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Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media

Bowen Li and Alexey Stovas
Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media
Geophysics (August 2021) 86 (4): C133-C142

Abstract

Characterizing the kinematics of seismic waves in elastic vertical transversely isotropic (VTI) media involves four independent parameters. To reduce the complexity, the acoustic approximation for P-waves reduces the number of required parameters to three by setting the vertical S-wave velocity to zero. However, because only the SV-wave phase velocities parallel or perpendicular to the symmetry axis are indirectly set to zero, the acoustic approximation leads to coupled P-wave components and SV-wave artifacts. The new acoustic approximation suggests setting the vertical S-wave velocity as a phase angle-dependent variable so that the SV-wave phase velocity is zero at all phase angles. We find that manipulating this parameter is a valid approach for P-wave approximation but doing so inevitably leads to zero- or nonzero-valued spurious SV-wave components. Thus, we have developed a novel approach to efficiently approximate and thoroughly separate the two wave modes in VTI media. First, the exact P- and SV-wave phase velocity expressions are rewritten by introducing an auxiliary function. After confirming the insensitivity of this function, we construct a new expression for it and obtain simplified P- and SV-wave phase velocity expressions, which are three and four parameters, respectively. This approximation process leads to the same reasonable error for both wave modes. Accuracy analysis indicates that, for the P-wave, the overall accuracy performance of our approach is comparable to that of some existing three-parameter approximations. We then derive the corresponding P- and SV-wave equations in tilted transversely isotropic (TTI) media and provide two available solutions, the hybrid finite-difference/pseudospectral scheme and the low-rank approach. Numerical examples illustrate the separability and high accuracy of the proposed P- and SV-wave simulation methods in TTI media.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 86
Serial Issue: 4
Title: Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media
Affiliation: Norwegian University of Science and Technology, Department of Geoscience and Petroleum, Trondheim, Norway
Pages: C133-C142
Published: 202108
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 54
Accession Number: 2021-050863
Categories: Applied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 202116
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