tohoku japan tsunami 2011 case study

Case Study: How does Japan live with earthquakes?

Japan lies within one of the most tectonically active zones in the world. It experiences over 400 earthquakes every day. The majority of these are not felt by humans and are only detected by instruments. Japan has been hit by a number of high-intensity earthquakes in the past. Since 2000 there are have been 16000 fatalities as the result of tectonic activity.

Japan is located on the Pacific Ring of Fire, where the North American, Pacific, Eurasian and Philippine plates come together. Northern Japan is on top of the western tip of the North American plate. Southern Japan sits mostly above the Eurasian plate. This leads to the formation of volcanoes such as Mount Unzen and Mount Fuji. Movements along these plate boundaries also present the risk of tsunamis to the island nation. The Pacific Coastal zone, on the east coast of Japan, is particularly vulnerable as it is very densely populated.

The 2011 Japan Earthquake: Tōhoku

Japan experienced one of its largest seismic events on March 11 2011. A magnitude 9.0 earthquake occurred 70km off the coast of the northern island of Honshu where the Pacific and North American plate meet. It is the largest recorded earthquake to hit Japan and is in the top five in the world since records began in 1900. The earthquake lasted for six minutes.

A map to show the location of the 2011 Japan Earthquake

The earthquake had a significant impact on the area. The force of the megathrust earthquake caused the island of Honshu to move east 2.4m. Parts of the Japanese coastline dr[[ed by 60cm. The seabed close to the focus of the earthquake rose by 7m and moved westwards between 40-50m. In addition to this, the earthquake shifted the Earth 10-15cm on its axis.

The earthquake triggered a tsunami which reached heights of 40m when it reached the coast. The tsunami wave reached 10km inland in some places.

What were the social impacts of the Japanese earthquake in 2011?

The tsunami in 2011 claimed the lives of 15,853 people and injured 6023. The majority of the victims were over the age of 60 (66%). 90% of the deaths was caused by drowning. The remaining 10% died as the result of being crushed in buildings or being burnt. 3282 people were reported missing, presumed dead.

Disposing of dead bodies proved to be very challenging because of the destruction to crematoriums, morgues and the power infrastructure. As the result of this many bodies were buried in mass graves to reduce the risk of disease spreading.

Many people were displaced as the result of the tsunami. According to Save the Children 100,000 children were separated from their families. The main reason for this was that children were at school when the earthquake struck. In one elementary school, 74 of 108 students and 10 out of 13 staff lost their lives.

More than 333000 people had to live in temporary accommodation. National Police Agency of Japan figures shows almost 300,000 buildings were destroyed and a further one million damaged, either by the quake, tsunami or resulting fires. Almost 4,000 roads, 78 bridges and 29 railways were also affected. Reconstruction is still taking place today. Some communities have had to be relocated from their original settlements.

What were the economic impacts of the Japanese earthquake in 2011?

The estimated cost of the earthquake, including reconstruction, is £181 billion. Japanese authorities estimate 25 million tonnes of debris were generated in the three worst-affected prefectures (counties). This is significantly more than the amount of debris created during the 2010 Haiti earthquake. 47,700 buildings were destroyed and 143,300 were damaged. 230,000 vehicles were destroyed or damaged. Four ports were destroyed and a further 11 were affected in the northeast of Japan.

There was a significant impact on power supplies in Japan. 4.4 million households and businesses lost electricity. 11 nuclear reactors were shut down when the earthquake occurred. The Fukushima Daiichi nuclear power plant was decommissioned because all six of its reactors were severely damaged. Seawater disabled the plant’s cooling systems which caused the reactor cores to meltdown, leading to the release of radioactivity. Radioactive material continues to be released by the plant and vegetation and soil within the 30km evacuation zone is contaminated. Power cuts continued for several weeks after the earthquake and tsunami. Often, these lasted between 3-4 hours at a time. The earthquake also had a negative impact on the oil industry as two refineries were set on fire during the earthquake.

Transport was also negatively affected by the earthquake. Twenty-three train stations were swept away and others experienced damage. Many road bridges were damaged or destroyed.

Agriculture was affected as salt water contaminated soil and made it impossible to grow crops.

The stock market crashed and had a negative impact on companies such as Sony and Toyota as the cost of the earthquake was realised.  Production was reduced due to power cuts and assembly of goods, such as cars overseas, were affected by the disruption in the supply of parts from Japan.

What were the political impacts of the Japanese earthquake in 2011?

Government debt was increased when it injects billions of yen into the economy. This was at a time when the government were attempting to reduce the national debt.

Several years before the disaster warnings had been made about the poor defences that existed at nuclear power plants in the event of a tsunami. A number of executives at the Fukushima power plant resigned in the aftermath of the disaster. A movement against nuclear power, which Japan heavily relies on, developed following the tsunami.

The disaster at Fukushima added political weight in European countries were anti-nuclear bodies used the event to reinforce their arguments against nuclear power.

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Japan Earthquake 2011

Japan earthquake 2011 case study.

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.

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

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

Japan 2011 Earthquake map

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 .

2011 Japan Earthquake Map

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).

Areas affected by the 2011 Japanese earthquake.

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?

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.

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 .

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HISTORIC ARTICLE

Mar 11, 2011 ce: tohoku earthquake and tsunami.

On March 11, 2011, Japan experienced the strongest earthquake in its recorded history.

Earth Science, Oceanography, Geography, Physical Geography

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Learning materials.

• Click below to see a MapMaker Interactive map displaying tectonic activity surrounding the Tohoku earthquake and tsunami.

On March 11, 2011, Japan experienced the strongest earthquake in its recorded history. The earthquake struck below the North Pacific, 130 kilometers (81 miles) east of Sendai, the largest city in the Tohoku region , a northern part of the island of Honshu.

The Tohoku earthquake caused a tsunami . A tsunami—Japanese for “ harbor wave ”—is a series of powerful waves caused by the displacement of a large body of water. Most tsunamis, like the one that formed off Tohoku, are triggered by underwater tectonic activity , such as earthquakes and volcanic eruptions . The Tohoku tsunami produced waves up to 40 meters (132 feet) high, More than 450,000 people became homeless as a result of the tsunami. More than 15,500 people died. The tsunami also severely crippled the infrastructure of the country .

In addition to the thousands of destroyed homes, businesses, roads, and railways, the tsunami caused the meltdown of three nuclear reactors at the Fukushima Daiichi Nuclear Power Plant . The Fukushima nuclear disaster released toxic , radioactive materials into the environment and forced thousands of people to evacuate their homes and businesses.

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October 19, 2023

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On This Day: 2011 Tohoku Earthquake and Tsunami

On March 11, 2011, a magnitude (Mw) 9.1 earthquake struck off the northeast coast of Honshu on the Japan Trench. A tsunami that was generated by the earthquake arrived at the coast within 30 minutes, overtopping seawalls and disabling three nuclear reactors within days. The 2011 Tohoku Earthquake and Tsunami event, often referred to as the Great East Japan earthquake and tsunami , resulted in over 18,000 dead, including several thousand victims who were never recovered.

The deadly earthquake was the largest magnitude ever recorded in Japan and the third-largest in the world since 1900. 

How It Happened

The 2011 event resulted from thrust faulting on the subduction zone plate boundary between the Pacific and North America plates, according to the U.S. Geological Survey .

This region has a high rate of seismic activity, with the potential to generate tsunamis. Past earthquakes that generated tsunamis in the region have included the deadly events of 1611 , 1896 , and 1933 .

The March 11, 2011 earthquake generated a tsunami with a maximum wave height of almost 40 meters (130 feet) in the Iwate Prefecture . Researchers also determined that a 2,000-kilometer (1,242-mile) stretch of Japan’s Pacific coast was impacted by the tsunami.

Following the earthquake, a tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a significant nuclear accident . All three nuclear cores largely melted in the first three days. 

As of December 2020, the Japan National Police Agency reported 15,899 deaths, 2,527 missing and presumed deaths, and 6,157 injuries for the Great East Japan event.

In Japan, the event resulted in the total destruction of more than 123,000 houses and damage to almost a million more. Ninety-eight percent of the damage was attributed to the tsunami. The costs resulting from the earthquake and tsunami in Japan alone were estimated at $220 billion USD. The damage makes the 2011 Great East Japan earthquake and tsunami the most expensive natural disaster in history. 

Although the majority of the tsunami’s impact was in Japan, the event was truly global. The tsunami was observed at coastal sea level gauges in over 25 Pacific Rim countries, in Antarctica, and on the west coast of the Atlantic Ocean in Brazil.

The tsunami caused $31 million USD damage in Hawaii and $100 million USD in damages and recovery to marine facilities in California. Additionally, damage was reported in French Polynesia, Galapagos Islands, Peru, and Chile. 

Fortunately, the loss of life outside of Japan was minimal (one death in Indonesia and one death in California) due to the Pacific Tsunami Warning System and its connections to national-level warning and evacuation systems. 

From Peril to Preparedness

To learn from the tragedy in Japan, researchers collected extensive data on tsunami wave forces and building performance. This facilitated improvement in tsunami mitigation strategies, such as building codes. Over 6,200 tsunami wave measurements were collected in Japan and the Pacific region. 

Several thousands of lives across the world were lost to large, far-afield tsunamis prior to the establishment of the Pacific Tsunami Warning System in 1965. The Great East Japan earthquake and tsunami demonstrated that despite the severity of the natural hazard the investment in the warning system has been a success. 

Japan is often considered the country most prepared for tsunamis but still lost numerous lives in this event. Nonetheless, experts believe many lives were saved in Japan and elsewhere due to the existing warning and mitigation systems.

An effective tsunami warning system relies on the free and open exchange and long-term management of global data and science products to mitigate, model, and forecast tsunamis. NCEI is the global data and information service for tsunamis. Global historical tsunami data, including more information about the Great East Japan earthquake and tsunami, are available via interactive maps and a variety of web services.

For more information on how you can prepare for a tsunami, visit the National Tsunami Hazard Mitigation Program . Also, visit NCEI’s Natural Hazards website for more earthquake and tsunami data, images, and educational materials.

Kong, L., P. Dunbar, and N. Arcos (2015). Pacific Tsunami Warning System: A Half-Century of Protecting the Pacific 1965-2015. Honolulu: International Tsunami Information Center.

Satake, K. (2014). Chapter 24, The 2011 Tohoku, Japan, Earthquake and Tsunami. Extreme Natural Hazards, Disaster Risks and Societal Implications, Cambridge University Press, p. 340-351.

UNESCO/IOC (2012). Summary Statement from the Japan - UNESCO - UNU Symposium on The Great East Japan Tsunami on 11 March 2011 and Tsunami Warning Systems: Policy Perspectives 16 - 17 February 2012

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Crisis Management of Tohoku; Japan Earthquake and Tsunami, 11 March 2011

M zaré.

1 International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

S Ghaychi Afrouz

2 Mining Engineering, School of Mining Engineering, University College of Engineering, University of Tehran, Tehran, Iran

The huge earthquake in 11 March 2012 which followed by a destructive tsunami in Japan was largest recorded earthquake in the history. Japan is pioneer in disaster management, especially earthquakes. How this developed country faced this disaster, which had significant worldwide effects? The humanitarian behavior of the Japanese people amazingly wondered the word’s media, meanwhile the management of government and authorities showed some deficiencies. The impact of the disaster is followed up after the event and the different impacts are tried to be analyzed in different sectors. The situation one year after Japan 2011 earthquake and Tsunami is overviewed. The reason of Japanese plans failure was the scale of tsunami, having higher waves than what was assumed, especially in the design of the Nuclear Power Plant. Japanese authorities considered economic benefits more than safety and moral factors exacerbate the situation. Major lessons to be learnt are 1) the effectiveness of disaster management should be restudied in all hazardous countries; 2) the importance of the high-Tech early-warning systems in reducing risk; 3) Reconsidering of extreme values expected/possible hazard and risk levels is necessary; 4) Morality and might be taken as an important factor in disaster management; 5) Sustainable development should be taken as the basis for reconstruction after disaster.

Introduction

The magnitude 9.0 Japan’s Tohoku Earthquake occurred at 14:46 local time on Friday, 11 March 2011, 125 km east coast of Honshu and 380 km far from Tokyo and rattled the large parts of Japan and some part of east China and Russia with 30 km depth of the hypocenter ( 1 ). This earthquake that lasted approximately 3 minutes (170 seconds) caused a 130 km long by 159 km wide rupture zone on the pacific plate subduction zone and followed by a huge tsunami with more than 40 meter waves. The destructive aftermaths of this incident made an irreparable disaster not only for the Japan, but also for the whole world because except for the enormous death toll and debris, the damages of nuclear power plants were a hazardous unexpected tragedy.

Casualties and damages

According to the report of the Japanese National Police Agency, 15854 dead, 3167 missing and 26992 injured across twenty prefectures are the result of this devastating earthquake and tsunami which ruined more than 125000 buildings. Moreover, it caused long blackouts for more than 4.4 million buildings and left 1.5 million buildings out of water for days ( 2 ), also large fires were triggered one after another even for weeks after the main quake. Explosion and demolition of the Fukushima I Nuclear Power Plant (Fukushima Daiichi), which generated radioactive contamination near the plant’s area with irreversible damages to the environment, was one the most significant issues of this catastrophe and ranked 7 (the most sever level for nuclear power plant) based on the International Nuclear Event Scale, similar to the Chernobyl disaster on 26 April 1986 ( 3 ). Therefore, it is not strange to consider to this earthquake as the most important destructive seismic event of the beginning of the twenty first century in the advanced industrial world.

Losses intensified by hit of the tsunami as the statistics shows it was more fatal ( Fig. 1 ) and also more buildings destroyed by its strike; However, the quake was the main cause of the partial damage of buildings ( 4 ). Figure 2 manifests the building losses distribution through affected areas and Fig. 3 reveals the relative impact of the earthquake vs. tsunami in each prefecture of Japan ( 4 ).

Division of total 19100 death and missed people by the reason as of 10th March 2012 (CATDAT)

Building damage distribution (CATDAT)

The relative impact of the earthquake vs. the tsunami in each location

Seismology and Seismic History

This mega thrust earthquake is categorized as a great earthquake with the magnitude more than 8 in scientific seismological classification ( 5 ). Over 1000 aftershocks, some of which were larger than the recent catastrophic earthquakes in Iran such as Bam, Iran 2003, hit the area since the main shock. Regardless of the consequent tsunami, the Tohoku Sendai Earthquake (2011) is the largest recorded earthquake in the history of Japan in terms of magnitude while the territory of Japan is known by numerous and critical earthquakes. There are two momentous calamitous earthquakes in history of Japan: The great Kanto earthquake with magnitude of 7.9 on 1 September 1923 which destroyed Tokyo and Yokohama rigorously by the severe quake and subsequent fires and caused more than 143000 deaths ( 6 , 7 ); and the Kobe earthquake (also known as Hanshin- Awaji earthquake) with magnitude of 6.9 on 17 January 1995 that left more than 6400 demises ( 6 , 8 ). The Kanto incident is still the deadliest earthquake in Japanese history and the Kobe earthquake was the most costly natural disaster of the world since Tohoku Earthquake 2011 ( 9 ).

Methodology

Japan crisis management system.

Japan has an overall population of 127 million and is one of the most densely populated countries in the world (340 persons per Km), where the population highly concentrated around Tokyo ( 6 ). This earthquake-prone country as a pioneer in crisis management has a comprehensive plan for preparing against disasters, consists of the Central Council for Accident Prevention, chaired by Prime Minister, set of cohesive rules for immediate response to all of the unexpected incidents, the advanced research system and the extensive public education about disasters. As the result of this plan, in the case of an accident, people, government officials and rescue departments know exactly what to do while the alarm is sounded, without chaos.

It was after the disastrous Kobe earthquake of 17 January 1995 (M6.9) that crisis management of Japan greatly promoted since the government set up a GIS system and a general computer network. This system contains different subsystems to operate all disaster related functions from prevention before the disaster to damage evaluation after it ( 10 ). Additionally, the most advanced earthquake and tsunami early warning system of the whole world is installed in Japan during 2003 to 2007, which is one of the main parts of this crisis management system. This warning system had a considerable role in Tohoku 2011 earthquake to reduce losses and save lives. Several Japanese media such NHK channel and also mobile phone networks have the most responsibility of broadcasting the news of early warning system.

In management of the 11 March 2011 crisis, one of the most facilitative factors for emergency managers was proper behavior of people who follow the commands cautiously. In other words, the “ social capital” in this country had a significant role in recovery after the incident as people’s high respect to roles and moral values and their solidarity prevent them from influx for aid and looting and motivate them to consider the public benefits instead of self-interests.

Response to the disaster

Immediately after the event, The Government of Japan (GOJ) held National Committee for Emergency Management, headed by Prime Minister. The government declared an emergency in effected area and dispatched the Japan Self Defense Forces for rescue operations ( 11 ). All ministries and departments such as Foreign Ministry, Ministry of Transport and Ministry of Health were involved in this response, also local offices of disaster response in all prefectures begins their operations as their duty was already clear. The Ministry of Health was in charge of preparing suitable vehicles for supplying water and assigning hospitals for remedy of casualties and people who have been exposed to radiation. Ministry of Agriculture, Forestry and Fisheries with Ministry of Finance were responsible for providing food, portable toilet, blanket, radio, gasoil, torch, dry ice and other essential things. By the command of the government, all of the main highways in north of the country were completely occupied for emergency response activities. Besides, the transport systems includes subway, shipping and the Shinkansen bullet train ceased their activity in Sendai and Tokyo instantly after the quake.

Moreover, at the day of event the Government of Japan declared “the state of nuclear emergency” due to the threat posed by reactors in two Fukushima nuclear power plants (I and II) and 140,000 residents within 20 km of the plant evacuated. At 15:36 JST (Japan Standard Time) on 12 March, there was an explosion in the reactor building at Unit 1 in Fukushima Daiichi (I) power plant. At 11:15 JST on 14 March, the explosion of the building surrounding Reactor 3 occurred. An explosion at 06:14 JST on 15 March in Unit 2, damaged the pressure-suppression system. When the disaster began on 11 March 2011, reactor unit 4 was shut down for periodic inspection and all fuel rods had been transferred to the spent fuel pool on an upper floor of the reactor building. On 15 March, an explosion damaged the fourth floor rooftop area of the unit 4 reactor.

Japanese Red Crescent Society (JRC), which had a substantial role in initial relief operations and temporary housing, deployed its teams promptly. JRC performed properly for accommodation of refugees and evacuees in schools, public buildings, and shelters. This society adapted its operations to all other rescue organizations and NGOs, which deployed to the area later.

Construction of temporary housing in quakestricken prefectures was begun 8 days after the event and the first set of buildings was expected to be ready within a month ( 12 ). In addition to medical aids, therapists and social workers were dispatched to the affected zone by Health ministry and then in coming days the concentration of treatments was shifting to psychotherapy from physical sicknesses. In addition, this Ministry performed required actions in order to control and inhibit infectious diseases and encouraged people to use masks ( 2 ).

Fire was reported in eight prefectures after the quake. Fire suppression of gas pipeline took a few days and fires in Cosmo Oil Installations and some other refineries lasted 3 days. Generally, the number of fires increased from 44 to 325 in a week, but its growth rate declined. All the fires, which were triggered after the earthquake, were under control of Japanese Police and it can be said that they could prosperously cease and extinguish them ( 13 ). On the other hand, these fires and breakdown of six out of nine oil factories faced the affected areas with fuel shortage. The gas pipeline repairing operation had a slow progress, too. Therefore, about one million liter gasoline per day had been carried to the damaged areas by tankers and then by cargo train in order to compensate lack of fuel. Low displacement capacity of oil and coal shipments caused delays in delivering fuel loads, which were importing from countries such as South Korea and Russia, to consumers ( 13 ).

Due to the shutting down of the power plants which were cracked by the quake and tsunami, authorities begun imposing sporadic power cuts nationwide to make up for production losses. Correspondingly, large factories like Toyota and Sony halted their production activities and many citizens in Kanto reduced their power consumption in order to abridge the time of blackouts ( 14 ).

Nuclear crisis

There are 54 reactors in Japan, but since the tsunami on March 2011 that destroyed Fukushima plant ( Fig. 4 ) and triggered the world’s worst nuclear crisis in 25 years, the government did not allow to restart any reactor that have undergone maintenance due to public safety ( 15 ). The first nuclear power plant of Japan was initiated with collaboration of English corporations in 1973, but these kinds of power plants then developed by American technology. All the 11 reactors in Fukushima 1, Fukushima 2, Onagawa and Tokai nuclear power plants automatically safe shut down after the quake; however, arrival of tsunami debris with high waves damaged reactor’s cooling systems and eventually, resulted hazardous explosions. This could have been prevented if the designers had estimated the probable maximum altitude of the tides more prudently. The explosion occurred in 4 of the 6 reactors of Fukushima 1 power plant one after another, while the unit 3 reactor was more damaged and more intensively contaminated the surrounding area. A few hours before each of these explosions, authorities warned about the cooling system breakdown, ordered to evacuate neighboring people and tried to drop the pressure of vapors, but in all of them the hydrogen explosion finally happened.

Fukushima 1 NPP explosion, 14 March 2011 (DigitalGlobe)

The owner of the Fukushima Plant, The Tokyo Electric Power Company (TEPCO), is accused of mismanagement and hiding the truth about the real damage caused by the disaster at the expense of saving the company ( 16 ). Moreover, according to reports, it was expected that TEPCO safely shutdown reactors of Fukushima 1 nuclear power plant approximately a month before the 11 March earthquake, but apparently the company avoided this action because of economic issues.

Over 140 thousand residents were evacuated from 20 Km around the Fukushima plant. Radiation penetrated in foods and drinking water in 30 kilometer far from the evacuated area, and authorities inhibited distribution of these polluted foodstuffs ( 13 ). U.S. Department of Energy announced a wide area beyond 80-kilometer radius around the Fukushima plant is affected by radiation ( 17 ).

The explosion of Fukushima power plant and its aftermaths aroused public concerns about nuclear energy in Japan and other earthquake prone countries. Consequently, other power plants, which were not resistant to the probable future quakes with magnitude more than 8, ceased they activity gradually sequentially by the command of The Prime Minister. TEPCO shut its last operating nuclear reactor in 26 March 2012 for regular maintenance, leaving just one running reactor supplying Japan’s creaking power sector ( 15 ). Then again, on 10 April 2012 (less than a month later), as the summer arrives, while Japan is going to struggle with electricity shortage, the government planned to restart one of the atomic plants in Kansai after approval its safety ( 18 ) and faced with people’s disagreement.

Furthermore, the nuclear crisis has led to growing opposition against atomic power plants in other countries, particularly in Germany, where thousands of citizens participated in an anti-nuclear demonstration. This disapproval also affected the regional election results unbelievably. In the state of Baden-Wurttemburg, which traditionally had gone with Christian Democratic Union party for 58 years, most of people voted for the Green Party who was against with 17 nuclear reactors in this country ( 19 ).

Results: Crisis consequences

The 11 March 2011 earthquake had many deleterious environmental impacts that take a long time to recover. Apart from radioactive materials dispersed due to nuclear plant explosions and discharging polluted radioactive water of cooling systems to the sea, the subsequent tsunami induced huge amount of debris contains building materials, broken boats, cars, trees and etc. that cause environmental harmful issues.

Radioactive pollutions and radiations as the most harmful repercussions of the earthquake induced fear and concern among resident. Most evacuees did not return to their home even after the safety of the regions was assured. However, the government tried hard to convince people to return to their homes by checking and promulgation the radiation doses constantly, but just the population of old people gradually increased. Therefore, satisfying young people to come back will be a demanding challenge for the government.

• A year after the event, anecdotal evidence suggests that fear of radiation, rather than contamination itself, is triggering stress-related problems among nuclear evacuees ( 20 ), despite the experts emphasized that the doses are too low to develop cancer. Even in more distant areas, where completely secure, parents do not allow their children to play outside. Although there have been no recorded deaths from radiation in Fukushima, according to the Yomiuri Shimbun newspaper, psychological trauma associated with evacuation, pneumonia and heart disease were much more fatal based on statistics. Therefore, in months after the event, Japanese Red Cross concentrated on mental health issues.
• Also, the tsunami had adverse effects on agriculture and requires long-term reconstruction at least for 2 or 3 years. In addition, the fishing industry faced to critical continuing problems. Most reports acknowledged that Japan’s food exports could be limited by Japan’s current Production and supply shortages, along with boosting food safety concerns and possible long-term radiation threats to its food production, in contrast possibly its need for food imports will increase in future ( 21 ).
• Moreover, since Japan is a country covered by jungles, wooden houses are very prevalent in this country and despite the dropping rate of wood imports in recent decade, due to boom reduction of this kind of homes; the Tohoku earthquake caused a 70% rise in wood import rate by enhancement of the wood demand. This made a competition for wood exporters from different countries such as Australia, America, and China.
• One of the important impacts of the Fukushima power plant explosion is its psychological consequences. Regardless of common diseases such as infectious ones that break out after earthquakes, the radioactive contamination permeated to the residential areas where people was living, working and planting brought a ten times fatal disease, which is hopelessness and untruthfulness. People know they should leave anything they had include home and agriculture plant and this lead them to an ambiguous future which is unstable and they should build everything from beginning. The increase in number of suicides in power plant’s surrounding areas even far from them and farmers concern about safety of their productions and land even 100 kilometers far from the affected zone prove the strength and influence of this issues.
• Japan should also challenge with the problem of enhancing of unemployment. Large number of refugee and evacuees left their home and moved to other cities. Also, workers of car and electronic factories are now jobless by factory closure so they are forced to immigrate ( 22 ). Japanese government created around 20 thousands of jobs in the emergency measures to combat the effects of the disaster in a month, but the number of the unemployed ones was much more than created jobs ( 23 ). Additionally, women especially in rural areas, who used to were involved in tough works such as agriculture and fishing, after the disaster have to work in other posts and try different occupations in order to help to family economic. Many of these women take apart in protests against Fukushima power plant issues in Tokyo in October and November 2011. It seems that this earthquake has modified the women life style in affected prefectures as now they have more important roles in family issues and it is big change in an almost traditional male-dominated Japan.
• Following the shutting, the Fukushima power plant, on February 2012, the House Foreign Relations Committee off Japan approved to export its nuclear equipment to Vietnam and Jordan. Also Japanese companies signed agreements with India, Bangladesh, and Turkey about construction, operation, and management of nuclear power plants in these countries, despite environment activist’s oppositions in recent months against these transactions and their high costs and permanent detriments for humans and earth. Actually, the nuclear power in spite its approximate low costs, have many hazardous disadvantages that the Japan 2011 accident and the Chernobyl 1986 are good samples for this fact. Unfortunately, developing countries do not consider these consequences and endanger the environment and people’s lives while Japanese authorities are just accenting their own country’s benefits.

In Tohoku earthquake and tsunami of 11 March 2011 despite the unprecedented scale of the quake itself, infrastructures and buildings mostly remained standing and proved the resilience of Japan is planning laws especially in constructions and earthquake technology. Hence, if the earthquake had been the sole problem, then Japan could have claimed for itself a momentous prosperous in planning for the impact of a major earthquake. The reason of Japanese plans failure was the large-scale tsunami, which had higher waves than what was assumed in designing. In addition, the fact that Japanese authorities considered economic benefits more than safety and moral factors exacerbate the situation. Even after the disaster, this country just cared about economic benefits and sought to export its technology to other countries.

However, this disaster was a motivation for people and governments worldwide to replace clean energy with the hazardous one and it was a reminder to decommissioning the old and unsafe operating power plants. Thus, the Metsamor nuclear power plant in Armenia, Iran’s neighboring country, is a critical threat in the region with high seismic risk. Governments had to plan long-term and costly solutions to replace the nuclear energy with clean and renewable forms of it with respect to criteria and moral values, not only the benefits.

Although energy issues and management of power plant’s crisis was a blind spot in Tohoku disaster management, Japanese social ethics and their manner in dealing with the problem were the most advantageous points. Discipline, maintaining calm, public confidence in managers and scientific management based on the plans helped to improve the situation more quickly ( Figure-5 ). Long queues of Japanese People for food and facilities instead of chaos, which we mainly consider in developing countries, could be a good proof for other countries that enterprising on educating people about how to act in crisis is very operative and effective in enhancement of disaster management.

These two photos taken over a six-month period showing aftermath of the March 11, 2011, tsunami and its cleanup progress in Wakabayashi-ward in Sendai, Miyagi Prefecture, in northeastern Japan. ( pacificcitizen.org )

The 11 march 2011 earthquake was an alarm for seismologist all over the world, particularly in Tehran as a capital city, to revise their methods and evaluation of estimating the plausible time and magnitude of earthquake. It could be an alarm for us to be more meticulous and cautious about the earthquake hazard as prepared and industrialized Japan with the most modernized technology confronted many extensive troubles, which were out of their predictions. Now we should ask this question “how much we are prepared in an earthquake prone country with a capital located exactly on active faults?”

Ethical considerations

Ethical issues (Including plagiarism, Informed Consent, misconduct, data fabrication and/or falsification, double publication and/or submission, redundancy, etc) have been completely observed by the authors.

Acknowledgments

The authors declare that there is no conflict of interests. The authors appreciate the assistance of IIEES and Tehran university colleagues for finalizing this study, specially H.R. Jalilian, M.H Pishahang and Z. Hejazi.

A method for tsunami risk assessment: a case study for Kamakura, Japan

• Original Paper
• Open access
• Published: 26 May 2017
• Volume 88 , pages 1451–1472, ( 2017 )

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• Non Okumura 1 ,
• Sebastiaan N. Jonkman 1 ,
• Miguel Esteban 2 ,
• Bas Hofland 1 &
• Tomoya Shibayama 3  

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This paper presents a methodology for tsunami risk assessment, which was applied to a case study in Kamakura, Japan. This methodology was developed in order to evaluate the effectiveness of a risk-reducing system against such hazards, also aiming to demonstrate that a risk assessment is possible for these episodic events. The tsunami risk assessment follows these general steps: (1) determination of the probability of flooding, (2) calculation of flood scenarios, (3) assessment of the consequences and (4) integration into a risk number or graph. The probability of flooding was approximated based on the data provided by local institutes, and the flood scenarios were modeled in 1D using the Simulating WAves till SHore model. Results showed that a tsunami in Kamakura can result in thousands of casualties. Interventions such as improvements in evacuation systems, which would directly reduce the number of casualties, would have a large influence in risk reduction. Although this method has its limits and constraints, it illustrates the value it can add to existing tsunami risk management in Japan.

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1 Introduction

1.1 general.

On March 11, 2011, the Tohoku Earthquake and Tsunami devastated a large section of the Tohoku coastline of northern Japan. This disaster resulted in 15,867 casualties, with 2909 still missing as of 2012 (Yamao et al. 2015 ).

The challenge of reducing the vulnerability of coastal areas to tsunamis has been widely recognized and discussed among the government and scientific community. Before the 2011, event flood protection measures were designed according to water levels set by cases of smaller earthquakes, where the tsunami heights were underestimated. In response to the 2011 tsunami, a broad categorization that separates tsunamis into two protection levels has been made. A Level 1 tsunami represents an event with a return period of several decades to 100+ years, having lower inundation heights than a Level 2 event, which would have return periods between every few hundred to a few thousand years (potentially having inundation height of up to 20–30 m for the case of Tohoku). This concept also indicates that the function of coastal structures is to attempt to protect property against Level 1 events, whereas evacuation measures should be designed with Level 2 events in mind (Shibayama et al. 2013 ). Also, it is worth mentioning how there appears to be an empirical relationship between maximum tsunami height, minimum tsunami wave arrival time and potential risks to human life. Essentially, if residents have enough time to evacuate before defenses are overcome, they have a higher possibility of survival (Yamao et al. 2015 ).

A risk-based approach is applied in the flood management in the Netherlands (Jonkman et al. 2008 ; Jongejan and Maaskant 2015 ) and several other countries around the world, such as the UK (Hall et al. 2003 ), USA (IPET 2009 ) and China (Jiabi et al. 2013 ). The approach considers return periods of the hazard as well as their resulting damage and could offer some value to coastal risk managers in Japan. A study has already been made regarding a multilayer safety system in Tohoku, Japan, separately assessing the performance of each safety measure and their efficiency, and the implications of the use of multilayered safety in flood risk management (Tsimopoulou et al. 2012 ).

The risk-based approach to flood protection combines the knowledge on the probability of the occurrence of flood events with their consequences, such as damage to buildings and the loss of life. The approach aims to design and evaluate flood protections according to the risk, aiming to avoid the underestimation of hazards.

The objective of this article is to show how a general tsunami risk framework can be formulated and then proceed to quantitatively determine and evaluate this risk. The framework is derived from the flood risk assessment framework used in the Netherlands (Jonkman et al. 2008 ; Jongejan and Maaskant 2015 ; Jonkman and Schweckendiek 2015 ) and other countries for coastal and riverine flooding. The analyses carried out in this present research focus on the direct damage to buildings and potential loss of life, which are the most significant types of consequences. Results are presented for a case study that was made for Kamakura city, located 50 km southwest of Tokyo, which has residential areas and sightseeing spots, and would only have a small amount of time available for evacuation in the case of a nearshore tsunami. For this location, the risk reduction due to different interventions such as improvements in evacuation infrastructure and dike heightening is quantified, and the merits of the various interventions are discussed.

The article is structured as follows. The remainder of Sect.  1 gives the background information of the case study area of Kamakura in Japan. The methods used for the flood risk assessment are summarized in Sect.  2 . Results are presented in Sect.  3 . A discussion of the results is presented in Sect.  4 , in which a preliminary risk-reduction solution is introduced, and the advantages of using a risk-based approach are discussed. Concluding remarks are given in Sect.  5 .

1.2 Case study in Kamakura, Japan

Kamakura is a historical coastal city located in Sagami bay, and was at one time one of the two capitals of Japan, meaning that it is endowed with significant cultural heritage. The city has a population of 173,000 people (Kanagawa Prefectural Government 2016 ) and had up to 21.96 million tourists visiting it in 2014 (Kamakura City Office 2016 ), illustrating its importance to the country and the economy (Carlos-Arce et al. 2017 ). The coastline around the city is open and concave, which is expected to concentrate a tsunami’s energy and likely result in high inundation heights shortly after a nearshore event. The North American Plate, Pacific Plate and the Philippine Sea Plate meet approximately 300 km away. There is also the Sagami Trough located just outside of the bay area, along with the Nankai Trough, which is also feared to have the potential to cause a large tsunami in the near future (Yamao et al. 2015 ).

Kamakura has experienced seven recorded tsunamis in its history, the most recent one resulting from the Great Kanto earthquake in 1923 (The Headquarters for Earthquake Research 2016 ). Unfortunately, most of the tsunami records do not offer precise data, as they took place too far in the past (Carlos-Arce et al. 2017 ). Existing protection measures in Kamakura include a road embankment (which would behave like a dike in the event of a tsunami) built along the coast to a level of around +3 m (relative to MSL), designed against storm surge and wind waves, and emergency management measures, such as a hazard map illustrating the locations of evacuation centers (Kamakura City Office 2016 ; Carlos-Arce et al. 2017 ). Note that later evacuation centers will be neglected in the baseline case of this study.

2 Methodology

2.1 general.

The methods for the tsunami risk assessment, which are derived from the framework used in the Netherlands, include four main steps: (1) determination of the probability of flooding, (2) calculation of flood scenarios, (3) assessment of the consequences and (4) integration into a risk number or graph. The risk is quantified based on the results from these steps. The risk reduction due to interventions is also quantified and evaluated. In theory, the estimation of the risk should be based on a fully probabilistic approach, which considers all the possible scenarios and their consequences. Due to limitations in time and resources, a simplified approach is usually chosen, where a limited number of flood scenarios are selected and elaborated upon.

Elements of risk identification and analysis have been conducted all over the Japanese coasts by prefectural governments, and evacuation plans have been made by cities and wards as a part of risk management strategies (Central Disaster Management Council of Japan 2013 ). Tsunami models were run in 2D, and evacuation behavior was modeled with respect to tsunami arrival time and human behavior (Goto et al. 2012 ; Mas et al. 2012 ). However, complete risk assessments and evaluations including cost-benefit assessments were generally not performed. Tsunami risk assessments in the context of early warning and response have been studied in a case study in Indonesia (Strunz et al. 2011 ).

In this study, the authors essentially followed the methodology outlined above. One difference with risk management for the case of the Netherlands is that there is a certain low-lying area (polder) that is completely flooded after a certain water level is reached, while for the case of Japan (with coasts sloping upwards behind the beaches to hills and mountains) almost every tsunami will result in damage, the extent of which will vary according with the magnitude of the event. Each scenario refers to a different tsunami height along the coast, which is assumed to have one unique resulting pattern of flooding. The consequences of the selected flood scenarios have been analyzed by means of deterministic methods. By combining the probability of the flooding scenarios and their consequences, the risk can be estimated. These selected scenarios are assumed to represent the overall (probabilistic) distribution of events, although ideally all the flood scenarios need to be elaborated to estimate the overall risk. This approach, using selected scenarios, has its limitations, and it is clear that several improvements to it can be made. Nevertheless, even this relatively simplified model is expected to be able to provide preliminary estimates of the risk level.

In the present study, a one-dimensional (cross-sectional) approach is followed, which is judged to be sufficient to showcase the methodology proposed. A good indication of the risk can be obtained in this manner, while a more laborious two-dimensional (2D) approach would be needed for a more precise risk assessment. This 2D approach can be accomplished using the same modeling tools as used in the present research and should be the focus of future work. Below, the steps and main assumptions of the model are described in detail.

2.2 Probability of flooding

When assessing the probability of failure of a flood defense system, it is necessary to take into account the different failure mechanisms which can lead to flooding. This is especially true for the case of tsunamis, which can either overflow or breach defenses, requiring an assessment to be made of their strength against such events. For the case of Kamakura, it is assumed that overflowing will be the only failure mode, as the only flood defense system currently in place is the coastal road, which is unlikely to fail in the event of a tsunami [based on the performance of similar structures during the 2011 Tohoku event (Jayaratne et al. 2016 ; Mikami et al. 2012 )]. If the risk of the flood defense failure was to be taken into account, the hydraulic load conditions and the resistance of the structure would also have to be considered.

For this study, the load is characterized by means of one stochastic variable (tsunami height), and the resistance by a deterministic variable (height of the flood defense). The inherent uncertainties, related to the occurrence of tsunami wave heights with time, have to be described by means of stochastic distributions. To do this, historical data on tsunami heights and their return periods are necessary. Kanagawa Prefectural Government ( 2016 ) modeled all known historical tsunamis in the last ≈ 550 years (a total of 7 events) using the current bathymetry and topography of the area. Here, the incoming tsunami height is defined as the maximum water depth at the coastline before it is influenced by any of the protection measures.

Using this data, a regression analysis was conducted to approximate the return period of certain tsunami levels. The return period is inversely proportional to the probability of exceedance of tsunami height. The relationship between the approximated return period and the incoming wave heights for the different sections of the coast is then fitted with a distribution line chosen from the extreme value theory. The best-fit line is chosen based on different statistical tests and was selected to be the type 3 generalized extreme value (GEV) distribution. The distribution fitted to represent a representative tsunami level for the Kamakura coast is illustrated in Fig.  1 . The fitted distribution will be used to describe the probability of flooding for the different scenarios in Sect.  2.3 .

Distribution curve of recalculated incoming tsunami heights for different sections of Kamakura coastline for seven historical tsunamis (Headquarter for Earthquake Research 2016 ). Coastline sections are defined on the map of Kamakura in the insert

2.3 Flood scenarios

To assess the damage that can result from a tsunami, it is necessary to have an understanding of its hydraulic characteristics as it flows over land, such as inundation depth, flow velocity, run-up distance and arrival time. These were determined by different flood scenarios which were modeled in Simulating WAves till SHore (SWASH) (Zijlema et al. 2011 ). This efficient computer package is a shallow water flow model, with a pressure correction term that also enables a good representation of wave dispersion, wave-breaking behavior and flood-drying algorithms. A one-dimensional run-up model was created in SWASH, with the bathymetry of a chosen transect illustrated by the red line in Fig.  2 . The transect was important for wave development in the 1D model. However, it is worth noting that the bathymetry in Kamakura bay and topography in the coastal area are rather uniform along the shore. The hydraulic characteristics were outputted along the entire computation grid for different time steps.

Bathymetry map of coastal area near Kamakura, along with the chosen 1D transect (USGS 2016 ; GEBCO 2016 )

Another important factor in the flood scenarios is the type of wave used to model a tsunami. Two types of waves, namely a solitary wave and (crest-leading) N-wave, were considered, as these are commonly used to model tsunamis. A simple calibration for the 1D flow model was conducted based on the 2011 tsunami event around Sendai to decide which wave type to use, and it was determined that the N-wave better captures the essential features observed there. This validation is illustrated in Fig.  3 , which shows the measured envelope of inundations depths recorded in Sendai (Mori et al. 2011 ) and the inundation depths and run-ups for both types of waves, indicating that the N-wave better captures the essential characteristics.

Run-up distance and inundation depth of the solitary wave and N-wave SWASH simulations, together with the observed run-up distribution line around Sendai (Mori et al. 2011 )

For Kamakura, which has a mild-sloping seabed similar to that at Sendai, a crest-leading N-wave shape was applied to different incoming wave heights to create the flood scenarios. The flood scenarios will focus on tsunamis caused by the Sagami trough (the closest trough to Kamakura, and tsunamis caused by it are expected to have short warning times, which were considered to be the most dangerous case from the point of view of disaster risk management in the city). The wave period is taken as constant, as the subduction failure areas that can cause a tsunami were assumed to be relatively constant in size. Since the same fault is chosen as the source of the tsunami, the length scale of the tsunami can also be assumed to be rather constant across different magnitudes. Moreover, the crest of the applied (crest-leading) N-wave had a shorter duration than that of the solitary wave, so effectively the wave period was varied. Hence, if only the positive part of the N-wave will contribute to the run-up, the wave period has been effectively varied. These flood scenarios are then analyzed to understand the different flood patterns and resulting consequences.

2.4 Assessment of the consequences

2.4.1 general.

The consequences of a tsunami can be estimated based on the outputs of the flood scenarios from SWASH, and information regarding the spatial distribution of population density and land use patterns in Kamakura. These consequences were extrapolated from the 1D cross section to calculate the expected total damage to the exposed area of Kamakura and computed with a simplified version of existing damage functions for both loss of life and damage to buildings. The determining variable for the damage functions is the dv (absolute value of the product of depth d and velocity v of the water) value, where the maximum dv value in time is taken for each spatial unit in the computational grid to take into account the entire tsunami progression from landing to withdrawal. The proposed approach for estimating the loss of life and damage to buildings is briefly summarized in Sect.  2.5 . Other damage categories such as business losses, number of injuries, the losses of historical values or indirect damage were not analyzed, which essentially makes the results of the present research conservative.

2.4.2 Loss of life

The loss of life was determined following a methodology similar to that proposed in Jonkman and Penning-Rowsell ( 2008 ). Here, the method to estimate the loss of life has two main steps: estimating the exposed population and then estimating the mortality of that population. First, the exposed population for each flood scenario can be estimated by taking into account the arrival time of the tsunami and the time required for evacuation. The arrival time of the tsunami is determined from each of the flood scenarios simulated in SWASH. The time required for evacuation is estimated based on a simple evacuation model. Similar to the flood scenarios, the evacuation model is also represented in 1D, and thus, evacuation refers to a simple landward evacuation to higher grounds. For this study, the model assumes a uniform distribution of the population and only takes into account the local population and not the tourist population (again resulting in a conservative result). In the model, the time required for evacuation depends on the location of a given person along the cross section, the speed that person can evacuate at, and their evacuation behavior. The location of the people was taken from the computational grid of SWASH, and the speed of each individual took into account their age and the relative distribution of each population type (average adult, children and old/disabled) among the general population (Carey 2005 ).

Table  1 shows the percentages of people in each population type (Kanagawa Prefectural Government 2016 ) and the characteristic speed of each group. The inclusion of evacuation behavior was considered in the evacuation model, as it influences evacuation effectiveness, and this has been recognized as a big issue during the Tohoku earthquake in 2011 (Yun and Hamada 2012 ). The statistical values observed during the Tohoku event in 2011 will be used for Kamakura (presented as the initial condition in Table  2 ) to include evacuation behavior. These are split into three categories: those who evacuated immediately after receiving the tsunami warning (13% of the population), those who evacuated with a delay (60%), and those who did not evacuate at all (27%) (Yun and Hamada 2012 ). Here, optimized communication is defined as a system which disseminates the tsunami warning efficiently, through the use of devices such as mobile phones, and it is thereby assumed to improve the evacuation behavior and effectiveness. This measure will be included as a risk-reduction intervention (see Sect.  2.5 ).

The criterion for safe evacuation is given as:

Here, t evac is the time it takes for a given person to evacuate from a location, x max is the distance from the coast to safe grounds, x 0 is the distance from the coast to the location of a given person, c evac is the evacuation speed of a given person and t delay is the time delay to begin evacuation. The delay observed in the Tohoku event ranged from 5 to 60 min. This was simplified and adjusted for the case of Kamakura and was given a deterministic value of 5 min. This is approximately one fourth of the time available before the tsunami arrives. This simplified approach can be used to define which zones are safe and which parts of the population are exposed to the tsunami inundation. An example of the applied evacuation model is given in Fig.  4 .

Example of x–t diagram for the age category of children (1.2 m/s) for a 14-m tsunami flood scenario

People who start evacuation in the pink zone are expected to be caught up by the tsunami. For example, a child who is located at the coast survives if he or she starts to evacuate immediately, though another child in the same location will be caught up by the tsunami if he or she waits 5 min to start evacuating.

Second, to estimate the number of casualties among the exposed population, a mortality function that takes into account the dv criteria was also used, based on previous research on stability of people in flood flows (Jonkman and Penning-Rowsell 2008 ).

If the result of the damage function is 1, mortality is assumed to be 100% for that given location (Jonkman and Penning-Rowsell 2008 ). The estimated mortality function is combined with the exposed population at a given location in time to approximate the number of casualties resulting from each of the flood scenarios. The exposed population in the possible inundation area is approximated to be 98,349 people from the size of the SWASH computational grid, the length of the coast and the population density of Kamakura (Kanagawa Prefectural Government 2016 ).

To come to an economic assessment of the damages, this approach for estimating life loss can also be combined with the cost of human life, which is €2.1 million (¥226 million), after the value given by the Ministry of Land, Infrastructure, Transport and Tourism ( 2009 ) to evaluate civil projects.

2.4.3 Damage to buildings

The damage to buildings was determined by the methods proposed in Pistrika and Jonkman ( 2010 ). The method also uses a damage function that includes three different levels: “inundation damage,” “partial damage” and “total destruction.” The number of buildings exposed to flooding is directly determined from the run-up distance, and it is assumed that the buildings are uniformly distributed along the cross section. Similar to that of mortality, the damage function for buildings is also a function of the dv values (Pistrika and Jonkman 2010 ). This damage function was developed for wooden houses in New Orleans, and is assumed to be applicable for Kamakura as 67% of buildings are wooden (Kanagawa Prefectural Government 2016 ). The damage fraction F expresses the fraction of the value of the building that is lost.

The jump from no damage to 50% damage allows the inclusion of non-structural damage costs, such as the costs of goods and furniture inside a house. The cost of repairs is the product of the market value of a building and the percentage damage value. The market value of a building was offset as €0.28 million (¥35 million), which is the average value of a house in Kamakura (Kamakura City Office 2016 ).

2.5 Risk-reduction interventions

Various interventions are available to reduce tsunami and flood risks, ranging from offshore breakwaters, coastal or inland defenses, construction of flood proof buildings and warning and evacuation systems. The types of risk-reduction interventions that can be attempted in a given area are influenced by coastal topographic characteristics and societal demands. For the case of Kamakura, there are some limitations to the possible interventions that can be envisaged. For example, the construction of an offshore breakwater in Kamakura would be very expensive due to the nearshore bathymetry having a steep profile, and the community and local economy highly rely on tourism, meaning that coastal aesthetics need to be protected. Spatial solutions also face land planning limitations, as the city is densely built. Given these circumstances, the authors chose to analyze only the types of interventions that were considered feasible in both economic and social acceptance terms, namely heightening the road dike, and the improvement in evacuation measures. Evacuation can be facilitated through the construction of vertical evacuation buildings which aim to shorten the evacuation distance and optimized communication which aims to improve the human evacuation behavior in case of a disaster (Carlos-Arce et al. 2017 ; Takabatake et al. 2017 ).

Vertical evacuation proved extremely valuable during the Tohoku disaster in 2011 (Fraser et al. 2012 ). Due to an existing building code in Kamakura, buildings are limited to a height of 15 m (Kamakura City Office 2016 ). A reference evacuation building developed by Daiwa House ( 2015 ) requires the structure to be built in areas where the inundation depth is less than 5 m. To meet these requirements for what is expected for a 1 in 1000 year tsunami, the vertical evacuation buildings were chosen to be built 960 m inland from the coast and assumed not to have a limit to the number of individuals they could accommodate—as illustrated in Fig.  5 . The mountains are illustrated in the figure to show that in reality there are other evacuation areas or high grounds available for people. Existing evacuation buildings, as shown in the insert of Fig.  5 , were not taken into account in this paper as the location of the building was also one of the factors to be tested for risk reduction. Optimized evacuation was also very effective during the 2011 tsunami in Minamisanriku (Fraser et al. 2012 ). By optimizing communication to disseminate a tsunami warning, the evacuation behavior is assumed to improve based on engineering judgement, as illustrated in Table  2 .

Schematization of vertical evacuation buildings and their conditions

3 Results of risk quantification

3.1 probability and consequence estimates.

A variety of different tsunami scenarios can cause flooding to Kamakura. Seven different tsunami levels with incoming wave heights of 6, 8, 11, 12, 13.5, 14, 14.5 m were modeled for the flood scenarios, together with different combinations of risk-reduction interventions.

The baseline situation (also shown in Fig.  7 ) illustrates the risk for the current situation, taking into account the influence of the existing protection measures (with the 3-m-high road dike). The risk-reduction interventions were then compared with the baseline situation to assess the reduction in the potential consequences.

The return periods for the seven tsunamis scenarios considered were obtained from the exceedance curve shown in Fig.  1 , and the consequences derived from the flood scenarios presented in Table  3 . The simulated arrival time, run-up distances and propagation speeds for the tsunami levels are presented in Fig.  6 . For all scenarios, large parts of Kamakura would be affected. As all the tsunamis are simulated to originate from an earthquake along the Sagami trough, with increasing tsunami height the run-up distance becomes larger and arrival time decreases. The maximum run-up distance for the 1D run-up scenarios simulated in the present work is approximately 1.4 km. This was compared with the maximum run-up distances measured in a 2D simulation modeled using the finite difference method, and a 3D simulation modeled using the finite volume method (Ishii 2017 (Bachelor Thesis, submitted); Takabatake et al. 2017 ). Both the 2D and 3D results estimated the maximum run-up distance to be 1.58 km, showing how using a 1D model (as in the present case) does not result in a significant decrease in accuracy. The maximum run-up measured in the 1D model was also compared with the 2D tsunami model ran by the Central Disaster Management Council of Japan ( 2013 ). The maximum run-up was approximately 780-m inland for a Genroku-type tsunami with an incoming wave height of approximately 10 m, which is in between the simulated tsunamis in this study, with wave heights of 8 and 11 m (see Fig.  6 ).

Maximum run-up distances and arrival times of tsunamis of various magnitude or return period

The economic damages were also assessed, including both the loss of life and building damage, which ranged from €12.1 to €37.6 billion for incoming tsunami heights from 6 to 14.5 m, with over 90% of these total costs being the result of fatalities. The number of casualties ranged from 5280 to 16,232 people (corresponding to 5.4–16.5% of the exposed population). From these results, it is clear that in order to reduce the overall risk the number of casualties should be significantly reduced.

For the first intervention, the existing road dike of 3 m was heightened to four different heights: 4, 8, 12 and 16 m. The results showed that the damage reduction from heightening the road dike is limited, i.e., the largest risk reduction is approximately €15 billion for a 16-m dike. There is a limit to the damage reduction because overflow occurs even with the construction of large road dikes, as the simulation model employed indicated that for the case of an N-wave the incoming tsunami bore is (partially) reflected by the tsunami wall (though it is not clear how accurately the model is able to reproduce the real tsunami in this case). Moreover, the dense population of Kamakura leads to large numbers of casualties even when the inundation area is small.

For the second intervention, two different types of evacuation improvements were shown to have different advantages. Vertical evacuation buildings were observed to be effective for large-scale tsunamis as the run-up distances are larger, illustrating their value to reduce casualties. Optimized communication reduced damage costs by half, and the number of casualties by half or more depending on the flood scenarios. There is a limit to the number of casualties which can be reduced in the evacuation model used in this study, as there is still 10% of the population who are assumed not to evacuate; thus, further reduction in casualties would require improvement in evacuation behavior.

3.2 Risk quantification

Based on the information regarding the probability and consequences, a cost-benefit analysis (CBA) can be conducted, and the individual and societal risk quantified. In the Netherlands, a CBA is used as a decision-making tool for flood management to determine which solution is the most efficient (Kind 2014 ). The analysis takes into consideration the flood risk and the cost of preventive measures. The individual risk, also known as local risk, is the probability of dying due to flooding of an average, unprotected person at the site under consideration (Jonkman and Schweckendiek 2015 ). The societal risk represents the relationship between the probability of failure due to an event and the number of fatalities expected from it. This relationship is known as the FN criterion (Vrijling and van Gelder 2002 ). The results of the CBA will be presented first, followed by the results of the individual and societal risk.

3.2.1 Cost-benefit analysis

The conceptual model used to evaluate the CBA considers the total cost (TC) of the project over its lifetime as the sum of the investment ( I ) and the risk ( R ). In an optimal situation the solution involves the minimization of the TC,

The risk is computed from the probability of flooding (P f ) and the costs of loss of life ( L ) and damage to buildings ( D ). Both the investment and risk is given in terms of net present value (NPV), where the interest rate r ′ is 2.5%. This value was adjusted from the real interest rate in Japan to maximize the value of the project (de Neufville 1990 ). Investments aim to create a safer system and are compared with the reduction in the risk in the system. The investments for this study are the costs for heightening the dike and improving the evacuation system. Investments for the dike heightening include the initial costs, variable heightening costs and relocation costs (of houses due to widening of the dike). For evacuation improvements, the investments include the maintenance/operational costs for the early warning system, construction costs for the vertical evacuation building and costs of the optimized communication. A summary of these costs is given in Table  4 .

The results of the CBA can determine the optimal solution, i.e., the one that results in the lowest total cost. The annual total risk, which is the sum of the probability multiplied by its consequences, for the baseline (current) situation was €257.5 million, and the NPV risk was €10.3 billion.

The results illustrated in Fig.  7 show the relationship between the investment and the decrease in risk for each intervention, and Table  5 provides the cost-benefit ratios of some of the interventions. In Fig.  7 , the vertical distance from the baseline to each point illustrates the monetary risk reduction in that intervention, i.e., optimized communication had a risk reduction of €5.7 billion. The risk reduction in vertical evacuation is shown to be low, as the present research assumes that 27% of the population will not evacuate. Thus, changes in evacuation behavior (indicated as optimized communication) are necessary if vertical evacuation buildings are to play a major role in safeguarding the lives of local residents. This is demonstrated by the lowest risk of the considered options being the combination of evacuation interventions, illustrated by the blue cross (also, cost-benefit ratio for improved evacuation is the largest, as shown in Table  5 ).

Relationship between the risk and their investment of different risk-reduction interventions

3.2.2 Individual and societal risk

The concept of individual risk and societal risk is commonly used to assess the acceptable level of risk to life for flooding in the Netherlands (Jonkman et al. 2011 ) as an addition to the CBA when evaluating a flood defense system. It is important to note that acceptable risk levels for both individual and societal risk are not defined in Japan for tsunamis, but are computed in this study to present the existing risk levels for tsunami-prone areas.

The individual risk is computed with the following equation:

P d|f is the probability of death given a flood event and is dependent on the mortality zones, or simply a location x , which is defined as a function of the dv values used when estimating the loss of life. The individual risk for the baseline situation is computed to be 2.44 × 10 3 per year for areas close to the shore, where the expected mortality is 100%. The acceptable level of individual risk for areas in the Netherlands that are protected by flood defenses has been proposed to be 10 −5 per year (Jonkman et al. 2011 ; Vrijling et al. 1998 ).

The societal risk is concerned with the large-scale effects that a high-order event can have throughout the economic and social life of a country. The acceptable level of societal risk can be presented by the limit line. For flood risks in the Netherlands, a limit line has been proposed by Vrijling et al. ( 1998 ) called the “TAW line,” taking into account country-specific accident statistics and accepted risks in other sectors. The limit line can be shifted to take into account differences in risk acceptance and perception between various sectors. For example, risk criteria (and thus limit lines) are stricter for chemical nuclear facilities than for flood protection systems in the Netherlands. Applications and scaling of the framework to other countries have been explored, i.e., Vietnam (Van Mai 2010 ). The results for Kamakura are illustrated in Fig.  8 along with the TAW line.

FN curves for different tsunami scenarios along with the TAW line

A given situation is considered safe when the curve lies within the limit line. Thus, Fig.  8 illustrates the high-risk levels tsunamis pose and the importance of defining different acceptable risk levels for different hazards. The FN curve for tsunamis is presented to demonstrate another method of defining safety levels.

4 Discussion

4.1 general.

Results indicate that a tsunami in Kamakura can cause thousands of fatalities. The flood scenarios in this study are limited to Kamakura, but when considering the entire coastline of Sagami Bay, which includes multiple large cities, the consequence of such tsunami can be disastrous. For the scenarios simulated, the percentages of the estimated number of fatalities with respect to the exposed population are in line with the observed fatality proportions in the aftermath of the Tohoku event of 2011 (Yamao et al. 2015 ).

A large variation can be seen in the estimated number of casualties, depending on the scale of the tsunami. This is due to the large differences in the run-up distances, which are directly dependent on the size of the incoming wave height; the larger the incoming wave height, the larger the run-up distance. However, a more realistic estimation of casualties can be made by reducing the uncertainties which exist in the proposed simplified tsunami risk assessment. The evacuation model estimates the number of fatalities based on parameters such as evacuation speed, delay times and other factors which are given deterministic values. By using the probabilistic distributions for these parameters, a more realistic estimation of evacuation could be made. Also, more detailed evacuation models can be used that include the 2D road network, traffic bottlenecks and individual behavior (Lumbroso and Tagg 2011 ; Uno and Kashiyama 2008 ; Takabatake et al. 2017 ).

Other uncertainties can be associated with the selection of tsunami levels and the modeling of the flood scenarios. The tsunami levels are based on the distribution curve, and depending on the distribution curve chosen, the corresponding incoming wave height for a 1/1000 year tsunami can differ by around 10 m. Note also that in the present work the area of subduction failure was taken as constant, and as the 2011 Tohoku Earthquake showed, level 2 events can mobilize large section of the fault, even if there is no historical evidence for it. However, since extreme tsunami scenarios have a small contribution to risk, the large difference in incoming tsunami heights for less-frequent tsunamis are not weighed highly in this study. Nevertheless, the authors strongly recommend that any evacuation buildings should be designed with the most onerous wave heights in mind, and thus recommend adding at least another 10 m to the design level of these buildings as a factor of safety. The 1D run-up model is obviously also limited in its ability to provide answers for the entire city, and flood scenarios can be improved by using 2D models, which should include spatially varying hydraulic roughness. In this sense, the present paper is only a proof of concept and should be followed by a more detailed appraisal.

The optimized communication measure which was considered in this study is based on the wireless receivers which were seen to be successful in Minamisanriku (Fraser et al. 2012 ). However, this system is old-fashioned compared to a new one being proposed by the Cabinet Office, which is expected to be implemented in Japan by 2019 (Cabinet Office 2016 ). This project is called the SIP (cross-ministerial Strategic Innovation Promotion program) project and aims to incorporate applications in smart phones to improve the effectiveness of disaster warning systems for all of Japan. It is expected to be cheaper and more effective than the past systems, and thus the costs used in the paper would likely decrease (though it should be noted that using higher costs results in a conservative answer).

4.2 Choice of preliminary risk-reduction solution

In this section, the choice of a preliminary risk-reduction solution for Kamakura is discussed based on the results of the study, and assumptions are made for possible intervention demands that can be posed by different stakeholders. Determining the most favorable option is very difficult as there are presently no guidelines for the required safety level. Moreover, making the choice based on the CBA, where fatalities are the major source of costs, depends on the moral judgment on assigning an acceptable cost to the amount of fatalities in case of a tsunami.

The choice for the most favorable strategy among the options considered will be made by weighing the results of the risk assessment methods. This type of approach is conducted in the Netherlands as it is presumed to assess the safety from different perspectives (Jonkman and Schweckendiek 2015 ). Based on the CBA, the most favorable strategy is different from the one which would be chosen if the individual and societal risk were taken into account. The CBA favors the solution with the lowest total cost and the maximum cost-benefit ratio, while taking into account individual and societal risk favors the solution with the lowest risk levels.

In this study, it appeared that the costs to protect Kamakura are high, as simulations using N-waves indicate that a tsunami would still overflow floodwalls due to reflection. However, the relationship between the tsunami height, reflection and the resulting water overflow past a structure is still not well understood, and the authors will seek to clarify this phenomenon in future work. At the same time, loss of life can be significantly reduced by means of better warning. With all of these considerations in mind, the most favorable strategy among the options considered for Kamakura seems to be improving evacuation through the construction of vertical evacuation buildings and optimized communication strategies. The reduction in total cost is estimated to be €4.36 billion, and the resulting individual and societal risk are in a lower range (in the 10 −4 order of magnitude, compared to other results). The feasibility and ease of implementation of this measure is also expected to be more appealing to policymakers and local authorities than the construction of a large seawall or dike. However, the authors wish to emphasize that many simplifications and assumptions have been made in the present work, and several improvements to the methodology are possible. However, this preliminary solution and its approach are expected to help guide future more detailed assessments of possible interventions to reduce tsunami risk in Kamakura.

4.3 Options for using a risk-based approach in the tsunami flood management in Japan

The application of the risk-based approach to tsunami flood management conducted in this study illustrates that this method can present an approximation of the potential risk from tsunamis and possible risk-reduction measures, and that it is possible to carry out a tsunami risk assessment.

A tsunami risk assessment could assist the development of a risk-reduction strategy in which the most effective combination of interventions is investigated. Synergistic combinations between various interventions could be derived (protection, landfills and land use changes, emergency management), also by considering both the economic risk and risk to life. It should be noted that interventions in the areas that were affected by the 2011 tsunami have already been implemented (Esteban et al. 2015 ). Nevertheless, the approach presented in this paper could be applied for the investigation of risk-reduction strategies in other tsunami-prone areas in Japan and other countries.

Finally, an acceptable risk level for the individual and societal risk is not defined for tsunamis in Japan. This would require the adoption of the risk-based concepts and political decision making on acceptable risk levels. Thus, for these levels to be defined for tsunamis in Japan, more research must be done to understand the levels of acceptable risk defined for other hazards in Japan, such as nuclear reactors. In the current practice in Japan, a design level of tsunamis is chosen based on historical events. In many regions, coastal protection facilities are designed base on so-called Level 1 tsunami, which corresponds to tsunami which has occurred in history with a return period in the order of a hundred years or so (Sato 2015 ; Shibayama et al. 2013 ). Additionally, a level 2 tsunami is considered, which would represent an event with a return period of one in several thousand years, and evacuation plans should be designed with this event in mind. Since this design philosophy is to some degree based on the notions of probability and risk, it is recommended to further compare the two approaches (full probabilistic risk assessment vs. level 1 and 2 philosophy) in future work.

Finally, the authors want to point out that assigning an economic value of human life to fatalities does not seem common in Japan although MLIT ( 2009 ) have specified a value for civil projects. Assigning such a “value of human life” is a sensitive issue, and it is the choice of decisionmakers whether this should be done. The authors do not necessarily believe that assigning such a value is the best way. The inclusion of an economic value of human life in this paper was done for illustration purposes and to come to an assessment of the cost effectiveness of interventions. Alternatively, instead of assigning an economic value to human life, separate decision criteria could be assigned to the risk to human life, such as the individual and societal risk concepts introduced in this paper.

5 Conclusion

A risk assessment framework for tsunamis was developed, and the framework was then applied to evaluate a case study of the city of Kamakura. The results indicate that a tsunami event in this area can expose over half of the total population of Kamakura to flooding, resulting in thousands of casualties. For all tsunami levels which have been simulated, 90% of total damage costs are a result of fatalities. Based on the quantitative analysis of the flood risk, the results indicate that the cost-benefit ratio is maximized and the societal risk levels are low, in other words closer to the TAW line rather than that of the baseline condition, for evacuation improvements. The dike heightening intervention had a limit to the reduction in risk it could accomplish. This flood risk assessment for tsunamis can be applicable to other tsunami-prone areas.

The results presented are based on a simplified framework for flood risk assessment. For a more elaborate risk assessment, improvements can be made to each step. The most important step in the framework is the determination of the tsunami return period, including the use of bootstrapping methods in the fit of the tsunami exceedance curve. This influences all of the following steps in the framework and is also the most difficult to determine. A more complete assessment of the various earthquakes for multiple troughs, locations and magnitudes is recommended to come to a more complete characterization of the range and return periods of possible tsunami waves at Kamakura. Further improvement can be made in this step by employing a 2D approach in flood modeling and evacuation modeling, with the inclusion of spatially distributed data. 2D simulations for the tsunami run-up would highly improve the accuracy of the flood mapping, thus resulting in a better approximation of the potential consequences. Another improvement would be to add parametric dependencies among different variables such as earthquake magnitude and deflection height. These improvements can be made to reduce the uncertainty which exists in this step. Nevertheless, the framework developed aims to give a first approximation for risk-reducing design.

Based on these results, further investigation of the possibilities for risk-reduction interventions for Kamakura is recommended to prepare for possible future tsunamis. The results also indicate that improvements to the evacuation measures should be recommended over hard structures such as sea walls and dikes. Therefore, information regarding the structural safety and elevation of evacuation areas, and the space available at these areas will be of importance in more elaborate studies.

For a more complete evaluation of tsunami risk in Kamakura, improvements need to be made not only for the determination of the tsunami return period, but also in the assessment of the consequences. The population at risk in this study only considers the local population, though the large number of tourists present could also influence the results. Moreover, the population and housing distribution is assumed to be uniform. In reality, however, the houses are more densely built near the coast, which could result in a larger number of casualties; thus, improvements in spatial distributions can be expected to produce more accurate results. Finally, the evacuation model uses deterministic values to portray human behavior. The model can be improved by obtaining realistic calibrated values variables, such as the evacuation behavior. Overall, the results indicate the necessity for further discussion on how to reduce the risk or vulnerability of a tsunami-prone city. The results presented in this study aim to provide the input information to discuss improvements in the tsunami risk management.

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Non Okumura, Sebastiaan N. Jonkman & Bas Hofland

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Okumura, N., Jonkman, S.N., Esteban, M. et al. A method for tsunami risk assessment: a case study for Kamakura, Japan. Nat Hazards 88 , 1451–1472 (2017). https://doi.org/10.1007/s11069-017-2928-x

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Received : 16 January 2017

Accepted : 15 May 2017

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Issue Date : September 2017

DOI : https://doi.org/10.1007/s11069-017-2928-x

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