earthquakes

• Epicentre: is the point on the earth’s surface vertically above the focus earthquake damage tends to be greater at this point
• Focus: the location where the earthquake begins. The ground/rock ruptures at this spot, the place from which seismic waves radiate outward in all directions
• S wave: slower than P waves, second wave to reach a seismograph shear wave is a wave where the ground moves perpendicular to the direction of the travel of the wave can only travel through solid rock
• P wave: fastest wave first wave to be recorded by a seismograph compressional wave longitudinal earthquake wave travels through solid rock and liquids
• Earthquakes are vibrations in the Earth's crust that cause shaking at the surface.
• RISK = hazard (frequency and/or magnitude) x level of vulnerability

  Resilience level (ability of community to cope)
• Degg Model

  This shows the intersection between a hazardous natural event, such as an earthquake, hurricane or landslide and a vulnerable population which experiences human and/or economic loss, to create a disaster.
• love waves are the fastest and they move horizontally from side to side and generates the greatest damage
• rayleigh waves follow an elliptical motion which moves the ground up and down and side to side can be larger than other waves and result in most of the shaking effect
• ground shaking

  shaking of the ground is caused by a passage of seismic waves represents greatest hazards to humans due to collapsing of infastructure. intensity depends on the distance from epicentre geology and duration
• liquefaction

  loose sediment such as sand and silt combine with groundwater behave as a liquid can cause foundations of buildings to sink and collapse after an earthquake the water sinks deeper into the ground and the surface firms
• landslides

  earthquake creates stresses that moves weak slopes triggering landslides e.g avalanches. increases death toll and hampers rescue efforts
• tsunamis

  caused by a shallow focus under sea and earthquake creating displacements within the surface of the sea floor causing displacement in sea water . spreads out from epicentre . 80% occur in the pacific ring of fire