Earthquake waves cause various effects on the rock mass through which they travel. As the waves propagate, they cause vibration in the body of the rocks through which they pass.

P-waves vibrate parallel to the direction of the wave. They exert pressure on the material in the direction of propagation. As a result, they create density differences in the material, leading to stretching and squeezing of the rock mass. These waves are similar to sound waves and can travel through gaseous, liquid and solid materials.

S-waves vibrate perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass. These waves can travel only through solid materials.

Surface waves are considered to be the most damaging waves. They move along the surface and cause displacement of rocks, leading to the collapse of structures. These waves are generated when body waves interact with the surface rocks.

The velocity of waves changes as they travel through materials with different densities. The denser the material, the higher is the velocity. Their direction also changes as they reflect or refract when coming across materials with different densities.