Seismic Slinky: Modeling P and S waves


Students will produce P and S waves using a Slinky© to understand how seismic waves transfer energy as they travel through solids. All types of waves transmit energy, including beach waves, sound, light, and more. When an earthquake occurs it generates four different types of seismic waves).  We will focus on two of these:  Compressional-P (longitudinal) and shearing-S (transverse) “body waves.”  These travel through the Earth with distinct particle motion and predictable speed. 
Near the surface P waves travel at ~6km/s, that is 21,600 km/h, which is something like 13,400 miles per hour through solid rock, compressing and dilating the Earth in the direction they are propagating, much like sound waves do. They also travel 60% faster than the shearing S waves. It is this velocity difference that helps seismologists locate an earthquake’s epicenter.


By the end of the exercise, students should be able to:

  • produce both P and S waves using a Slinky© 
  • use the model as a tool to observe and understand wave properties
  • describe the difference between P  and S seimic waves based on the direction of particle motion relative to the direction of propagation
A video demonstration of how a slinky can be a good model for illustrating P & S seismic waves movement.
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A video demonstration of how a slinky can be a good model for illustrating P & S seismic waves movement.

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The slinky is an effective tool for the demonstration seismic wave characteristics and wave propagation. Slinkys can be used both individually and in various combinations to demonstration different concepts.

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