The Energy of Earthquakes

• Introduction
• What you need for this project
• Activity: Calculate the Energy released by Earthquakes
• Examples of Energy Released by Other Events

Introduction

Earthquake data can be incorporated into a curriculum unit on energy. Scientists have found that the seismic released during an earthquake is related its surface wave magnitude (M_s) according to the equation:

E= 1.74 x 10^{(5 + 1.44M_s)} joules.

The unit of energy is joule, abbreviated J. Joule is the SI unit of work and energy equal to the work done by a force of one newton, when its point of application moves one meter in the direction of the force.

The PEPP Learning Library has more information on earthquake magnitudes and how they are calculated. You can also find information on how to calculate energy released by earthquakes in the PEPP (NZ version) curriculum project Earthquake Magnitudes.

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What you need for this project

To show the relationship between energy and earthquake magnitudes you will need:

• PEPP MAPPER software or recordings of earthquakes with surface wave magnitudes available
• Hand or computer calculators
• Graph paper or graphing software.

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Activity: Calculate the Energy released by Earthquakes

1. Use the PEPP MAPPER software and the Hypocenter Catalog to find a series of earthquakes with different surface wave magnitudes. Similarly, look at your own collection of recorded earthquakes and note the surface wave magnitudes.

2. As a whole class or working in small groups or individually, have students calculate the energy released by each of these earthquakes using the above equations.

3. Using their energy calculations for the earthquake data set, have students create graphs of magnitude vs. seismic energy released to give a general picture of the relationship between magnitude and seismic energy.

4. From their graphs, can they estimate how much more energy is released by a magnitude 6 earthquake than by a magnitude 5 earthquake? Approximately how much energy would be released by a magnitude 10 earthquake?

For every 1 point increase in magnitude, students will find that the amount of seismic energy released increases by a factor of 27.6.

5. Students may want to compare the energy released by earthquakes to other sources of energy and plot these values on their graphs. Below are some examples. Textbooks, reference books, and the Internet will have other examples. Often energy units will be expressed in ergs (1 joule = 10⁷ ergs) or other units so your students may need to do some conversions in order to compare these events to earthquakes.

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Examples of Energy Released by Other Events

The energy released by the atomic bomb dropped on Bikini Island in 1946 was about 10¹² joules.

Each year the consumption of energy in the United States is about 10¹⁹ joules.

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