|Wave Equation Migrations, which include Phase Shift (WEM) and Reverse Time Migrations (RTM), address the multi-arrival problems that plague many ray-based Kirchhoff migrations, and provide more accurate images of the subsurface. In addition to resolving wave phenomena associated with complex velocity structures, Wave Equation migrations naturally incorporate the full aperture, providing operational advantages over Kirchhoff migrations when performing full volume imaging. In addition, because the migrations are wave equation-based rather than ray-based, they generally produce images with less background or operator noise than those created with Kirchhoff migrations.|
The WEM of Phase Shift type is based on downward continuation of the wavefield, using a one-way wave equation solution. The Reverse Time Migration uses a two-way wave equation solution.
WEM is faster than RTM, and is suitable for imaging in complex areas. However, it is not recommended for imaging very steep dips, and it doesn't account for turning waves, like RTM does.