Science Olympiad Dynamic Planet Practice Test

Which type of seismic wave travels faster, P waves or S waves?

1. P waves

2. S waves

3. Both travel at the same speed

4. Surface waves

The correct answer is: P waves

P waves, or primary waves, are seismic waves that travel faster than S waves, or secondary waves. This is primarily because P waves are compressional waves that propagate through materials by compressing and expanding them in the direction of the wave’s travel. These waves can travel through both solids and liquids, which allows them to move rapidly through the Earth's interior. In contrast, S waves are shear waves that move the ground perpendicular to the direction of the wave's travel. They can only move through solids, which limits their speed compared to P waves. The differences in wave types and their propagation mechanisms account for the observed speed disparity. This fundamental difference in properties explains why P waves are the first to be detected by seismographs after an earthquake, reflecting their faster speed. In geological studies and earthquake analysis, understanding the speed of these waves is crucial for interpreting seismic data and assessing the internal structure of the Earth.