Effect of Scholte wave on rotation of multi-component OBC seismic data in shallow water environment of the Arabian Gulf

Strong lateral heterogeneities of the seafloor and very shallow water depth (~10m) result in highly aliased and dispersive surface waves with complex wave polarizations in the shallow water environment of the Arabian Gulf. Compared to body waves, surface waves are characterized by low velocity, low frequency and high polarization. Well-known conventional filtering techniques are not adequate to attenuate surface waves because they take into account either velocity, frequency or polarization only. Consequently, the residual surface wave further affects the applications of subsequent processing algorithms such as geophone rotation and P/S velocity estimation. Considering the characteristics of surface waves, we in this paper present a two-step method to separate the surface waves from the reflected waves and estimate wave polarizations. This method exploits the joint relationship of wavenumber, time, frequency and polarization. First, we use a non-stationary FK filter to eliminate the effect of the surface wave from OBC record in the time-frequency-wavenumber (TFK) domain. Second, we estimate the impacts of residual Scholte waves on rotation and suppress those waves using TFK dependent polarization analysis. Analysis on field data shows that the proposed method is effective in both attenuating the surface waves and determining radial and transverse components, which results in better data for shear wave and converted wave analysis.