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From this viewpoint, the deviation term of Muir's approximation can be put into the form
| |
(4) |

This equation also has zero value in the vertical and horizontal directions and maximum value near 45 degrees because it contains the , but has a kind of weighting along the angle that causes a little movement of the maximum value according to the anisotropy factor, defined as the horizontal to vertical phase velocity ratio . In this case the ray velocity can be represented by
| |
(5) |

Figure 2 and Figure 3 show how well these two approximations for deviation term fit to the deviation from the best fitting ellipse in the cases of weak and moderate anisotropy, respectively.

** Next:** NON-HYPERBOLIC MOVEOUT EQUATIONS
** Up:** ANELLIPTIC APPROXIMATION
** Previous:** Byun's approximation
Stanford Exploration Project

1/13/1998