The two main types of seismic waves are P-waves and S-waves. P-waves, also known as primary waves, are the fastest seismic waves and can travel through solids, liquids, and gases. They cause particles to move in the same direction as the wave is traveling. On the other hand, S-waves, or secondary waves, are slower than P-waves and can only travel through solids. They cause particles to move perpendicular to the direction of the wave.
