Earthquakes create seismic waves which shake the ground as they pass. They sometimes cause buildings to topple. Earthquakes create waves just like waves of water moving across the ocean and waves of air moving across a field of wheat.

Consider what happens when a drop of rain hits a pond of water. The drop disturbs the flat surface of the water and creates waves that travel outward in all directions from the disturbance. These waves travel on the surface of the pond, along the interface between the water and the air.