Objective: To understand the difference in travel times of P and S waves during an earthquake and to know how to use this time difference to calculate epicenter distance.
Standards: Structure of Earth System (layering and properties of Earth’s internal structure; plate tectonics and its relation to earthquakes), Transfer of Energy (energy types, characteristics, and transfer properties), and Interactions of Energy and Matter (waves have energy and can transfer energy when they interact with matter).
Materials: Three pieces of paper, marker or pen, and a measuring tape.
(1) Make three signs with different city names on them.
(2) Hang these signs in the hallway at different distances from the end of the hall before class.
(3) Designate one student the earthquake epicenter, one student the P wave, and another student an S wave.
(4) The P and S wave stand together at the epicenter. When you sound “earthquake!” the P wave begins running while the S wave begins walking.
(5) When the P wave reaches the first city, both waves stop.
(6) The remaining students measure the distance between the P and S waves. Briefly discuss why there is a difference.
(7) The P and S waves go back to the epicenter and the procedure is repeated two more times, as the P wave stops at the second city and then the third city.
*** This demo should be done in an area that will not interrupt other classes***
Science Behind It: P and S waves travel at different speeds because they contain different amounts of energy. The two waves also travel at different rates because P waves can easily travel through both solid and liquid material, whereas S waves can only travel through solid materials. Knowing the properties of these waves and how to calculate their travel times and distances, is integral in seismologists pinpointing the location of an earthquake’s epicenter. Through completing this kinesthetic demonstration, students will have an insight and understanding of this process.