Seismic Hazards

• Earthquake - as the crust of the earth is constantly moving, there tends to be a slow buildup of stress within the rocks. When this pressure is released, parts of the surface experience intense shaking. This is an earthquake.
• Seismic - movement of the ground: earthquakes occur at all plate boundaries​
• Retrofitting - in earthquake prone areas, buildings and other structures can be fitted with devices such as shock absorbers and cross-bracing to make them more earthquake proof.
• Tsunami - Giant sea waves generated by a shallow focus, underwater earthquakes, displacement of water, violent volcanic eruptions, underwater debris slides and landslides into the sea.
• Epicentre - the point immediately above the focus on the earth's surface​
• Focus - the point where the pressure release occurs within the crust: where the earthquake originates
• Magnitude - size of an earthquake using amplitude or seismic waves
• Richter scale - a logarithmic scale proportional to the magnitude
• Mercalli scale - measures the intensity of an event and its impact using a 12 point scale
• MMS (Moment Magnitude Scale) - energy released
• Landslides and avalanches - slope failure as a result of ground shaking
• Liquefaction - when violently shaken, soils with a high-water content lose their mechanical strength and behave like a fluid - collapses buildings and infrastructure
• • P waves can travel through liquid and solids and gases, while S waves only travel through solids​
  • S waves are the most destructive – leads to the collapse of buildings
• Tsunamis:​

  • P waves uplift / displace​
  • Water above the earthquake is displaced vertically, causing the sea to lift and generate waves that gain height as the water shallow.​
  • Can reach up to 600m inland​
  • Generated by a shallow focus​
  • Drawdown – reduction in sea level (first warning)​
  • Destructive plate boundaries