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Richter Scale Graphing

The Richter Scale measures the magnitude (amount of motion) of an earthquake at the focus. Unlike most scales you've used, the Richter scale is not linear. On a linear scale, the distance between each tic mark represents an equal value. The Richter scale is logarithmic. On a logarithmic scale, the distances between tic marks DO NOT represent equal values. In other words, an earthquake that registers as a nine is NOT one time larger that an eight. To help you understand this idea, you'll be making a graph that clearly shows the relationship between the Richter Scale values and actual ground motion.
 

Richter Scale Value Amplitude 100 km from Epicenter (millimeters)
2 .00004
3 .0004
4 0.004
5 0.04
6 0.4
7 4.0
8 40
9 400
  1. Study the data table on the right.
  2. Label the Richter Scale values on the x-axis. Your scale should start at 1 and end on the right at 9. Each square will represent 0.5 units.
  3. Label the amplitude values on the y-axis of your graph. Your y-axis scale should start at 0 mm and go up to 400 mm. Each square will represent 20 mm.
  4. Graph the data points and then connect the points with a single smooth line.
  5. Use the graph to help you answer the questions.

  1. Describe the shape of the curve on your graph.
     


  2. How many times GREATER is the motion experienced during a magnitude seven earthquake compared to a magnitude six? ________
  3. How many times GREATER is the motion experienced during a magnitude six earthquake compared to a magnitude five? ________
  4. How many times LESS is the motion experienced during a magnitude three earthquake compared to a magnitude four? ________
  5. On the Richter Scale, each increase in number value represents a _______ times increase in ground motion.
  6. How many times greater is the motion experienced during a magnitude nine earthquake compared to a magnitude seven? ________
  7. Estimate the magnitude for an amplitude reading of 20 mm. ________
  8. Estimate the amplitude reading for a magnitude 4.5 earthquake. ________
  9. Most people do not understand that an earthquake with a magnitude of seven is ten times greater than a magnitude six earthquake. Discuss how this might present a problem in getting people to prepare adequately for a large earthquake.
     


 

Richter Magnitude vs. Amplitude