Dictionary:Diodic

(dī’ ∂d ik)
1. Behaving differently in different directions, i.e., like a diode.
2. Diodic velocities occur for C-waves if $ V_{P} $ and/or $ V_{S} $ vary laterally. Hence, the traveltimes of common-conversion point C-waves change if shot in opposite directions (unless also changing P-source to S, and S-receiver to P). Such C-waves obey the Vector Reciprocity Theorem, not the Scalar Reciprocity Theorem, as with pure P-modes.