earthquakes

• the focus is the part where pressure is released underground and where energy radiates from
• the strongest waves come from the focus
• the epicentre is the point directly above the centre of the earthquake on the earth's surface
• seismic waves are when energy is released from the focus in shock waves
• shallow-focus earthquakes are those where the focus is 0-70km under the earth's surface
• deep-focus earthquakes are where the focus is 70-700km
• which is more damaging? shallow or deep focus earthquakes?

  shallow - shock waves don't travel as far , cause less shaking at the surface
• what causes deep focus earthquakes?

  previously subjected crust moving towards the core, heating up or decomposing
• the deeper the focus the bigger the?

  tsunami?
• 3 types of waves

  primary

  secondary

  love
• primary waves are the fastest waves but cause the least damage
• secondary waves make the ground shake violently
• love waves cause significant damage

  • lead to crustal fracturing
  • travel across surface and have a large amplitude
• crustal factoring is when the Earth can visibly separate and deep fissures in the ground can be created
• secondary hazards of earthquakes

  • liquefaction
  • landslides
  • tsunamis
• what is liquefaction?

  when earthquakes compact loose sediment of silts, sand and gravel that are waterlogged

  • compact ground forces water to rise to the surface
• what causes tsunamis?

  seabed is displaced vertically - displaces large volumes of water in the ocean column , moves outwards from point of displacement
• wavelength of a tsunami?

  100km
• what is amplitude of tsunamis?

  height of wave
• how quickly do tsunamis move?

  700kph - slow down as they reach shallow water
• how can you tell if a tsunami is gonna happen?

  localised drop in sea level (drawback) , water is drawn back and up for use by approaching tsunami