The shadow zone refers to the region of the Earth from the angular distances of 104 to 140 degrees from a given earthquake, which does not get any direct P waves. The shadow zone originates from the S waves being inhibited completely by the liquid core and the P waves being refracted (bent) by the liquid core.
At almost the reverse point on the surface of the Earth, the P waves reappear. The shadow zone prevails as the waves are refracted as they pass via the boundary between the core and the mantle and are diverted from their original locations.
