Velocity analysis based on minimum entropy

Vries, Diemer de

doi:10.1190/1.1441629

Cited by 35 publications

(12 citation statements)

References 44 publications

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“…The methods described in the previous sections will be illustrated by an example which is commonly used to show the validity of a method (e.g., in [8]). The physical experiment of the example is illustrated in Fig.…”

Section: Simulation Examplesmentioning

confidence: 99%

“…The knowledge of the correct wave propagation velocity is needed for the application of the operator (9). If the wrong propagation velocity is used, the results of the downward wavefield extrapolation are not well focused [8]. Thus, the determination of the correct wave propagation velocity is crucial for the quality of the results of the downward wavefield extrapolation.…”

Section: Introduction Avefield Measurements and The Wave Equationmentioning

confidence: 99%

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Bayesian estimation of medium properties in wavefield downward extrapolation problems

Pitas¹,

Venetsanopoulos²

1988

IEEE Trans. Acoust., Speech, Signal Processing

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Acoustic waves are used in many areas (ultrasonic medicine, geophysical oil prospecting, etc.) for nondestructive imaging of the interior of objects such as the earth, the human body, etc. The wavefield measurements recorded on the surface of the object are extrapolated according to the wave equation to give an "image" of the object by using an imaging principle. The extrapolation propagates backward the noise present in the measurements. Thus, the quality of the final image is deteriorated, unless statistical restoration techniques are used. Another source of degradation of the image is the insufficient knowledge of some properties of the medium such as the wave propagation velocity. The aim of this work is to use estimation theory to determine good estimates of the velocity and of the backward extrapolated wavefield from the known surface wavefield measurements.

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Section: Simulation Examplesmentioning

confidence: 99%

Section: Introduction Avefield Measurements and The Wave Equationmentioning

confidence: 99%

Bayesian estimation of medium properties in wavefield downward extrapolation problems

Pitas¹,

Venetsanopoulos²

1988

IEEE Trans. Acoust., Speech, Signal Processing

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“…Diffraction events produced by discontinuities (e.g., faults, fractures, and other geologic features) and strong heterogeneities have been employed to refine isotropic velocity models. For example, local slant-stacks (Harlan et al, 1984) and the minimum entropy (ME) norm (De Vries and Berkhout, 1984) were applied to focus diffractions on common-offset (poststack) sections and perform isotropic velocity analysis. Söllner et al (2002) extend the focusing-based normal-moveout velocity analysis of diffractions to 3D common-offset sections.…”

Section: Introductionmentioning

confidence: 99%

Analysis of diffractions in dip-angle gathers for transversely isotropic media

Arora

Tsvankin

2017

SEG Technical Program Expanded Abstracts 2017

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Diffractions can supplement reflected waves in anisotropic velocity analysis because they increase the aperture and may illuminate parts of the model that do not produce strong reflections. However, enhancement of diffractions and their separation from the more intensive reflections remains a challenging task, especially if the velocity model is not sufficiently accurate. Here, we construct dip-angle common-image gathers (CIGs) for transversely isotropic (TI) media using Kirchhoff migration. Dip-angle gathers can be conveniently used to generate diffraction-based depth images if a sufficiently accurate velocity model is available. We also analyze the moveout distortions of diffraction and reflection events in dip-angle CIGs in the presence of errors in the TI parameters. The residual moveout of diffractions computed from dip-angle gathers can be employed in migration velocity analysis (MVA) to refine the anisotropic velocity model.

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“…Various methods have been proposed for improving the resolution of stacking velocity analysis (e.g., Kirling et al, 1984;de Vries and Berkhout, 1984;Toldi, 1989;Biondi and Kostov, 1989). They typically require specific information about the reflections and are computationally more intensive than is conventional velocity analysis.…”

Section: Introductionmentioning

confidence: 99%

Selective-correlation velocity analysis

Larner

Celis

2007

GEOPHYSICS

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The need for increased resolution in velocity spectra is clear when one wishes to distinguish between neighboring primary events from reflectors with conflicting dip, or to identify primaries in the presence of multiples. The transformation in velocity analysis from the offset and reflection-time domain to the stacking velocity and zero-offset-time domain can be achieved using any of several coherence measures based on the crosscorrelations between traces in a collection such as a common-midpoint (CMP) gather or common-image gather (CIG). Use of selected subsets of crosscorrelations, rather than all possible ones in a gather, however, can improve both the reliability and resolution of velocity analysis. In selective-correlation velocity analysis, we include in the summation only those crosscorrelations for whose pair of traces the relative differential moveout of reflections exceeds a chosen threshold value. Comparisons of the performances on synthetic CMP gathers show that selective-correlation velocity analysis considerably enhances the resolving power of velocity spectra over that of conventional crosscorrelation sum (whether normalized or unnormalized) in the presence of closely interfering reflections, statics distortions and random noise, at no sacrifice in the quality of results, and does so at computational cost that is comparable to that for conventional velocity analysis.

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Velocity analysis based on minimum entropy

Cited by 35 publications

References 44 publications

Bayesian estimation of medium properties in wavefield downward extrapolation problems

Bayesian estimation of medium properties in wavefield downward extrapolation problems

Analysis of diffractions in dip-angle gathers for transversely isotropic media

Selective-correlation velocity analysis

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