1. A method comprising: obtaining, by a computer system, a seismic data volume; identifying, by the computer system, a plurality of patches in the seismic data volume, and the identifying thereby creating a patch volume, the patch volume distinct from the seismic data volume; and then displaying, on a display device, at least a portion of the seismic data volume, and simultaneously displaying on a display device the plurality of patches of the patch volume; assigning a patch of the plurality of patches to a subsurface horizon of the seismic data volume by selecting from a display device a first patch of the patch volume and designating the first patch to be a portion of a first subsurface horizon; and discarding a patch from the patch volume by selecting from a display device a second patch of the patch volume, identifying the second patch as not belonging to a subsurface horizon, and removing the second patch from the patch volume.