I do not fully understand the physical mechanism of formation of Rayleigh waves at the free surface. While their derivation is quite clear and obey free-boundary conditions, it is not clear their physical mechanism.
Could you please correct me in my discussion. Incident P-wave can transform to reflected P and SV waves. When the angle of incidence of P wave reaches 2nd critical angle, both outgoing P and SV waves propagate along the surface forming Rayleigh wave. So, P-wave by itself can form Rayleigh wave. At the same time, incident SV wave can transform to reflected P and SV waves. When the angle of incidence of SV wave (again) reaches second critical angle - both outgoing P and SV waves propagate along the surface forming Rayleigh wave.
Can then Rayleigh wave be formed by interference of both incident P and SV waves on the free surface or Rayleigh waves are formed only separately by incident P or SV waves? Does it mean that right under the epicenter Rayleigh waves cannot form but at some distance from it in order to reach second critical angles?