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Chapter 2   Earthquakes
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Chapter 2 Earthquakes


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  • 1. The Changing Earth Chapter 2: Earthquakes
  • 2. Section 2.1 Earthquakes Occur Along Faults
  • 3. Continued – See page 46
  • 4. Rocks move along faults.
    • The lithosphere contains huge breaks (faults) where movement of rock occurs.
    • Movement can be slow or fast, or may stop if the two sides lock together.
    • The pressure of the rocks causes stress to build up.
    • T h e stored energy is released and causes an earthquake – sudden ground motion.
  • 5. Faults are classified by how rocks move.
    • Normal Fault: a block of rock above the fault plane moves down relative to the other block. Caused by two rocks pulling apart.
  • 6. Continued – See page 48
    • Reverse Fault: the block above the fault plane moves up relative to the other block. Caused by the two blocks of rock being pushed together.
  • 7. Continued – See page 49
    • Strike-slip Fault: the blocks of rock move horizontally on either side of the fault plane. Caused by rocks being pushed horizontally.
  • 8. Section 2.2 Earthquakes Release Energy
  • 9. Energy from earthquakes travels through Earth.
    • Focus: underground location where earthquake begins.
      • The crust breaks at the focus.
      • Released energy radiates outward in ALL directions.
      • Energy is in the form of seismic waves.
    • Epicenter: the point on the Earth’s surface directly above the focus.
  • 10. Continued – See page 52
  • 11. Continued
    • Three types of seismic waves:
      • Primary: travel the fastest and therefore arrive first at any location. They can travel through any material.
      • Secondary: travel more slowly than primary waves and arrive second. They do not travel through liquids or gases.
      • Surface: travel along the surface of the crust and cause the most damage. They arrive last.
  • 12. Seismic waves can be measured.
    • Seismograph: instrument used to detect and record ground movements.
      • The shaking is recorded on paper or magnetic tape.
      • Some record horizontal movement and others record vertical movement.
    • Seismograms from three different locations are needed to locate the epicenter.
      • The difference in arrival times of the P and S waves are used to calculate it.
  • 13. Continued – See page 55 All waves, including seismic waves, carry energy from place to place.
  • 14. Continued – See page 56 Seismographs record ground movement.
  • 15. Continued – See page 57 Scientists use seismograph information to locate the epicenter of an earthquake.
  • 16. Section 2.3 Earthquake Damage Can Be Reduced
  • 17. Earthquakes can cause severe damage and loss of life.
    • The Moment Magnitude Scale, and The Richter Scale, are used to measure magnitude.
    • Loss of life, structural damage, fires, landslides, and sinking of structures due to liquefaction (soil acting like a liquid) can be devastating.
    • Aftershocks, weaker earthquakes, often follow.
    • Earthquakes can trigger tsunamis which travel quickly as a series of waves.
  • 18. Continued – See page 51
  • 19. Some scientists work to monitor and predict earthquakes.
    • Predictors include:
      • Changes in elevation of the ground.
      • Slow movement of blocks of rock.
      • Formation of small cracks in the ground.
    • Seismic Gap: area along an active fault where no quakes have occurred for a long time.
      • May indicate stress is building up.
  • 20. Continued – See page 64 Scientists cannot yet predict the day or even year when an earthquake will occur, but they can make long term predictions.
  • 21. Continued – See page 65
  • 22. Structures can be designed to resist earthquake damage.
    • Strict building codes are enforced in active earthquake regions.
      • Steel reinforced shear walls
      • Fastened to foundation
      • Isolators between the building and foundation.
      • Cross braces