Translations:Snell's law/7/en

where i is the angle of the incident wave with a velocity V_i=V_P1 if a P-wave or V_i=V_S1 if an S-wave; $\theta _{P1}$ and $\theta _{S1}$ are the angles of reflection of the P- or S-waves in medium 1, which have velocities V_P1 and V_S1, respectively; $\theta _{P2}$ and $\theta _{S2}$ are the angles of refraction of the P- and S-waves in medium 2 which have velocities V_P2 and V_S2, respectively; p is the raypath parameter (which will be a constant along a raypath through parallel layering). If $\sin _{P2}$ or $\sin _{S2}$ exceeds 1 as given by this equation, a head wave will be generated.