Seismic image resolution: Numerical investigation of role of migration imaging operator

The resolution of seismic migration imaging is often given as some function of the data aperture, the size of the Fresnel zone at the image location, the frequency of the data used in the migration and the illumination of the target region. Traditional resolution analysis is based on calculation of a Point Spreading Function (PSF) in the wavenumber domain from the scattering wavenumbers at the image point. This spectral representation can be converted into a space-domain PSF by Fourier Transform. However, other issues influence image resolution or distort migrated images. For example, the velocity model is generally not reliably known and variations of the model from the true structure can have a significant impact on image focus, thus reducing resolution. Another factor that limits resolution is the type and accuracy of the propagator used in imaging. To compare the resolution of images obtained when using ray-based Kirchhoff migration with that obtained from wave equation migration, we developed a 2D heterogeneous model that can be numerically simulated. Poststack migrations of exploding reflector data obtained for the model show that the PSF are influenced by the migration operator and are not necessarily the same as expected from the range of scattering wavenumbers estimated using a simple analysis approach.