THE LARGE PERTURBATION INVERSION METHOD OF 2-D MEDIUM PARAMETERS

The problem of parameter inversion in an inhomogeneous medium was stud ied and a generalized ray approximation method to inverse the 2-D medi um parameters is introduced in this paper. By using referential and pe rturbational variables, the medium parameters of the wave equation hav e been rewritten. By using the Green function theory, the integral equ ation of perturbational parameters was obtained. Based on the local pr inciples of wave function and ray theory in inhomogeneous medium, a ge neralized ray approximation form of the total wave field is introduced . By defining the medium parameters function, attention has been focus ed on the Fredholm integral equation of the first kind. By using convo lution transforms, the solution of the medium parameters function in 2 -D medium was obtained. The perturbations of medium parameters are usu ally not greater than 20% in the Born weak scattering method. However, in this paper the numerical results show that when the perturbations of the medium parameters are within 50%, this method can effectively i nverse its variation. (C) 1997 Academic Press Limited.