Elastic wave-mode separation for TTI media |

I also extend the wave-mode separation to 3D TI models. The P-mode separators can be constructed by solving the Christoffel equation for the P-wave eigenvectors with local medium parameters. The SV and SH separators are constructed using the mutual orthogonality among P, SV, and SH modes. For the three modes, there are a total number of nine separators, with three components for each mode. The separators vary according to the medium parameters , , anisotropy parameters and and tilt and azimuth of the symmetry axis. The P-wave separators are constructed under no kinematic assumptions, and amplitudes of P-mode correctly characterize the plane-wave solution. Shear wave separators are constructed under kinematic assumptions, and therefore the amplitudes of shear modes are inaccurate in the singular directions. Nevertheless, the proposed technique successfully separates fast and slow shear wavefields. The process of constructing 3D separators and separating wave-modes in 3D eliminates the step of decomposing the wavefields into symmetry planes, which only works for models with an invariant symmetry axis. Spatially-varying 3D separators have potential benefits for complex models and can be used to separate wave-modes in elastic reverse time migration (RTM) for TTI models. The spatially-varying 3D separators imply large computational and storage cost, and therefore, a more efficient separation method, such as the proposed table look-up alternative, is necessary for a successful implementation.

Elastic wave-mode separation for TTI media |

2013-08-29