Prestack depth migration methods include two categories. One is kirchhoff method based on high-frequency
approximate solution of wave equation, the other is differential method based on the finite difference
solution or mixed-domain solution of wave equation. Gaussian beam method is between them and is used
for wave propagation chracterization and imaging. The problem of Gaussian beam method is that too many
approximations are introduced when characterizing the wave propagation in the ray-centered coordinates.
In addition to high-frequency approximation, the amplitudes of wave field whose plane is perpendicular to
any point of the ray path is merely derived from the amplitude Gauss attenuation of that point, which is too
simple to characterize the complex wave phenomena. Therefore, we derived the one-way wave equation in
ray-centered coordinates and used the equation to extrapolate wave field in ray beam to accurately
characterize local wave field. The method preserves the flexibility of ray method and the accuracy of wave
equation method to describe the wave field within certain ray beams. Compared with simple ray theory and
complex wave equation theory, the method makes a compromise between the flexibility and accuracy. It can
be used to complex subsurface structure imaging and tomography velocity estimation more conveniently.
Numerical examples demonstrate the correctness of the method.
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