Tectonic hazards: Earthquakes

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  • Tectonic Hazards: Earthquakes
    • Causes
      • Caused by sudden movement within the earth
        • Could be caused along a fault line or by the upwelling of magma during a volcanic eruption.
        • The movement is the result of the release of stress in the rocks that builds up over a period of time.
          • This causes shocks or seismic waves
          • The point at which the pressure is released is called the focus.
            • This is the centre of the earthquake. The point at the earth's surface above is called the epicentre.
    • Effects
      • Ground Shaking
      • Landslides, rock and snow avalanches
        • Occur in mountainous areas when slopes are weakened by strong shaking.
      • Tsunamis
        • Seismic waves occur beneath the sea.
      • Liquefaction
        • Shock waves cause groundwater to rise to the surface turning soft ground to mud causing buildings to collapse
    • Measuring earthquakes
      • Magnitutude
        • Measured by the richter scale and given the value between the number 1 and 10
      • Intensity
        • Measures the degree of shaking of the ground and records the level of damage. Mercalli developed a 12-point scale for measuring the intensity of earthquakes which uses the observations of witnesses to the earthquake
    • What affects the amount of Damage
      • Distance away from the epicentre
      • The type of material that a building rests on.
      • The designs of buildings
    • Predictions
      • Sensitive instruments measure earth movements and the stress building up in rocks
      • Foreshocks help scientists to predict the chances of a major shock following
      • Recent earthquakes can be plotted to show if a major earthquake can be expected
    • Preparation
      • Earthquake-proof buildigs
        • Risk of fires from severed power lines and ruptured gas lines, when buildings are constructed they should  be constructed with flexible pipes.
        • Stronger buildings
      • Education
        • Government and media can provide guidance to prepare them.
      • Emergency services
        • Governments must make sure supplies are available and the emergency are prepared for a possible earthquake
        • Good communication with earthquake monitoring


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