Tsunamis??

• Case study

  2004 Boxing Day tsunami, Indonesia

  • epicentre in Banda Aceh, western Sumatra
  • devastating effects reached far beyond
  • magnitude 9 earthquake off coast of Tōhoku, Japan= tsunami in 2011
• causes

  generated by submarine earthquakes at subduction zones

  seabed displaced vertically -> dispatches large volume of water in ocean column -> moves outwards from point of displacement
• Characteristics

  Long wavelength at sea

  • wavelength = distance between two points of a wave
  • often >100km long
• characteristics

  short amplitude at sea

  • how like high it is
  • at sea ~1m in height -> barely noticeable
  • at land height can increase to >25m
• characteristics

  velocity

  • move v quickly
  • up to 700 kph in deep water
  • slow down in shallower water
• characteristics

  drawback

  • localised drop in sea level
  • water is drawn back and up for use of approaching tsunami
• characteristics

  wave train

  • way tsunami hits a coastline is like a series of waves