Earthquakes

• Earthquakes cannot be predicted, and occur when there is a sudden release of energy, underground, as tectonic plates try to push past each other along fractures
• Earthquake occurrence


  1. Built up pressure is suddenly released

  2. Sending out pulses of energy
• Focus


  The origin of the earthquake
• Epicentre


  The location on the earth's surface that experiences the most shaking
• The focus is shallow


  The shaking is worse at the surface
• Magnitude


  The power of the earthquake
• Seismometer


  The instrument used to measure the magnitude, recorded using the Richter Scale
• The Richter Scale is logarithmic. A magnitude 6.0 quake is 10X more powerful than a magnitude 5.0
• Earthquakes beneath the sea can generate tsunamis
• Tsunami waves


  • They can travel up to 900km/h
  • In the open ocean, the wave height is less than 1m
  • As the waves reach the shallower coast, they slow down, bunch up and wave height increases to up to 30m
• When a tsunami hits, it causes a powerful flood which can push several kilometres inland, causing widespread devastation
• Warning systems in the ocean can detect tsunamis, allowing early warning systems to be triggered, but this is only useful if the epicentre is some distance from the coast
• In March 2011, Japan was hit by an powerful (9.0) earthquake, which triggered a powerful tsunami 70km from the coast in Sendai Bay, it caused $235 billion damage and killed 16,000 people