Seismic Waves

Name: _________________________________       Date: _____________

When an earthquake strikes, different kinds of waves race through the Earth from the quake's epicenter. What are the different kinds of seismic waves and how do they move? Which waves are the most destructive? How are they detected and measured? You'll find out with this activity.

1. To begin, read about Seismic Waves. What are seismic waves?
   
   
   
   
2. Describe the difference between body waves and surface waves. Which are more damaging?
   
   
   
   
3. What's the difference between primary and secondary waves?
   
   
   
   
4. Click Play for the Seismic Wave animation (below the descriptions of primary and secondary waves). Describe the difference between the way S and P waves move through the ground.
   
   
   
   
5. Based on the animation, what's the difference between an earthquake's focus and its epicenter?
   
   
   
   
6. Describe how surface waves move across the surface during an earthquake.
   
   
   
   
7. Explain why surface waves are so damaging.
   
   
   
   
8. Next, you'll explore how seismic waves are used for finding an earthquake's origin. What does the exact speed of P and S waves depend on?
   
   
   
   
9. What is the ratio of P to S wave speed?
   
   
   
   
10. Go to the USGS Science of Earthquakes page and scroll to How Are Earthquakes Recorded? How do seismographs work?
    
    
    
    
11. How do scientists measure the size of an earthquake?
    
    
    
    
12. How can scientists tell where an earthquake happened using P and S waves?
    
    
    
    
13. Describe how triangulation works.
    
    
    
    
14. Based on what you've learned about P and S waves, what can you conclude about their relative speeds?