Tomographic imaging by reflected and refracted arrivals at the North Sea

We discuss some processing steps of a marine 3-D data set from the Oseberg field, North Sea. We compare the prestack depth-migrated images obtained by the velocity fields provided by different tools: velocity spectra, reflect ion tomography, and joint tomographic inversion of reflected and refracted arrivals. The last ones are definitely better. We also produced a synthetic example by modeling the estimated earth structure and the actual recording geometry, and we reached similar conclusions. The correlation between reflected and refracted signals may be unclear for later arrivals because of their reciprocal interference and multiple reflec tions. We adopt a technique based on a surgical mute in the tau-p domain. w hich allows coupling the signals coming from the same elastic interface.