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Recorder: How Does a Seismograph Record the Magnitude of an Earthquake? (page 2)

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Author: Janice VanCleave

Let's Explore

  1. Does the weight of the cup affect the seismogram produced? Repeat the experiment, using an empty cup.
  2. Does the direction of the earthquake affect the pattern on the seismogram? Use a compass to position the box so that the tape points in a north-to-south direction. Repeat the experiment, shaking the box from the four different di:ections: north (back), south (front), east (nght side), and west (left side). Science Fair Hint: Use the model as part of a project display. Label each seismogram with the direction of the vibrations.

Show Time!

Construct a sensitive seismograph using a beam of light. Place a bowl full of water on a table. Ask a helper to hold a flashlight so that its beam of light falls on the surface of the water and is reflected to a nearby wall. Watch the spot of light on the wall while you gently tap the surface of the water with your finger. Produce other small quakes by tapping the bowl or the table.


Check it Out!

Andrija Mohorovicic (1857–1936), a Yugoslavian seismologist, analyzed the seismograms of a Balkan earthquake in 1909. Read about this scientist, and think about these questions:

  • What did Mohorovicic discover from the seismograms about the speed of seismic waves at depths around 25 miles (40 km)?
  • What is Moho short for?
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