A line everywhere perpendicular to wavefronts (in isotropic media). A raypath is characterized by its direction at the surface, often expressed as stepout:
where =angle with vertical, V=instantaneous velocity, and p=raypath parameter (q.v.). While seismic energy does not travel only along raypaths (i.e., seismic energy would reach points by diffraction even if the raypath were blocked), raypaths constitute a useful method of determining arrival time by ray tracing. Note that raypath bending depends on changes in velocity, not changes in acoustic impedance. Raypaths are usually shown on wavefront charts; see Figure W-3.