SEISMIC MIGRATION AND ABSORBING BOUNDARIES WITH A ONE-WAY WAVE SYSTEMFOR HETEROGENEOUS MEDIA

A first-order one-way wave system has been created based on characteri stic analysis of the acoustic wave system and optimization of the disp ersion relation. We demonstrate that this system is equivalent to a th ird-order scalar partial-differential equation which, for a homogeneou s medium, reduces to a form similar to the 45 degrees paraxial wave eq uation. This system describes accurately waves propagating in a 2D het erogeneous medium at angles up to 75 degrees. The one-way wave system representing downgoing waves is used for a modified reverse time migra tion method. As a wavefield extrapolator in migration, the downgoing w ave system propagates the reflection events backwards to their reflect ors without scattering at the discontinuities in the velocity model. H ence, images with amplitudes proportional to reflectivity can be obtai ned from this migration technique. We present examples of the applicat ion of the new migration method to synthetic seismic data where P-P re flections P-SV converted waves are present. Absorbing boundaries, usef ul in the generation of synthetic seismograms, have been constructed b y using the one-way wave system. These boundaries absorb effectively w aves impinging over a wide range of angles of incidence.