Removal of water-layer multiples from multicomponent sea-bottom data

A method for suppressing water-layer multiples in multicomponent sea-floor measurements is presented. The multiple suppression technique utilizes the concept of wavefield separation into upgoing and downgoing modes just below the sea floor for eliminating the seafloor ghost, the sea-surface ghost, a nd the accompanying water-layer reverberations. The theory applies to each of the recorded components: pressure, vertical velocity, and horizontal vel ocities. The fundamental physical principle for the multiple suppression te chnique rests on identifying these multiples as downgoing waves just below the sea floor, while the primaries of interest arriving from the subsurface are upgoing waves. White presented this realization for the pressure compo nent three decades ago; hence, the theory for the velocity field is an exte nsion of the theory. in this paper, the theory is derived for an experiment with a marine source in the water layer above a locally Flat, elastic sea floor with known elas tic parameters. The method is otherwise multidimensional and operates on a shot-to-shot basis; hence, it is computationally fast. Aside from this, we show that this demultiple method removes the strongest multiples in sea-flo or data without knowledge of the source wavelet. Synthetic and real data examples are provided to illustrate the application of the algorithms to the pressure, in-line velocity, and vertical velocity components. The numerical tests show that strong multiples have been atten uated on the pressure and the velocity recordings, producing promising resu lts.