Can You Read a Quake?

Can You Read a Quake? Name:______Class:______An earthquake has just hit. Can you tell where? You first need to know how to read a seismogram, or graphs of seismic waves.

A good seismograph can detect seismic waves from an earthquake thousands of kilometers away. In this activity, you will learn how to understand and get information from a seismogram. Questions: 1. Look carefully over the eight seismograms from the seismic stations around the world. a) Which location experienced the greatest shock? How can you tell? ______

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b) Which location is probably closest to the epicenter? How do you know?

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c) Which location is the farthest away from the epicenter? How do you know?

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2. A typical earthquake sends out at least three types of waves: Primary (P), Secondary (S), and Surface (L) waves. These waves travel differently in the earth and make different patterns on the seismogram. From the moment the first P wave arrives, the seismogram shows how many minutes pass before the S waves arrive, followed later by the L waves.

a) Which type of wave is the fastest?______

b) Which type of wave is the slowest?______

Why?______

c) At which location did the P and S waves arrive closer together – Sydney, Australia or Hawaii? What does this tell you about the location of the epicenter? ______

a) Tokyo received all three types of waves. Locate on the Tokyo seismogram the beginning of the P waves. (It would be helpful if you labeled each type of wave on the seismograms). How many minutes went by after the first P wave hit Tokyo? ______

b) How much longer did the first S wave arrive at Tokyo? ______

c) How many minutes went by until the first Surface or L wave hit Tokyo?

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3 . Name the locations that received all 3 types of waves.

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4. At some locations, not all of the three waves arrived. a) Which locations appear to have received only P and L waves, but no S waves?

b) Which locations appear to have received only L waves?

5. Some locations that are close to each other did not receive the same waves.

a) Which city, Davis-San Francisco or Los Angeles did NOT receive P waves?

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6. What are some possible explanations for why some of these cities did not receive all 3 types of waves?

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