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Chapter 2   Earthquakes

Chapter 2 Earthquakes






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    Chapter 2   Earthquakes Chapter 2 Earthquakes Presentation Transcript

    • The Changing Earth Chapter 2: Earthquakes
    • Section 2.1 Earthquakes Occur Along Faults
    • Continued – See page 46
    • 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.
    • 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.
    • 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.
    • 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.
    • Section 2.2 Earthquakes Release Energy
    • 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.
    • Continued – See page 52
    • 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.
    • 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.
    • Continued – See page 55 All waves, including seismic waves, carry energy from place to place.
    • Continued – See page 56 Seismographs record ground movement.
    • Continued – See page 57 Scientists use seismograph information to locate the epicenter of an earthquake.
    • Section 2.3 Earthquake Damage Can Be Reduced
    • 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.
    • Continued – See page 51
    • 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.
    • 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.
    • Continued – See page 65
    • 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