P Waves - Longitudinal, S Waves - Transverse
- P waves, also known as Primary Waves, are the first waves to be detected after an earthquake. They are also faster than other types of seismic waves.
- These waves are of longitudinal nature, meaning they move in the same direction as the wave is travelling. This motion is similar to the way sound waves travel.
- In solids, P waves move through by squeezing and stretching the material, while in liquids and gases they move the atoms back and forth.
If you think of it as a slinky, P waves cause the coils of the slinky to compress and expand parallel to the direction the wave is travelling.
- S waves, short for Secondary Waves, arrive at seismic stations after P waves.
- Contrary to P waves, S waves are transverse in nature, this means their motion is perpendicular to the direction of the wave travel.
- This movement causes the ground to move up and down, or side to side. This can be visualised as the movement seen when a rope is flicked up and down.
- Additionally, S waves can only move through solids. This is because liquids and gases lack the shearing strength that solids possess.
- Due to their slower speed and more destructive movement, it’s often the S waves that cause the most damage during an earthquake.
- S waves can provide critical clues to the internal structure of the Earth. Since they can’t pass through liquids, their absence in certain areas indicates that our planet’s outer core is liquid.
Mastering the properties and behaviours of P waves and S waves can help in understanding how seismic activities occur and their effects. It’s crucial in fields such as earthquake engineering and seismology.