<i>P-SV</i> reflection moveouts for transversely isotropic media with a vertical symmetry axis

Seriff, A. J.; Sriram, K.P.

doi:10.1190/1.1443148

Cited by 33 publications

(19 citation statements)

References 6 publications

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“…Various aspects of PS-wave kinematics in this special case were discussed for isotropic media by Tessmer and Behle (1988), and for anisotropic media by Seriff and Sriram (1991), Tsvankin and Thomsen (1994), Grechka et al (1999a), Thomsen (1999), and others; most of these results are summarized in Tsvankin (2005). Conventional-spread PS-wave moveout for such stratified models with a horizontal symmetry plane is controlled primarily by the NMO ellipse.…”

Section: Properties Of Reflected Ps-wavesmentioning

confidence: 96%

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Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Tsvankin¹,

Grechka²

2011

183

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Section: Properties Of Reflected Ps-wavesmentioning

confidence: 96%

“…Hence, moveout analysis on moderate spreads can provide the vertical traveltime (t P S0 ) and the NMO velocity (V nmo,P S ) of PS-waves. The NMO velocities of pure and converted modes are related by the following Dix-type equation (Seriff and Sriram, 1991;Tsvankin, 2005):…”

Section: Feasibility Of the Inversion Proceduresmentioning

confidence: 99%

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Tsvankin¹,

Grechka²

2011

183

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“…The exploration depth and the S-wave velocity of the lower half space are initial model parameters invariably difficult to estimate accurately but necessary for accurate inversion of Rayleigh waves. Additionally, imaging the subsurface structure using converted waves (e.g., PS waves) has been a topic of interest in the petroleum industry for more than a decade (e.g., SERIFF and SRIRAM, 1991;GRECHKA and TSVANKIN, 2002). Imaging the deep subsurface structures via converted waves requires knowledge of the near-surface S-wave velocity field that is difficult to estimate by conventional oil exploration seismic reflection technologies.…”

Section: Introductionmentioning

confidence: 99%

Approximation to Cutoffs of Higher Modes of Rayleigh Waves for a Layered Earth Model

Xia

Miller

2009

Pure appl. geophys.

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A cutoff defines the long-period termination of a Rayleigh-wave higher mode and, therefore is a key characteristic of higher mode energy relationship to several material properties of the subsurface. Cutoffs have been used to estimate the shear-wave velocity of an underlying half space of a layered earth model. In this study, we describe a method that replaces the multilayer earth model with a single surface layer overlying the half-space model, accomplished by harmonic averaging of velocities and arithmetic averaging of densities. Using numerical comparisons with theoretical models validates the single-layer approximation. Accuracy of this single-layer approximation is best defined by values of the calculated error in the frequency and phase velocity estimate at a cutoff. Our proposed method is intuitively explained using ray theory. Numerical results indicate that a cutoffs frequency is controlled by the averaged elastic properties within the passing depth of Rayleigh waves and the shear-wave velocity of the underlying half space.

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“…If pure shear waves are not excited, the SV‐wave NMO velocity can be determined from the NMO velocities of the P‐ and converted PSV‐waves (here denoted simply as PS) in the following way ( Seriff and Sriram 1991):…”

Section: Introductionmentioning

confidence: 99%

“…Tessmer and Behle 1988; Alfaraj 1993). Equation (5) for the NMO velocity of PS‐waves in horizontally layered VTI media was first given by Seriff and Sriram (1991). Tsvankin and Thomsen (1994) presented an analytic expression for the quartic moveout term of PS conversions for vertical transverse isotropy and used it to describe non‐hyperbolic (long‐spread) reflection moveout.…”

Section: Introductionmentioning

confidence: 99%

Dip moveout of converted waves and parameter estimation in transversely isotropic media

Tsvankin

Grechka

2000

Geophysical Prospecting

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For transverse isotropy with a vertical symmetry axis (VTI media), P‐wave reflection data alone are insufficient for building velocity models in depth. Here, we show that all parameters of VTI media responsible for propagation of P‐ and SV‐waves (the P‐wave and S‐wave vertical velocities VP0 and VS0 and the anisotropic parameters ε and δ) can be obtained by combining P‐wave traveltimes with the moveout of PS‐waves converted at a horizontal and dipping interface. Using converted modes, rather than pure S‐waves, avoids the need for expensive shear‐wave excitation on land and makes the method suitable for offshore exploration. The inversion algorithm is based on a new analytic description of the dip moveout of PS‐waves developed for symmetry planes of anisotropic media (and for any vertical plane in models with weak azimuthal anisotropy). The common‐midpoint (CMP) traveltime–offset relationship, derived in a parametric form and represented through the components of the slowness vector of the P‐ and S‐waves, makes it possible to compute the moveout curve of the PS‐wave without two‐point ray tracing. This formalism also leads to closed‐form solutions for moveout attributes, such as the coordinates (xmin, tmin) of the traveltime minimum, the normal‐moveout (NMO) velocity defined at x = xmin and the slope of the moveout curve (apparent slowness) at zero offset. The parameter‐estimation algorithm operates with reflection moveout of P‐ and PS‐waves from a horizontal and dipping reflector. The NMO velocities of P‐ and PS‐waves from horizontal events and the ratio of the corresponding zero‐offset traveltimes yield three equations for the four unknown medium parameters. The remaining parameter is found from an overdetermined system of equations that includes the P‐wave NMO velocity and moveout attributes of the PS‐wave for a dipping event. Numerical analysis shows that the PS‐wave dip‐moveout signature plays a crucial role in obtaining accurate estimates of the anisotropic parameters. The joint inversion of P and PS data provides the necessary information not only for P‐wave depth imaging in VTI media, but also for the processing of PS‐waves, including re‐sorting of PS traces into common‐reflection‐point gathers and transformation to zero offset (TZO).

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P-SV reflection moveouts for transversely isotropic media with a vertical symmetry axis

Cited by 33 publications

References 6 publications

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Approximation to Cutoffs of Higher Modes of Rayleigh Waves for a Layered Earth Model

Dip moveout of converted waves and parameter estimation in transversely isotropic media

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