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Teaching resources

Tectonic activity and hazardsPreparedness and mitigation

The Tokyo metropolitan area underground water discharge tunnel ©DDeco

Part II: Research, engineering and preparedness in Japan

Teaching resources: Tectonic activity and hazards

Pioneer in disaster preparednessJapan is recognised as a world leader and innovator in disaster preparedness and mitigation. It is arguably the most earthquake and tsunami-ready country in the world. The nation lives in a state of constant readiness for good reason: they are exposed to a fifth of the world’s strongest earthquakes.

Japan has learnt hard lessons from its history of natural hazards and plans well. It researches and innovates in state of the art technologies to improve forecasting and safeguards.

The developed economy allows it to spend billions to minimise the impact of natural hazard events on communities and infrastructure. It has the world’s densest seismometer network, the most extensive tsunami barriers and early warning systems to show for it. Earthquake forecasting has had its successes.

These efforts undoubtedly save many lives and reduce the damage to the economy and infrastructure when disaster strikes. Japan is mostly able to avoid widespread destruction and rapidly able to bounce back.

Measures to reduce vulnerability and loss

How do earthquake mitigation measures reduce vulnerability and loss?

Preparedness and mitigation measuresModify Event Human vulnerability Loss © MSFEarthquakes Not

possibleAseismic buildingsGround shaking and liquefaction mappingEarthquake education and drillsFire protectionEmergency servicesBut prediction not possible

Includes immediate rescue efforts followed by relief efforts (food, water, sanitation)Insurance, which people are urged to take out in MEDCs, while expensive, can support recoveryLong-term reconstructionTsunami Coastal

defencesEngineering

Coastal zone and land-use planningSea walls and water discharge tunnelHazard mapsSafety guidelinesEvacuation proceduresEmergency kits, food supplies and sheltersWarning and prediction systems

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Aseismic buildings Japan is world leader in terms of number of quake-resistant structures. Where possible, sensitive buildings are relocated to safer areas and, where construction or use cannot be avoided, low-use facilities are set in place.

Where construction cannot be avoided in areas recognised as at risk of liquefaction, there can be remediation of buildings on site. Most buildings have been built under major Japanese seismic codes (1981, 1987) or have been influenced in the past by seismic codes and earthquakes.

Making a building earthquake-resistant adds around 10 to 20 percent to building costs. The cost of retrofitting buildings and other structures with shock absorbers and other such devices and cross-bracing them depends on the seismic solutions for varying constructions.

In the diagram, the bracing system is working with a base isolation system. Seismic safeguards within the foundations are designed to work alongside the diagonal bracing. The diagonal bracing is working with a concrete structure.

Tokyo-Yokohama urban area Urban areas and growing cities are prioritised in risk assessment and risk reduction. Urbanisation is a critical factor in disaster risk, affecting susceptibility, coping capacity and adaptive capacity. Japan is urbanised. Its capital, Tokyo is the largest city in the world.

Three-quarters of 126 million people live in sprawling, coastal cities. Good economic provision, services and infrastructure mitigate urban risk.

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© Kakidai, Wikipedia Commons


The Tokyo-Yokohama urban area, the world’s largest city with 38 million inhabitants and exceptional urban planning and infrastructure, and one of the world’s richest cities, is a resilient city.

Though being named the second-most exposed city in the world to natural disasters by the international insurer Llyod’s of London, Tokyo is well prepared. Eighty-seven percent of buildings in the city, including skyscrapers, are reportedly built to withstand earthquakes.

Two examples to highlight the level of resources an MEDC like Japan can devote to disaster preparedness: It took 100 engineers, architect and planner to create an earthquake-proof design for the tallest structure in Japan, the Tokyo Skytree, a towering 634 m structure.

An innovative, cavernous water discharge tunnel on the outskirts of Tokyo is designed to catch flood water from tsunami or cyclones, then safely redistribute it piecemeal into the nearby Edo River. The 6 km long, five-story high underground complex cost nearly US$3 billion, an astronomical sum in its own right – even when not seen from Haiti’s perspective, where 60% of the population subsists on US$2.41 per day, under the national poverty line.

Mapping high-risk areasRisk maps play an important role in how scientists think about and display earthquake risk. Earthquake risk can be determined by locating where faults are active, where past earthquakes have occurred, and where most damage was caused. This information on fault location and history, combined with type of soil or rock and modern deformation of the sea floor, informs hazard maps.

Historic records of earthquakes can be incomplete and some countries, including Japan, have longer records than others. Where there are no records of earthquakes, geological and soil maps can be used to identify past earthquake activity. The geological, when understood, can enable high-risk areas to be mapped.

Japan has far more historical data than most regions of the world. For those that have very little data, like Haiti, it is even harder to judge earthquake patterns.

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©temblor.net


For example, the precedent for the Tohoku earthquake was recorded when an earthquake

in July 869 followed by a tsunami flooded the plains of northeast Japan.

This can aid coastal zone and land-use planning. Once hazard maps have permitted seismic zoning maps, the land use of the most hazardous areas can be regulated. Buildings such as schools and hospitals should be built in areas that are at lower risk. It is also important to ensure that there are open spaces for safety away from fires and aftershocks.

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Disaster education

Disaster education is ingrained in Japanese culture and schooling, and residents of Japan are very aware of their vulnerability in this volcanically active country regularly beset by typhoons. Japan observes Disaster Prevention Day, and communities are informed through awareness and education programmes.

Risk awareness and education mean that more people can evacuate to safety in case of a tsunami when they get an early warning. People live in a constant state of readiness, and many households always have an emergency kit prepared. Also, rather than descending into chaos and violence, long queues of people for food and facilities show the value of having educated residents about how to act in crisis.

Disaster plans and emergency servicesHaving been reminded by the Tōhoku earthquake of just how important looking at records over thousands, not hundreds of years and tsunami geology is after the, Japan is now heavily investing in understanding its tsunami history. Global experts are searching its coastlines for evidence of ancient waves, while researchers are developing new models to better understand the speed and wave height of tsunamis and the magnitude of the earthquakes that caused them.

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©World bank

©Halowand


Tsunami hazard maps can show disaster risks and evacuation routes, so can be used in tsunami evacuation maps and drills.

Disaster plans, communication and coordination need to be in place. The pioneer in crisis management, Japan has developed a comprehensive plan for preparing against disasters, which includes the Central Council for Accident Prevention chaired by prime minister, a set of cohesive rules for immediate response, an advanced research system, and extensive public training in disaster response.

Japanese national and local authorities have disaster management plans, including insurance, in place. Japan is well positioned to sustain development regardless of natural disaster. The government enforces land-use zoning and building regulations, implement evacuation drills, and set up emergency service provision.

Tools for search and rescue need to be available. Planning and organisation of services need to be in place, heavy lifting equipment available, and first aid training for many people up to date. Ordinary people need to be able to fight fire.

Fire prevention

Smart meters can cut off gas when an earthquake above a certain magnitude occurs. Seismic information is transferred to networks from gas companies instructing employees where to turn off major pipelines.

Sea walls, breakwaters and other structures Pummelled by a tsunami about every seven years, and with 35,000 km

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Tokyo Life Learning Centre disaster prevention tour and simulated disaster experience ©Go Tokyo

©Yasu


(22,000 miles) of coastline, Japan has invested heavily and is proposing more giant sea walls.

Japan has lined the areas it considers most at risk with concrete sea walls, breakwaters or other structures intended to protect the country against high waves, typhoons and tsunamis. However, evidence of their effectiveness is mixed.

At the mouth of Kamaishi Bay on the northeast coast stands the a 20-metre-thick barrier, which is 2 km long. It rises to 8 metres above the water and is anchored to the sea floor 63 metres down and Completed in 2008 after 30 years, it cost of more than US$ 1.4 billion.

Early warning systems

Before precise instruments existed, villagers erected stone markers along hillsides to alert others to how high the water could sweep inlands. This stone slab from centuries past urged residents to build on higher grounds residents. They were placed at the height tsunamis had reached in the past.

Launched in 2007, Japan’s Earthquake Early Warning (EEW) system is the most extensive in the world. It consists of earthquake detection and warning dissemination. These include:

Risk knowledge: hazards known? Patterns and trends? Risk maps and maps available?

Monitoring and warning service: right parameters monitored? Sound scientific basis for forecasts?

Dissemination: do warnings reach all at risk? Do people understand them?

Response capability: response plans up to date? Are people prepared and ready to react to warnings?

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©T.Kishimoto


Different types of earthquake warning systemsThere are different types of earthquake warning systems: S-wave-based ones as in Mexico, and P-wave-based ones as in Japan. Seismic waves travel in all directions away from the source.

P-waves and S-wavesP-waves are body waves with a push–pull action that move about 20 times the speed of sound through the crust. They are longitudinal waves and can travel through solids and liquids. S-waves are secondary waves with an up-and-down motion (transverse) that move at half the speed of P-waves and carry most of the shaking. S-waves only travel through solids.

©IRIS

Japan’s P-wave systemJapan’s P-wave system includes more than 1,000 seismometers, which are instruments designed to detect and record earthquakes.

The system calculates the earthquake’s epicentre location and magnitude, and a network of seismic intensity meters is used to predict the damage radius and maximum expected seismic intensities at each affected region.

© Japan Meteorological Agency

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Shindo seismic intensity scaleJapan uses the 10-degree Japanese Shindo seismic intensity scale, which describes the degree of shaking at a specific location, taking into account amplitude, frequency and duration of seismic motion.

An earthquake alert warning and updates are issued to the general public if a seismic intensity of 5-lower or greater has been detected by at least two seismograph stations.

Modelling tsunami wavesTsunamis, and especially their attributes, cannot be predicted with certainty. But an early warning system can model tsunami waves based on magnitude and location. Forecasts of wave size and arrival times are included in the early warning.

Deep-ocean Assessment and Reporting of Tsunami (DART)The Deep-ocean Assessment and Reporting of Tsunami (DART) graphic show how tsunami buoys work. Bottom pressure sensors attached to buoys constantly measure the pressure of the overlying water column.

If two or more P-waves are detected by two or more seismographs, Japan Meteorological Agency immediately analyses the readings and, before the arrival of the S-waves, can distribute warning information to advanced users such as broadcasting and phone companies.

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©NOAA


Limitation of early warningThe limitation of EEW is that it cannot warn before an earthquake gets set in motion. However, a lead time can allow for actions that can save lives and prevent injuries, especially if the earthquake is followed by a tsunami.

The blind zone (the shaded region within the zero-second contour in the map to the left) is where the proximity to the epicentre leaves no time for warning.

As soon as initial seismic waves are detected, the population can be alerted, and trains, lifts, factory lines and all sorts of work and process can be suspended.

In the case of the Tohoku (2011) earthquake and tsunami, seconds before the main quake struck, 27 bullet trains in use in Japan hit the emergency brakes. There were no

injuries or deaths.


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How well prepared is Japan?

Japan is extremely well prepared thanks to investing heavily in research, education, and implementing mitigation strategies, but even for one of the world’s wealthiest and best prepared nations, there are limits to how much risk and vulnerability can be reduced in the face of a megadisater.

Support from international actors such as Médecins Sans Frontières/Doctors Without Border (MSF) tends to be needed immediately after a severe natural disaster in more and less economically developed countries alike.

The earthquake and tsunamis in 2011 initially overwhelmed Japan, but the drop in the quality of life in Japan and its duration was less, and the speed of recovery was faster, than in a poor country such as Haiti.

AcknowledgementsMSF London, and especially the author Severa von Wentzel, would like to thank Mary Doherty for her expert guidance and generous support.

Further information

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