagation ◽  
Fracture Zones ◽  
Mantle Material ◽  
Transversely Isotropic Media ◽  
Horizontal Symmetry ◽  
Isotropic Media

Abstract Several recent investigations suggest that portions of the Earth's upper mantle behave anisotropically to seismic wave propagation. Since several types of anisotropy can produce azimuthal variations in Pn velocities, it is of particular geophysical interest to provide a framework for the recognition of the form or forms of anisotropy most likely to be manifest in the upper mantle. In this paper upper mantle material is assumed to possess the elastic properties of transversely isotropic media. Equations are presented which relate azimuthal variations in Pn velocities to the direction and angle of tilt of the symmetry axis of a transversely isotropic upper mantle. It is shown that the velocity data of Raitt and Shor taken near the Mendocino and Molokai fracture zones can be adequately explained by the assumption of transverse isotropy with a nearly horizontal symmetry axis.

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