Fig. 1. (Color online) (a) The P-wave shadow zones as well as the core structure of the Earth [Adapted from Ref.
1, (b) The P-wave propagation model inside the Earth implemented with `Ray Optics Simulation'. The asterisk indicates the light source, the shadow region is indicated by a red arrow, and the P waves inside the shadow region are reflected from the boundary of the inner core and are indicated by a blue arrow. Faint lines in the background represent light paths created by continuous reflections [Adapted from Ref.
4].
