P- and S-waves

P-waves (primary waves) and S-waves (secondary waves) are types of seismic waves generated during an earthquake. P-waves are compressional, meaning they move by pushing and pulling the ground in the same direction as the wave travels; they are the fastest and arrive first. S-waves are shear waves that move the ground perpendicular to the wave’s direction, causing side-to-side motion; they are slower and arrive after P-waves. P-waves can travel through both solid and liquid Earth layers, while S-waves only move through solids. Studying these waves helps scientists understand Earth's internal structure.