| Popis: |
In the recent years, idea of layer stripping method has proved to be useful in obtaining elastic parameters for one dimensional media. The idea was first pointed out to seismologist by Bube and Burridge (1983) to obtain impedance contrasts from normal incidence data, and was further extended to multiparameters by Singh et al. (1989) in the τ-p domain. The theory should be extended to multidimensional case, but coupling of different ray parameters in the τ-p domain for laterally inhomogeneous media pose problems. One of the way to decouple these ray parameters is to assume that the medium parameters are smoothly varying in the horizontal directions and are small deviations from the vertical, and then use the WKBJ theory to obtain the causal time (a key point to the layer stripping methods), which allows propagation of surface wavefield downwards and construction of the model parameters. The basic physical assumption in formulating the inverse solution is that the change in amplitude of a plane wave at the causal time is related to the change of the elastic moduli at the spatial position of the plane wave. |
