P-waves, also known as primary waves or compressional waves, are a type of seismic wave that can travel through solids, liquids, and gases. On the other hand, S-waves, also known as secondary waves or shear waves, are another type of seismic wave that can only propagate through solids. The reason why P-waves travel faster than S-waves is due to their different modes of propagation.
P-waves are characterized by a back-and-forth motion of particles parallel to the direction of wave propagation. This motion occurs through compressions and expansions of the material. As a result, P-waves can travel through the compressible mediums of solids, liquids, and gases, allowing them to propagate faster.
On the contrary, S-waves propagate by causing particles to vibrate perpendicular to the direction of wave propagation, similar to the movement of a rope during a transverse wave. This perpendicular motion requires the material to have shear strength, which is a property found only in solid materials. Since S-waves can only travel through solids, their speed is generally slower than P-waves.
In summary, the key factors that contribute to P-waves traveling faster than S-waves are the different modes of particle motion and the ability of P-waves to travel through compressible mediums like solids, liquids, and gases, while S-waves can only propagate through solid materials.