Body Waves
Seismic waves are classified into two basic categories: body waves and surface waves. Body waves travel through the interior of the Earth and surface waves travel across the Earth's surface.
Body waves can be further classified as either primary (P) waves or secondary (S) waves. P waves are compressional waves, which means that they cause particles of the Earth to vibrate back and forth in the same direction as the wave is traveling. P waves are the fastest of the seismic waves and can travel through all types of material, including solids, liquids, and gases.
S waves are shear waves, which means that they cause particles of the Earth to vibrate from side to side, perpendicular to the direction the wave is traveling. S waves can only travel through solids.
Surface Waves
Surface waves are generated when body waves reach the Earth's surface. The most common types of surface waves are Love waves and Rayleigh waves.
Love waves are similar to S waves, but they travel along the surface of the Earth instead of through the interior. Rayleigh waves are a combination of P waves and S waves that move in an elliptical motion along the Earth's surface.
