Because of the elastic properties of Earth materials (rocks) and the presence of the Earth's surface, four main types of seismic waves propagate within the Earth. Compressional (P) and Shear (S) waves propagate through the Earth’s interior and are known as body waves. Love and Rayleigh waves propagate primarily at and near the Earth's surface and are called surface waves. Wave propagation and particle motion characteristics for the P, S, Rayleigh and Love waves can be demonstrated using a single slinky.
By attaching 5 slinkys to a wood block 5 people can hold the ends of the 5 slinkys (stretched out in different directions to about 3-4 m each) while one person holds the wood block. The person holding the block and can generate P or S waves (or even a combination of both) by hitting the wood block with a closed fist or causing the block to move quickly up and then down or left and then right. The purpose of this demonstration is to show that the waves propagate in all directions in the Earth from the source (not just in the direction of a single slinky).
Students will be able to:
- Describe the difference types of seismic waves including body waves (P and S) and surface waves.
- Model P-waves and S-waves with a slinky