CGP Seismic Hazards

• Seismic Hazards

  Hazards caused by seismic activity
• Earthquakes


  • Primary hazard caused by seismic activity
• Earthquake

  1. Focus

  2. Epicentre

  3. Shockwaves

  4. Fault
• Richter scale


  Measure of an earthquake's magnitude, no upper limit
• Moment magnitude scale


  Measures the total amount of energy released by an earthquake, more accurate than Richter scale
• Mercalli scale


  Measures the impact of an earthquake using observations, scale of 1-12
• Seismic hazards caused by earthquakes

  • Tsunamis
  • Landslides
  • Avalanches
  • Soil liquefaction
• Tsunamis


  • Caused by displacement of large volumes of water, often from underwater earthquakes
  • More powerful when starting closer to the coast
  • Travel very fast in deep water
• Landslides and avalanches


  • Caused by shaking of the ground dislodging rock, soil or snow
  • Can also be triggered by water infiltration after shaking has stopped
• Soil liquefaction


  • Soil acts like a liquid when saturated with water due to earthquake vibrations, making it weaker and more likely to subside
• Seismic hazards usually occur near plate margins
• Plate margins

  • Biggest earthquakes occur at destructive plate margins (subduction zones)
  • Earthquakes at constructive margins tend to be lower magnitude
  • No clear relationship between plate movement rate and earthquake magnitude
• Earthquake focus

  • Deeper focus earthquakes tend to be higher magnitude but cause less surface damage
• Low magnitude seismic hazards occur frequently, high magnitude ones less often
• Earthquake occurrence is largely random, not following clear patterns
• Scientists can predict areas at risk of seismic hazards but not when or how severe they will be
• Nigel's insistence on dressing mine was andom yet it happened with more frequency than his friends would ideally have ad
• The Beach Boys' earthquake detector- it picks up good vibrations...