Abstract: A method of processing seismic data comprises transforming seismic data which contain coherent noise to a domain in which at least some of the coherent noise is transformed to incoherent noise. The seismic data are then filtered in the new domain, to remove or attenuate the incoherent noise. If desired, the filtered data may subsequently be transformed back to the domain in which the data were acquired. The filtering process may be carried out using a multichannel interference canceller. A seismic data trace to be filtered is input to the principal channel of the interference canceller, and one or more other seismic data traces are input to the interference canceller as reference traces. Use of seismic data traces as the reference trace(s) avoids the need to determine a noise reference trace.

Abstract: A method of determining a vertical component of particle velocity from seismic data acquired using at least one receiver disposed within a water column comprises determining the vertical component of particle velocity from the pressure at a first location and a second location. The first location is the location of a first receiver, and is vertically beneath the second location. The method uses an operator accurate for seismic data acquired at a vertical separation between the first and second locations of up to at least 0.4 times the minimum wavelength of seismic energy used to acquire the seismic data. The second location may be at or above the surface of the water column. Alternatively, the method be applied to a twin streamer seismic surveying arrangement in which the second location is below the surface of the water column and is the location of a second receiver.

Abstract: The invention concerns a method for reducing the effect of a rough sea ghost reflection in marine seismic data. According to the invention, the method comprises the steps of: providing one or a plurality of pressure sensors sensitive to frequencies below about 1 Hz;—using said sensor(s) to receive and acquire pressure data in a frequency band comprised between about 0.03 and about 1 Hz;—recording said data; and—processing said data to provide information about the sea-height above the or each sensor. The or each sensor may be a seismic sensor that can acquire seismic data substantially simultaneously with the acquisition of the pressure data in a frequency band between about 0.03 and about 1 Hz.