Abstract: A technique includes receiving seismic data acquired in a seismic survey. The survey has an associated undersampled direction, and the seismic data contains samples, which are indicative of a pressure wavefield and a directional derivative of the pressure wavefield that contains information related to vertical variations. The technique includes relating the samples to the pressure wavefield or to the directional derivative of the pressure wavefield using at least one linear filter and based on the relationship, constructing a substantially unaliased continuous representation of the pressure wavefield or the directional derivative of the pressure wavefield along the undersampled direction.

Abstract: A method of processing seismic data that includes including first and second modes of seismic energy where the second mode has been generated by partial mode conversion of the first mode at a boundary face of a layer of the seabed includes the step of cross-correlating a trace acquired at a receiver and including events corresponding to the first mode with a trace acquired at the same receiver and including events corresponding to the second mode. An event in the cross-correlated data that corresponds to partial mode conversion is identified, and the amplitude of this event is normalised, for example relative to the amplitude of the peak in the cross-correlogram at zero time delay. Information about the effects of the static shift produced by the layer and/or about vector infidelity can be arrived from normalised cross-correlograms for receivers in a receiver array.