Reading the Ground's Signal: teacher key

Earthquakes, grade 7 edition, written for 7th grade. From a Chinese seismoscope to modern scales, see how people measure the shaking of the Earth and what the numbers mean.

Read the book. Print this page for the key.

Questions and answers

1. When was the earliest known earthquake detector from?
   • A.D. 132 (answer)
   • 1931
   • 1960
2. What is the difference between magnitude and intensity?
   • Intensity is the size at the source
   • Magnitude is the size at the source; intensity changes with where you stand (answer)
   • They mean the same thing
3. Why can an earthquake of magnitude 10 not happen?
   • Seismographs cannot measure it
   • Tides would stop it
   • No fault is long enough (answer)
4. Why does a deep quake shake the surface less than a shallow one of the same size?
   • Shaking drops with distance from the source (answer)
   • Deep quakes are always smaller
   • Deep rock has no waves
5. Why is ShakeAlert not prediction?
   • It only works on the Moon
   • It detects a quake that has already started (answer)
   • It guesses the year
6. In a seismograph, what does inertia keep in place?
   • The ground
   • The frame
   • The mass on a spring (answer)

Words

• seismograph: shaking recorder
• magnitude: quake size
• intensity: shaking strength
• subduction: plate sinking under
• inertia: staying put