Why multiples do not contribute to deconvolution imaging

The question whether multiples are signal or noise is subject of ongoing debate. In this paper we consider correlation and deconvolution imaging methods and analyse to what extent multiples contribute to the image in these methods. Our starting point is the assumption that at a specific depth level the full downgoing and upgoing fields (both including all multiples) are available. First we show that by cross correlating the full downgoing and upgoing wave fields, primaries and multiples contribute to the image. This image is not true-amplitude and is contaminated by cross-talk artefacts. Next we show that by deconvolving the full upgoing field by the full downgoing field, multiples do not contribute to the image. We use minimum-phase arguments to explain this somewhat counterintuitive conclusion. The deconvolution image is true-amplitude and not contaminated by cross-talk artefacts. The conclusion that multiples do not contribute to the image applies to the type of deconvolution imaging analysed in this paper, but should not be extrapolated to other imaging methods. On the contrary, much research is dedicated to using multiples for imaging, for example in full wavefield migration, resonant migration and Marchenko imaging.