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A method that extracts the response of the earth from continuous wavefields on both the source and the receiver side is presented. Seismic data recorded continuously are treated over the entire time length at once. The source(s) can emit signals continuously while moving. The entire source wavefield contributing to each stationary receiver position is derived and used to extract common receiver gathers with the response of the earth. The trace spacing in the resulting gathers can be chosen in processing and corresponding anti-aliasing protection is applied. With the proposed method, no minimum listening time is needed since both the source(s) and the receivers are operating continuously. The emitted sound pressure levels are reduced by spreading the emitted energy out in time. Multiple sources can be operated simultaneously by designing each source such that the correlation between the wavefields emitted from each of them is minimized. In a companion paper (Klüver, T., Hegna, S., and Lima J., 2018, Making the transition from discrete shot records to continuous wavefields -Real data application: Expanded abstract submitted to the EAGE annual meeting) we discuss source design using existing equipment and show application of the proposed method on real data.

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A marine seismic method based on continuous source and receiver wavefields has been developed. The method requires continuous recording of the seismic data. The source that may consist of multiple source elements can emit signals continuously while moving. The ideal source wavefield to be used with this method should be as white as possible both in a temporal and a spatial sense to avoid deep notches in the spectrum enabling a stable multi‐dimensional deconvolution. White noise has such properties. However, equipment that can generate white noise does not exist. In order to generate a continuous source wavefield that is approaching the properties of white noise using existing equipment onboard marine seismic vessels, individual air‐guns can be triggered with short randomized time intervals in a near‐continuous fashion. The main potential benefits with the method are to reduce the environmental impact of marine seismic surveys and to improve acquisition efficiency. The peak sound pressure levels are significantly reduced by triggering one air‐gun at a time compared to conventional marine seismic sources. Sound exposure levels are also reduced in most directions. Since the method is based on continuous recording of seismic data and the air‐guns are triggered based on time and not based on position, there are less vessel speed limitations compared to conventional marine seismic data acquisition. Also, because the source wavefield is spread out in time, the wavefields emitted from source elements in different cross‐line positions can be designed such that the emitted wavefield is spatially white in this direction. This means that source elements in multiple cross‐line positions can be operated simultaneously, potentially improving the cross‐line sampling and/or the acquisition efficiency.