CASE STUDY- Japanese Tsunami 2011

  • Created by: 8cburton
  • Created on: 20-05-15 14:39

Nature of the hazard

  • 2 days before there had been major tremors peaking 7.2 on the richter scale
  • The earthquake measured 9.0 was the worlds 5th largest since 1990 and largest in Japan
  • The epicentre was 24km deep 72km off the coast of Sendai
  • Pacifc plate being subducted below Okhatsk plate
  • Horizontal crust displacement 50m
  • Sea bed raised 16m
  • Ground shook for 6min
  • Within 20min a huge tsunami developed
  • 5wks after the region had expereinced 420 aftershocks greater than magnitude 5.0 suggesting continual large scale crust adjustment.

Factors contributing to vulnerability

  • Only small earthquakes expected due to oceanic crust being very old and therefore should readily slide into mantle
  • Warping of pacific plate as it got stuck causing strain to build up
  • Ria coast - jagged coastline and inlets so waves are concentrated up rivers and bays
  • 70% Japan in mountainous forcing urban/ industry developement into narrow, low lying coastal areas
  • Soft reclaim land susceptable to landslides
  • Government officials too complacent.

Impact of event

  • Highest wave was 15 metres
  • Erosion of beached + dunes
  • Destruction of man made structures
  • 95% of all vegetation destroyed
  • 500km2 inundated in north-east Japan
  • Sediment transported 5km inland on the Sendai plain
  • Seawater remained on the surface for 2 months and salt crusts formed on the paddy fields as water slowly evaporated

Fukushima nuclear explosion

  • Power supply damaged so cooling system failed, water continued to generate steam. Fuel rodes go hotter + reacted with steam to form hydrogen gas. This melted, damaging power station structure. Pressure rose till explosion. Seawater used as emergency coolant, radioactive substances escaped and fires developed.
  • 80,000 people evacuated in a 12 mile…


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