P063 Analysis of Guided Waves Recorded on Permanent Ocean Bottom Cables P.J. Hatchell* (Shell International Exploration & Production BV) P.B. Wills (Shell International Exploration & Production BV) & M. Landro (NTNU) SUMMARY Guided waves propagating in the water layer are observed on data from the permanent OBC cables at Valhall. These waves have large amplitudes and result from post-critical p-wave reflections at the seafloor. Two methods for analyzing these waves are examined: one in terms of the normal mode theory of Press and Ewing and the second in terms of ray theory. It is found that the dispersion relationship predicted