For a controlled-source electromagnetic (CSEM) survey in a shallow water environment, the presence of the sea surface significantly hinders the interpretation of the measured data. The electromagnetic (EM) wavefields are disturbed by the sea surface. The removal of the sea-surface related wave phenomena from the data is an important step in order to robustly interpret the collected data. We propose a processing method by which the sea-surface related multiples would be removed, while a priori knowledge of the EM source wavelet becomes superfluous. The governing equations are obtained from an appropriate application of the EM reciprocity theorem that relates on one side the EM fields in the actual measurement configuration including the sea surface and on the other side the EM fields in a desired source configuration and in the absence of the sea surface, where the water layer is extended to infinity.
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