Multi-component wavefield decomposition versus PZ summation: A comparative study
Sanyu Ye · 2011
The elastic wave equation based multi-component (MC) wavefield decomposition (WFD) was proposed during 90s, only few years later from the PZ summation. Theoretically the WFD can be regarded as a MC summation in tau-p domain, while the PZ summation a special case of WFD for acoustic two component at vertical incidence, thus can be performed in x-t domain. While the PZ summation requires only the proper matching between P (hydrophone) and Z component, the WFD in addition needs not only knowledge about the seabed elastic properties at the immediate vicinity of receiver but also the transform into tau-p domain. The estimation of seabed elastic properties may seem theoretically simple but in practice a daunting if not impossible task due to poor coupling, amplitude saturation/clipping, overscaling and source directivity. The tau-p transform for field data is very challenging due to irregular and sparse sampling (shot) interval that requires regularization and trace interpolation. Because of the aliased nature of field data, the regularization and trace interpolation lead inevitably to smearing and loss of data. All these complexity and difficulty related to WFD may explain why the PZ summation have been established as standard procedure for OBC (Ocean Bottom Cable) data, while WFD remains yet in the shadow despite its theoretical superiorities like complete elimination of water bottom multiple of direct water waves, receiver side multiples from deep reflections, clean separation of upgoing S waves etc.