Prediction or Prevention?

1995 The Regents of the University of California
To do this activity...
The main lesson outline will help you understand the questions in this activity. However, you do not need to have done the other activities.

Congratulations! You have just joined a team of geologists assigned to predict or prevent earthquakes. This is a challenging job! Read through the following two descriptions to determine which team you are joining. Prepare to write answers to the issues for each team and to discuss your answers with classmates. (Your instructor may assign you one or both teams.)

Prediction Team:

You are on a geologic team with the task of predicting earthquakes. Your team has a new prediction method that has never been tested before, but you believe it will predict some earthquakes larger than magnitude 5.0 on the Richter scale.

One day at work, your instruments tell you that there is a 3% chance of a 7.2-magnitude earthquake in San Fransisco within the next 15 minutes. What should you do? Answer these questions:

a) What emergency preparations would you recommend to the people and businesses of San Francisco in the next 15 minutes?

b) If you send an emergency warning, will it save lives? How many might be saved?

c) If the mass population panics, could the panic itself cause deaths even without a quake? Would it cause major economic problems (e.g. loss of business, congestion of freeways, overloading of telephone lines, etc.)?

d) Which situation would be worse: (1) You send a warning to San Francisco but the quake does not occur; or (2) you do NOT send a warning and the quake does occur? Explain your reasons.

Prevention Team:

Your team has been developing a method to prevent large earthquakes from occurring. After much research your team has made five important conclusions:

1. An earthquake fault in your local area has built up enough strain to cause a major earthquake of magnitude 6.0 or larger.

2. There is a 50% chance that this major earthquake will strike within the next 10 years.

3 You may be able to prevent this single large quake by causing a series of about 25 small quakes in the same location to release the strain in the rocks.

4. You predict that each of these small quakes will be less than 5 on the Richter scale.

5. There is a 10% chance that the series of small quakes would actually trigger the major quake instead of preventing it.

Now here are the questions you must answer:

a) How much damage would be caused by 25 quakes measuring 5.0? Is this better or worse than one quake measuring 6.0? Who would benefit more from the 25 smaller quakes? Who would be more seriously affected by 25 small quakes?

b) Considering the risk of setting off the major quake, should you attempt the 25 smaller quakes? Why or why not? If a major quake does occur, can you be held responsible? If you do not attempt to prevent the larger quake and it actually does occur, can you be held responsible, since you had a method to prevent it?

Follow-Up Research:

What different methods have people used in the past and in recent years to predict earthquakes? Describe each method and the people that used it. How successful was each method? How scientific was the method? Here are some examples to research:

a) Unusual animal behavior
b) Radon gas
c) Location of planets and other astronomical objects
d) Electromagnetic or sound waves emitted from the ground
e) Measurement of ground movement near a fault line

Return to the main lesson ("Earthquake!").
Mail comments to

All text, images, and other resources in this page are Copyright 1995, The Regents of the University of California. All rights reserved. For permission, email

Return to the CEA Science Education Home Page