Summary Multi‐component seismic data contain richer information about the elastic parameters of the subsurface than do conventional single‐component data. Separation of the compressional and shear wavefields from multi‐component seismic data is crucial in estimating the subsurface elastic properties. We present a τ−p domain scheme to separate P‐ and SV‐wavefields from multi‐component seismic data observed at the free surface and ocean bottom. Based on plane‐wave components with known horizontal slowness in τ−p domain, the whole P‐ and SV‐wavefields are separated into the direction of observed P‐ and SV‐wave oscillations, by rotation of the horizontal and vertical components respectively. The incident P‐ and SV‐waves are extracted from the separated wavefields using plane wave partitions at the free surface and ocean bottom. The parameters used in the separation are the local seismic wave velocities and the density at the receiver location. Numerical tests on synthetic data for plane‐layered models show good performance and accuracy of the scheme.

S U M M A R YThis paper deals with theoretical aspects of wavefield decomposition of Ocean Bottom Cable (OBC) data in the τ -p domain, considering a horizontally layered medium. We present both the acoustic decomposition and elastic decomposition procedures in a simple and compatible way. Acoustic decomposition aims at estimating the primary upgoing P wavefield just above the ocean-bottom, whereas elastic decomposition aims at estimating the primary upgoing P and S wavefields just below the ocean-bottom. Specific issues due to the interference phenomena at the receiver level are considered. Our motivation is to introduce the two-step decomposition scheme called 'receiver function' (RF) decomposition that aims at determining the primary upgoing P and S wavefields (RF P and RF S , free of any water layer multiples). We show that elastic decomposition is a necessary step (acting as pre-conditioning) before applying the multiple removal step by predictive deconvolution. We show the applicability of our algorithm on a synthetic data example.

A B S T R A C TThe receiver function method was originally developed to analyse earthquake data recorded by multicomponent (3C) sensors and consists in deconvolving the horizontal component by the vertical component. The deconvolution process removes travel path effects from the source to the base of the target as well as the earthquake source signature. In addition, it provides the possibility of separating the emergent P and PS waves based on adaptive subtraction between recorded components if plane waves of constant ray parameters are considered. The resulting receiver function signal is the local PS wave's impulse response generated at impedance contrasts below the 3C receiver.We propose to adapt this technique to the wide-angle multi-component reflection acquisition geometry. We focus on the simplest case of land data reflection acquisition. Our adapted version of the receiver function approach consists in a multi-step procedure that first removes the P wavefield recorded on the horizontal component and next removes the source signature. The separation step is performed in the τ − p domain while the source designature can be achieved in either the τ − p or the t − x domain. Our technique does not require any a priori knowledge of the subsurface. The resulting receiver function is a pure PS-wave reflectivity response, which can be used for amplitude versus slowness or offset analysis. Stack of the receiver function leads to a high-quality S wave image. I N T R O D U C T I O NMulti-component seismic data contain richer information about elastic parameters of the subsurface than the conventional single-component data recorded using a streamer or a vertical component array. This is because the horizontal component data contain converted S-waves. Therefore, a joint analysis of P and S wave data provides important information on subsurface parameters such as lithology (Tatham and

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