Japan earthquake 2011 Case Study

What?

An earthquake measuring 9.0 on the Richter Scale struck off Japan’s northeast coast, about 250 miles (400km) from Tokyo at a depth of 20 miles.

When?

The magnitude 9.0 earthquake happened at 2:46 pm (local time) on Friday, March 11, 2011.

Where?

The earthquake occurred 250 miles off the North East Coast of Japan’s main island Honshu.

Why?

Japan is located on the eastern edge of the Eurasian Plate. The Eurasian plate, which is continental, is subducted by the Pacific Plate, an oceanic plate forming a subduction zone to the east of Japan. This type of plate margin is known as a destructive plate margin. The process of subduction is not smooth. Friction causes the Pacific Plate to stick. Pressure builds and is released as an earthquake.

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 600 million times the energy of the Hiroshima nuclear bomb.

Scientists drilled into the subduction zone soon after the earthquake and discovered a thin, slippery clay layer lining the fault. The researchers think this clay layer allowed the two plates to slide an incredible distance, some 164 feet (50 metres), facilitating the enormous earthquake and tsunami.

So What?

The earthquake occurred at a relatively shallow depth of 20 miles below the surface of the Pacific Ocean. This, combined with the high magnitude, caused a tsunami (find out more about how a tsunami is formed on the BBC website).

The tsunami struck the northeastern coast of Honshu.

What were the primary effects of the 2011 Japan earthquake?

Impacts on people

Death and injury – Some 15,894 people died, and 26,152 people were injured. 130,927 people were displaced, and 2,562 remain missing.

Damage – 332,395 buildings, 2,126 roads, 56 bridges and 26 railways were destroyed or damaged. 300 hospitals were damaged, and 11 were destroyed.

Blackouts – Over 4.4 million households were left without electricity in North-East Japan.

Transport – Japan’s transport network suffered huge disruptions.

Impacts on the environment

Landfall – some coastal areas experienced land subsidence as the earthquake dropped the beachfront in some places by more than 50 cm.

Land movement – due to tectonic shift, the quake moved parts of North East Japan 2.4 m closer to North America.

Plate shifts – It has been estimated by geologists that the Pacific plate has slipped westwards by between 20 and 40 m.

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.

Earth axis moves – The earthquake moved the earth’s axis 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

What were the secondary effects of the 2011 Japan earthquake?

Impacts on people

Economy – The earthquake was the most expensive natural disaster in history, with an economic cost of US$235 billion.

Tsunami –  Waves up to 40 m in high devastated entire coastal areas and resulted in the loss of thousands of lives. This caused a lot of damage and pollution up to 6 miles inland. The tsunami warnings in coastal areas were only followed by 58% who headed for higher ground. The wave hit 49% of those not following the warning.

Nuclear power – Seven reactors at the Fukushima nuclear power station experienced a meltdown. Levels of radiation were over eight times the normal levels.

Transport –  Rural areas remained isolated for a long time because the tsunami destroyed major roads and local trains and buses. Sections of the Tohoku Expressway were damaged. Railway lines were damaged, and some trains were derailed. 

Aftermath – The ‘Japan move forward committee’ thought that young adults and teenagers could help rebuild parts of Japan devastated by the earthquake.

Impacts on the environment

Coastal changes – The tsunami was able to travel further inland due to a 250-mile stretch of coastline dropping by 0.6 m.

What were the immediate responses to the Japan 2011 earthquake?

• The Japan Meteorological Agency issued tsunami warnings three minutes after the earthquake.
• Scientists had been able to predict where the tsunami would hit after the earthquake using modelling and forecasting technology so that responses could be directed to the appropriate areas.
• Rescue workers and around 100,000 members of the Japan Self-Defence Force were dispatched to help with search and rescue operations within hours of the tsunami hitting the coast.
• Although many search and rescue teams focused on recovering bodies washing up on shore following the tsunami, some people were rescued from under the rubble with the help of sniffer dogs.
• The government declared a 20 km evacuation zone around the Fukushima nuclear power plant to reduce the threat of radiation exposure to local residents.
• Japan received international help from the US military, and search and rescue teams were sent from New Zealand, India, South Korea, China and Australia.
• Access to the affected areas was restricted because many were covered in debris and mud following the tsunami, so it was difficult to provide immediate support in some areas.
• Hundreds of thousands of people who had lost their homes were evacuated to temporary shelters in schools and other public buildings or relocated to other areas.
• Many evacuees came from the exclusion zone surrounding the Fukushima nuclear power plant. After the Fukushima Daiichi nuclear meltdown, those in the area had their radiation levels checked, and their health monitored to ensure they did not receive dangerous exposure to radiation. Many evacuated from the area around the nuclear power plant were given iodine tablets to reduce the risk of radiation poisoning.

What were the long-term responses to the Japan 2011 earthquake?

• In April 2011, one month after the event occurred, the central government established the Reconstruction Policy Council to develop a national recovery and reconstruction outlook for tsunami-resilient communities. The Japanese government has approved a budget of 23 trillion yen (approximately £190 billion) to be spent over ten years. Central to the New Growth Strategy is creating a ‘Special Zones for Reconstruction’ system. These aim to provide incentives to attract investment, both in terms of business and reconstruction, into the Tohoku region.
• Also, the central government decided on a coastal protection policy, such as seawalls and breakwaters which would be designed to ensure their performance to a potential tsunami level of up to the approximately 150-year recurrence interval.
• In December 2011, the central government enacted the ‘Act on the Development of Tsunami-resilient Communities’. According to the principle that ‘Human life is most important, this law promotes the development of tsunami-resistant communities based on the concept of multiple defences, which combines infrastructure development and other measures targeting the largest class tsunami.
• Japan’s economic growth after the Second World War was the world’s envy. However, over the last 20 years, the economy has stagnated and been in and out of recession. The 11 March earthquake wiped 5–10% off the value of Japanese stock markets, and there has been global concern over Japan’s ability to recover from the disaster. The priority for Japan’s long-term response is to rebuild the infrastructure in the affected regions and restore and improve the economy’s health as a whole.
• By the 24th of March 2011, 375 km of the Tohoku Expressway (which links the region to Tokyo) was repaired and reopened.
• The runway at Sendai Airport had been badly damaged. However, it was restored and reusable by the 29th of March due to a joint effort by the Japanese Defence Force and the US Army.
• Other important areas of reconstruction include the energy, water supply and telecommunications infrastructure. As of November 2011, 96% of the electricity supply had been restored, 98% of the water supply and 99% of the landline network.

Why do people live in high-risk areas in Japan?

There are several reasons why people live in areas of Japan at risk of tectonic hazards:

• They have lived there all their lives, are close to family and friends and have an attachment to the area.
• The northeast has fertile farmland and rich fishing waters.
• There are good services, schools and hospitals.
• 75% of Japan is mountainous and flat land is mainly found in coastal areas, which puts pressure on living space.
• They are confident about their safety due to the protective measures that have been taken, such as the construction of tsunami walls.

Japan’s worst previous earthquake was of 8.3 magnitude and killed 143,000 people in Kanto in 1923. A magnitude 7.2 quake in Kobe killed 6,400 people in 1995.