Click anywhere inside the Earth to place the earthquake focus (max. depth 700 km). Space = play/pause · R = restart.

Seismic WavesRay-traced P and S waves through a layered Earth (cross-section)

Earthquake

Magnitude

Focal depth

Speed

Time

P waves (compressional) travel through solids and liquids, but slow sharply when they enter the liquid outer core and bend inward.
S waves (shear) are stopped by the liquid outer core. Together with the refracted P waves this creates the shadow zones on the far side.
Waves curve upward because speed increases with depth, and reflect off the surface (PP, SS) and the core–mantle boundary (PcP, ScS).
Slow surface waves arrive last but shake the ground the most.