Seismic anisotropy is drawing increased attention from academia and industry. This is due to advances in anisotropy parameter estimation, the wider offset and azimuthal coverage in 3D seismic surveys, and the use of anisotropic depth-velocity models in processing and inversion.
Similarly, in the efforts to extract more information about the properties of the subsurface, to record and analyze S-waves is also getting more common.
Seismic modelling is a key tool to understand and explore the potentials of the new techniques in seismic exploration. The NORSAR seismic ray-trace modelling is the most advanced and widely used ray-based seismic modelling package in the oil and gas industry. It is used extensively in planning of seismic surveys and in processing and analysis of seismic data.
As a response to the increasing interest in anisotropy as well as in S-wave propagation, NORSAR has conducted extensive research on ray-tracing in anisotropic media, including modelling of S-waves. The developed propagation techniques are very robust, and provide very accurate results, even in the presence of strong anisotropy. The results of this research are incorporated in the NORSAR seismic modelling software, and they are thus readily available for the academia and the seismic industry.
The picture illustrates the complexity of wave propagation in anisotropic media. The waves split into widely different branches, and their wavefronts shown below are all for the same travel time.