| Summary: | I consider three different, but important, types of anisotropic material: First, for transverse isotropic media with a vertical axis of symmetry (TIV), I investigate the effects of dip on the travel time for imaging purposes. Secondly, transverse isotropic media with a horizontal axis of symmetry (TIH) are used as a model for a vertically fractured materials; I extend existing techniques for fracture strike estimation to dipping layers. Finally, for a combination TIV and TIH media, which represents orthorhombic symmetry, analysis of the AVO behaviour leads to an inversion procedure for crack density. For a dipping TIV layer I show that the travel time can be decomposed into structure- and anisotropy-independent parts. A thorough investigation using synthetic seismograms reveals that this separation is valid for up to 15% P-wave anisotropy and dip angles of up to 20 degrees. I propose an additional processing step to enhance seismic data if anisotropy and dip both are present. I extend an estimation method for the fracture strike in a TIH medium to dipping layers. An analytical analysis shows that the application of a non-linear global optimization scheme is required to invert the strike direction satisfactorily. This new method is applied to a real data set, and the general trend of the regional strike direction is confirmed. The third type of anisotropy (orthorhombic), is investigated its dynamic response. A derivation of all pure and mode-converted reflection coefficients is followed by a separation approach to extract the crack-dependent contribution. I demonstrate that a special acquisition geometry can lead to the inversion of the parameter crack density.
|
|---|
