Efficient finite difference waveform modeling of selected phases using a moving zone

A new technique is presented for efficient finite difference computation and interpretational analysis of seismic wavefields. The basic idea is that the wavefield is only computed in a moving zone embracing the wave front segment under concern. Two growing challenges in seismic full wavefield modeling are addressed by this technique. Firstly, computational load may be reduced significantly without significant loss in quality. Secondly, the complexity in wavefields may be analyzed by separating into phases. Only moderate modifications are required to implement this technique in a given time-space domain finite difference code. The movement of the box which must be given prior to modeling, may be derived more or less accurately from low frequency finite difference modeling or from ray tracing. Tests in 2-D demonstrate significant reduction in memory requirements and computer time at only moderate reduction in accuracy. Extension to 3-D wavefield computation and analysis is straightforward.