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How to Use a Slinky to Show an Earthquake

Seismic waves, like all other kinds of waves, transmit energy. Waves can be transverse, when particles caught up in the wave oscillate at right angles to the direction the wave travels, or longitudinal, in which case particle oscillation and wave propagation are in the same direction. P waves are the fastest seismic waves from an earthquake and are longitudinal, while S waves travel somewhat slower and are transverse. Rayleigh waves travel even more slowly and are very destructive. You can use a Slinky toy to demonstrate all three kinds of waves and see how they work.

Things You'll Need

Slinky
Chair
String

Instructions

- 1
  Tie one end of the Slinky toy to a chair. Drag the other end out so the Slinky is stretched slightly.
- 2
  Pull the Slinky towards you, then rapidly push it away. You'll see a zone of compression travel the length of the Slinky. This is how a P wave affects the rocks through which it travels. All longitudinal waves behave somewhat like this.
- 3
  Shake your end of the Slinky up and down. Notice that a different kind of wave now travels along the Slinky. This is a transverse wave, and it illustrates how an S wave affects the rock through which it travels. Notice that the direction of displacement is vertical now -- perpendicular to the direction the wave travels.
- 4
  Push and pull the Slinky -- just as you did to demonstrate a P wave -- while moving it up and down. Your hand will move in a circle. The waves that travel along the Slinky now will resemble Rayleigh waves. These waves have circular motion, a little like the particles in an ocean wave. Rayleigh waves are often the most destructive seismic waves.

Nature