Case study: Tohoku, Japan

On 11 March 2011, a massive 9.0 earthquake occurred off the Japanese coastline at 14:46.

The epicentre was 43 miles east of Tohoku at a depth of 20 miles.

The earthquake lasted 6 minutes and caused a tsunami wave that reached heights of over 40 metres.

Photograph of earthquake destruction in Japan

Earthquake destruction in Japan

The plates involved

Japan is located in one of the most active earthquake zones on earth.

The Philippine plate and the Pacific plate are moving towards the much bigger continental Eurasian and North American plates.

The movement can be up to around 8cm each year.

This is a destructive plate margin where a subduction zone has formed.

The thin, oceanic Pacific plate is being forced (sub-ducted) underneath the much thicker continental Eurasian plate.

Friction has built up over time and when released this caused a massive ‘megathrust’ earthquake.

The amount of energy released in this single earthquake was equivalent to 600 million times the energy of the Hiroshima nuclear bomb.

Illustration showing a cross section of an earthquakeCross section of Tohoku earthquake

Short-term impacts

Impacts on peopleImpacts on the environment
Death and injury - 15,894 people died, 6,152 people were injured, 130,927 were displaced and 2,562 people remain missing.Fore and aftershocks - Scientists estimate that over 800 earthquakes of magnitude 4.5 or more were recorded following the main earthquake.
Nuclear crisis - A 9m high wave flooded the plants generators and electrical wiring. People lost energy immediately.Tsunami up to 40 m high devastated entire towns and resulted in the loss of thousands of lives. This caused a lot of damage and pollution up to 6 miles inland.
Flood defence disaster - Japan spent billions of dollars building anti-tsunami defences at heights of 12 m. The tsunami washed over them, rendering them totally ineffective.Land fall - some coastal areas experienced land subsidence as the earthquake dropped the beachfronts in some places by more than 50 cm.
Damage - 332,395 buildings, 2,126 roads, 56 bridges and 26 railways were destroyed or damaged. 300 hospitals were damaged and 11 were totally destroyed.
Blackouts - Around 4.4 million households in North-East Japan were left without electricity.

Long-term impacts

Impacts on peopleImpacts on the environment
Economy - The economic cost was US$235 billion, making this the most expensive natural disaster in world history. Land movement - The quake moved parts of North East Japan 2.4 m closer to North America.
Tsunami - Only 58% of people in the coastal areas followed the tsunami warnings and headed for higher ground. The waves hit 49% of those who did not follow the warning.Coastal changes - A 250 mile stretch of coastline dropped by 0.6 m, allowing the tsunami to travel further inland.
Nuclear power - The damage caused by the earthquake resulted in the meltdown of seven reactors. Radiation levels at one point were over eight times normal levels.Plate shifts - Geologists estimate that the Pacific plate has slipped westwards by between 20 and 40 m.
Transport - Japan’s transport network suffered huge disruptions. Sections of the Tohoku Expressway were damaged.Seabed shift - The seabed near the epicentre shifted by 24 m and the seabed off the coast of the Miyagi province has moved by 3 m.
Aftermath - The ‘Japan move forward committee’ thought that young adults and teenagers could help rebuild parts of Japan devastated by the earthquake.Earth axis moves - The earthquake moved the earth’s axis by between 10 and 25 cm, shortening the day by 1.8 microseconds.
Liquefaction occurred in many of the parts of Tokyo built on reclaimed land. 1,046 buildings were damaged