


 Simulating propagation of separated wave modes in general anisotropic media, Part I: qPwave propagators  

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Published as Geophysics, 79, no. 1, C1C18, (2014)
Simulating propagation of separated wave modes in general anisotropic media, Part I: qPwave propagators
Jiubing Cheng^{}and Wei Kang^{}
^{}State Key Laboratory of Marine Geology, Tongji University, Shanghai, China. Email: cjb1206@tongji.edu.cn
^{}School of Ocean and Earth Science, Tongji University, Shanghai, China. Email: w.kang_1986@hotmail.com
Abstract:
Wave propagation in an anisotropic medium is inherently described by elastic wave equations, with P and Swave modes
intrinsically coupled. We present an approach to simulate propagation of separated wave modes for
forward modeling,
migration, waveform inversion and other applications in general anisotropic media.
The proposed approach consists of two cascaded computational steps. First, we simulate equivalent
elastic anisotropic wavefields with a minimal secondorder coupled system
(that we call here a pseudopuremode wave equation),
which describes propagation of all wave modes with a partial wave mode separation. Such a system for qPwave
is derived from the inverse Fourier transform of the Christoffel equation after a
similarity transformation, which aims to project the original vector displacement wavefields onto isotropic
references of the polarization directions of qPwaves. It accurately describes the kinematics
of all wave modes and enhances qPwaves when the pseudopuremode wavefield components are summed.
The second step is a filtering to further project the pseudopuremode wavefields onto the polarization directions
of qPwaves so that residual qSwave energy is removed and scalar qPwave fields are accurately separated
at each time step during wavefield extrapolation.
As demonstrated in the numerical examples, pseudopuremode wave equation plus
correction of projection deviation provides a robust and flexible
tool for simulating propagation of separated wave modes in
transversely isotropic and orthorhombic media.
The synthetic example of Hess VTI model shows that
the pseudopuremode qPwave equation can be used in prestack reversetime migration (RTM) applications.



 Simulating propagation of separated wave modes in general anisotropic media, Part I: qPwave propagators  

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