The Odds Under Our Feet: teacher key

Earthquakes, grade 12 edition, written for 12th grade and up. Earthquakes cannot be seen or scheduled, yet scientists work out where they start, how big they are and how likely the next one is. The evidence shows what they can know and where it runs out.

Read the book. Print this page for the key.

Questions and answers

1. How many earthquakes of magnitude 6 or larger struck the San Francisco Bay area from 1979 to 1989?
   • Four (answer)
   • None
   • One
2. What must a real earthquake prediction give?
   • Date and time, location, and magnitude (answer)
   • Only the magnitude
   • Only the place
3. Why can ShakeAlert warn people before the strongest shaking?
   • It can stop a fault from slipping
   • It predicts quakes a year ahead
   • P-waves outrun the damaging waves and data outrun both (answer)
4. Which statement about magnitude 10 is true?
   • It happens about once a year
   • It cannot happen, because no fault is long enough (answer)
   • It has been recorded in Chile
5. In this passage, what do precursors mean?
   • Early signs such as small-quake swarms or radon (answer)
   • A kind of fault
   • A very fast wave

Words

• subduction: plate sinking under
• intensity: local shaking
• liquefaction: ground turning soupy
• precursors: early signs
• epicenter: spot above start