A consequence of a buried focus such as can be produced by sharp synclinal curvature or focusing by a velocity lens. For zero offset and constant velocity, this occurs where the radius of curvature for a concave-upward reflector is less than the reflector depth. See Figure B-11 and buried focus. The reverse branch involves a phase shift; see Sheriff and Geldart (1995, 156). Compare backward branch. Also called retrograde branch.