The characteristic equation describes the propagation of a discontinuity in space (x,y,z). Let us assume that equation can be solved with respect to t: and . Then we get from equation (20):
(21) |
That is exactly the Eikonal equation for a medium with elliptic anisotropy. In the case of isotropy, it follows that and equation (21) is reduced to
(22) |
Let us consider, for example, the linear acoustic equation