Mapping the Hidden Plate: teacher key

Earthquakes, grade 11 edition, written for 11th grade. Nobody can see an earthquake, so seismologists reason from wave arrival times and instruments. They can place and size a quake and give its odds, but they cannot name the day.

Read the book. Print this page for the key.

Questions and answers

1. How do seismologists locate an earthquake?
   • By guessing a source and shrinking the difference from real arrival times (answer)
   • By photographing the fault from above
   • By asking people to report the date
2. At a transform boundary, what do the two plates do?
   • They slide past each other sideways (answer)
   • They push apart and make new crust
   • One sinks under the other
3. Which is early warning, not prediction?
   • Naming the date of the next quake
   • A ShakeAlert signal sent after a quake has started (answer)
   • A cloud that looks strange
4. What does Richter's scale measure?
   • The largest wiggle on a record (answer)
   • People's reports of shaking
   • How deep the ocean is
5. In this passage, what does inertia explain?
   • Why the mass on a spring stays put when the ground shakes (answer)
   • Why plates are 70 kilometers thick
   • Why tsunamis move fast

Words

• seismograph: shaking recorder
• subduction: plate sinking under
• epicenter: spot above start
• intensity: local shaking
• liquefaction: ground turning soupy
• inertia: staying put