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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.

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 