Exploring Seismic Waves with Slinkys

30min Novice

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

Related Animations

Seismic shadow zones have taught us much about the inside of the earth. This shows how P waves travel through solids and liquids, but S waves are stopped by the liquid outer core.

Animation Novice

The wave properties of light are used as an analogy to help us understand seismic-wave behavior.

Animation Novice

The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The different phases show how the initial P wave changes when encountering boundaries in the Earth.

Animation Novice

The shadow zone results from S waves being stopped entirely by the liquid core. Three different S-wave phases show how the initial S wave is stopped (damped), or how it changes when encountering boundaries in the Earth. 

Animation Novice

Seismic waves travel at different speeds through different materials. In this 2-layer model two wave fronts leave an impact at the same time but the lower layer is faster. 

Animation Novice

Seismic waves travel a curving path through the earth due to changes in composition, pressure, and temperature within the layers of the Earth. 

Animation Novice

Animation shows the race between the direct seismic wave vs. the deeper, longer-path critically refracted seismic wave. Graph records the arrival times.

Animation Novice

In this model of increasing velocity with depth, the critically refracted seismic rays speed up with depth as they pass 5 different velocity boundaries.

Animation Intermediate

Related Videos

A video demonstration of how a slinky can be a good model for illustrating P & S seismic waves movement.

Video Novice

Video lecture on wave propagation and speeds of three fundamental kinds of seismic waves.

Video Novice

Related Lessons

Working in both small groups and as a whole class, students investigate the classic Earth science analogy: "Seismic waves radiate outward from an earthquake's epicenter like ripples on water". A discrepant image connects the unfamiliar concept of the spreading out of seismic waves to the more familiar scenario of ripples on water radiating outwards in all directions after a droplet falls onto a pool. 

Lesson Novice

Related Fact-Sheets

Earthquakes create seismic waves that travel through the Earth. By analyzing these seismic waves, seismologists can explore the Earth's deep interior. This fact sheet uses data from the 1994 magnitude 6.9 earthquake near Northridge, California to illustrate both this process and Earth's interior structure.

NOTE: Out of Stock; self-printing only.

Fact-Sheet Novice

Related Posters

This poster combines a visualization of ground motion resulting from the February 21, 2008 M 6.0 earthquake that occurred near Wells, NV, with the image of a faucet to illustrate a classic Earth science functional analogy: "Seismic waves radiate outward from an earthquake's epicenter like ripples on water".

Poster Novice

Seismic waves from earthquakes ricochet throughout Earth's interior and are recorded at geophysical observatories around the world. The paths of some of those seismic waves and the ground motion that they caused are used by seismologists to illuminate Earth's deep interior.

Poster Intermediate

Related Software-Web-Apps

An interactive website, where one can investigate the classic Earth science analogy; "Seismic waves radiate outward from an earthquake's epicenter like ripples on water". 

Software-Web-App Novice

jAmaSeis is a free, java-based program that allows users to obtain and display seismic data in real-time from either a local instrument or from remote stations.

Software-Web-App Novice

We encourage the reuse and dissemination of the material on this site as long as attribution is retained. To this end the material on this site, unless otherwise noted, is offered under Creative Commons Attribution (CC BY 4.0) license