The study of seismic waves has improved our understanding of Earth's interior. In general, the velocities of P and S waves indicate the rigidity or stiffness of the material. Faster P and S waves indicate greater rigidity (strength).
Further, S waves cannot travel through liquids because they lack rigidity. Does the velocity of P waves and S waves increase or decrease immediately below the lithosphere? The velocity of P waves and S waves ____ immediately below the lithosphere.