Earthquake waves

Earthquake waves are the vibrations sent out through the ground by earthquakes. They are also called seismic waves. They are two kinds of deep earthquake wave: primary (P) waves and secondary (S) waves.

• P waves travel at 5 km per second and move by alternately squeezing and streching rock.
• S waves travel at 3 km per second and move the ground up and down or from side to side.

There are two kinds of surface wave: Love waves and Rayleigh waves.

• Love, or Q, waves shake the ground from side to side in a jerky movement that can often destroy very tall buildings.
• Rayleigh, or R, waves shake the ground up and down, often making it seem to roll.

In solid ground earthquake waves travel too fast to be seen. However, they can turn loose sediments into a fluid-like material so that earthquake waves can be seen rippling across the ground like waves in the sea.