## Seismic Slinky: Modeling P and S waves

p.p1 {margin: 0.0px 0.0px 6.0px 0.0px; line-height: 14.0px; font: 11.0px 'Myriad Pro'} span.s1 {font-kerning: none} span.s2 {text-decoration: underline ; font-kerning: none; color: #005ede}

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.
P waves travel at over 360 km/hr (225 mi/hr) 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.

#### Objectives:

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

• 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

Level: Novice

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Video Novice

## Related Animations

Seismic waves travel through the earth to a single seismic station. Scale and movement of the seismic station are greatly exaggerated to depict the relative motion recorded by the seismogram as P, S, and surface waves arrive.

Animation Novice

We use exaggerated motion of a building (seismic station) to show how the ground moves during an earthquake, and why it is important to measure seismic waves using 3 components: vertical, N-S, and E-W. Before showing an actual distant earthquake, we break down the three axes of movement to clarify the 3 seismograms.

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

## Related Lessons

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.

Lesson Novice