What is formed when P waves and S waves reach the Earth's surface?

When P waves and S waves reach the Earth's surface, they generate surface waves. Surface waves travel along the Earth's exterior rather than through its interior, distinguishing them from the primary (P) and secondary (S) waves which propagate through the Earth’s layers.

The formation of surface waves occurs due to the interaction of these seismic waves with the Earth’s surface, causing movement in the ground that can result in significant shaking during an earthquake. Surface waves generally produce more intense shaking and damage compared to P and S waves, which is why they are often the most destructive aspect of seismic events.

Understanding the formation of surface waves is crucial in the study of earthquakes and their impacts, as they can lead to large amplitude ground motion and are primarily responsible for the destruction caused in populated areas during seismic activities.