On: “Approximating subsurface structure in areas of severe subsea erosion — A nonprocessing technique” by F. W. Lishman, and M. N. Christos (GEOPHYSICS, 54, 1397–1409, November 1989).

Two important questions were addressed in this paper. Firstly, how to construct an accurate model of a sea floor canyon — its topography and associated seismic velocities. Secondly, how the effects of such canyons can be accounted for in obtaining depths to subcanyon reflections using conventionally processed seismic data. An answer to the first question is required not only for deriving depths from conventional data but is equally required of the various canyon‐solving data processing methods listed in the paper (p. 1397). The second question is important, as the authors say, to provide a quick and inexpensive reconnaissance method of mapping structures in depth with reasonable accuracy.