To save your life from Tsunamis

To save your life from tsunamis, evacuate immediately

  • if you feel strong shaking or weak but long-lasting ground motion, or
  • if you notice a tsunami warning, even though you don't feel shaking.

Be sure to evacuate if you feel shaking.

Points to save your life from tsunamis

On March 11, 2011, a magnitude 9.0 earthquake, the largest in Japan's history, later named the 2011 Tohoku-Pacific Ocean Earthquake, occurred off the Sanriku coast. The earthquake triggered large tsunamis that caused devastating damage to the Pacific coast of the Tohoku and Kanto regions, including Iwate, Miyagi, Fukushima, Ibaraki, and Chiba prefectures.

No one knows when or where earthquakes and tsunamis will occur. If you are at a place where a tsunami is about to arrive, you must run to high ground as soon as possible. Make sure to check the following points to save your life from a tsunami.

つなみのときのこうどうひょう
Evacuate if Take these actions After those actions
A major tsunami warning or a tsunami warning is issued (even though you don't feel shaking) Evacuate from coastal or river areas immediately to a safer place, such as high ground.
It should be noted that an area outside inundated hazardous areas may still be flooded because tsunamis vary in scale.
Get the latest information from the radio, TV, disaster administrative radio of the city, etc.
Because tsunamis will arrive repeatedly, be sure to keep away from the coast until tsunami warnings/advisories are called off.
You feel a strong earthquake or long-lasting ground shaking Evacuate from coastal or river areas immediately to a safer place, such as high ground.
It should be noted that an area outside inundated hazardous areas may still be flooded because tsunamis vary in scale.
Get the latest information from the radio, TV, disaster administrative radio of the city, etc.
Because tsunamis will arrive repeatedly, be sure to keep away from the coast until tsunami warnings/advisories are called off.
Evacuation instructions/advisories are issued from the city Evacuate from coastal or river areas immediately to a safer place, such as high ground.
It should be noted that an area outside inundated hazardous areas may still be flooded because tsunamis vary in scale.
Get the latest information from the radio, TV, disaster administrative radio of the city, etc.
Because tsunamis will arrive repeatedly, be sure to keep away from the coast until tsunami warnings/advisories are called off.
A tsunami advisory is issued (even though you don't feel shaking) Stop surf fishing or swimming in the sea and evacuate quickly to a safer place on land. Get the latest information from the radio, TV, disaster administrative radio of the city, etc.
Because tsunamis will arrive repeatedly, be sure to keep away from the coast until tsunami warnings/advisories are called off.

Major tsunami warning, tsunami warning, and tsunami advisory

A major tsunami warning, tsunami warning, and tsunami advisory contain the most important information to consider when deciding whether or not to evacuate.

The Japan Meteorological Agency (JMA) has revised the "estimated maximum tsunami heights" from 8 to 5 levels, with consideration given to the potential resultant damages and error risk of high tsunamis.

津波警報・注意報の種類
Category Indication Estimated maximum tsunami heights
Quantitative
expression
Estimated maximum tsunami heights
Qualitative
expression
Expected damages and actions to be taken
Major Tsunami Warning Tsunami height is expected to be greater than 3 meters. over 10 meter
10 meter
5 meter
Huge Wooden structures are expected to be completely destroyed and/or washed away; anybody exposed will be caught in tsunami currents.
Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.
Tsunami Warning Tsunami height is expected to be up to 3 meters. 3 meter High Tsunami waves will hit, causing damage to low-lying areas. Buildings will be flooded and anybody exposed will be caught in tsunami currents.
Evacuate from coastal or river areas immediately to safer places such as high ground or a tsunami evacuation building.
Tsunami Advisory Tsunami height is expected to be up to 1 meter. 1 meter N/A Anybody exposed will be caught in strong tsunami currents in the sea. Fish farming facilities will be washed away and small vessels may capsize.
Get out of the water and leave coastal areas immediately.

Note

Tsunamis may hit before warnings are issued if the source region is near the coast. Be sure to evacuate when strong shaking or weak ground motion continuing for an extended period occurs.

If a Major Tsunami Warning with the quantitative term "Huge" is issued, tsunamis as large as those seen after the Great East Japan Earthquake of 2011 may hit. Evacuate immediately to the safest place possible.

Tsunami heights may exceed estimates due to coastal topography and other factors in some regions. Do not assume you are in a safe place; keep evacuating to higher and higher ground wherever possible.

Tsunami waves are expected to hit repeatedly. Do not leave the tsunami evacuation location until Tsunami Warnings are cleared.

Tsunami-tendenko

Inhabitants of the Sanriku area, who have repeatedly suffered from tsunamis, have handed down from generation to generation a tsunami-tendenko maxim: when a large earthquake or tsunami occurs, individuals should run for high ground to save their own lives rather than delay evacuation trying to help family members or gathering possessions. This tsunami-tendenko is not an egoistic, selfish action but rather a call for individuals to evacuate using sound judgment. In other words, individuals must not go to look for blood relations but evacuate as soon as possible on the premise that they trust one another. In the Great East Japan Earthquake, there were instances where people quickly evacuated, adhering to the tsunami-tendenko teaching they had been told by their families, resulting in parents and children in different places evacuating separately. To take such successful evacuation action, you must understand that your life will be endangered in a tsunami disaster if you try to check family members' safety. It is also advisable to make preparations with your family beforehand regarding what actions to take to save individual lives in cases of emergency. (Quoted from "The present state of Meteorological Service in 2012," edited by JMA)

Understanding tsunamis

What is a tsunami?

While a wave is the motion of water on the sea surface caused by the wind, a tsunami is generated by seaquake movement on the seafloor and possesses great energy because all of the seawater from the sea bottom to the surface moves. A tsunami rolling through the coast travels to land while keeping its height and destructive power and continues up rivers.

Features of tsunamis

Breakneck speed equivalent to a jet plane in the deep sea

The speed of a tsunami relates to the depth of the sea. If a seaquake occurs at a depth of 5000 m, the resultant tsunami reaches a speed of about 800 km/h, which is equivalent to the speed of a jet plane. The speed slows down as the depth of water decreases; the speed near the coast at a depth of 10 m will be about 36 km/h, which is still equivalent to the speed of an Olympic sprinter.

Tsunamis occur repeatedly

After the first tsunami, further tsunamis will arrive. The first is not necessarily the highest. In the case of the Great East Japan Earthquake, the later tsunamis were the highest.

Wave height may exceed 20 m

Wave height (the height of a tsunami) greatly depends on the geographical features of the coast. As water becomes shallow, a tsunami becomes higher. In the Great East Japan Earthquake, a run-up height of 39.7 meter was recorded locally at Ryori Bay in Ohfunato City, Iwate.

Tsunamis can arrive from the other side of the earth

Distant tsunamis cross the Pacific Ocean and reach Japan from countries as far away as Peru or Chile. It takes tsunamis more than 20 hours to reach Japan. After the first tsunami arrives, the later tsunamis arrive one after another.

Tsunamis are not felt in the offing

Because the wavelength of a tsunami in the offing is very long, ranging from 10 km to 100 km, it is difficult to recognize the movement of seawater as part of a tsunami. So, if there is enough time until a tsunami arrives, fishermen sail their fishing vessels out to the offing and can avoid damage to their fishing vessels.

Terrifying destructive power of tsunamis

Tsunamis with terrifying destructive power swallow up people and buildings. Waves advancing on land and returning to sea are both very powerful-and this occurs repeatedly. Apart from the coast, due caution is required on river basins as well. In the Great East Japan Earthquake, tsunamis travelled 15 km up the Kitakami River in Miyagi.

Tsunami disaster in Hitachinaka City

The earthquakes and resultant tsunamis of the Great East Japan Earthquake greatly affected Hitachinaka City. The Oarai massive tsunami observation monitor recorded a maximum height of 4.0 meter of the tsunamis, and about 500 buildings in the coastal area of the Nakaminato district were flooded above or below the floorboards.

It is also reported that before the Great East Japan Earthquake, earthquakes and resultant tsunamis that occurred off the coast of the Boso Peninsula in 1677 (Enpo 5 in the Japanese Imperial era) generated 2-7 meter tsunamis off the coastal area of Ibaraki.

March 11
14:46 The 2011 Tohoku-Pacific Ocean Earthquake occurred (a weak 6 on the Japanese seismic scale in Hitachinaka City).
14:49 A tsunami warning was issued (announced by disaster administrative radio).
15:08 Evacuation instructions were issued (announced by disaster administrative radio).
15:14 A major tsunami warning was issued (announced by disaster administrative radio) Note: the announcement was made intermittently after the warning was issued.
15:17 The first tsunami wave (1.7 meter) was recorded.
16:52 The maximum tsunami wave (4.0 meter) was recorded.
March 12
13:50 The major tsunami warning was downgraded to a tsunami warning.
20:20 The tsunami warning was downgraded to a tsunami advisory.
March 13
17:58 The tsunami advisory was called off.

The tsunami warnings lasted for about 30 hours in the Great East Japan Earthquake. Be sure to keep away from coastal areas until tsunami warnings/advisories are called off.

Advance preparations

To prevent people from panicking when a tsunami approaches, prepare in advance by checking evacuation sites and routes. Since family members are not necessarily together, check and decide beforehand where to evacuate and how to contact one another.

Points to be checked in advance

Get information about tsunamis from the radio

After tsunamis are generated, the situation will change from moment to moment. Get the latest information from the radio, TV, disaster administrative radio of the city, etc., and act in safety.

Talk with your family in advance

Talk with your family in advance about where to evacuate and how to contact one another if tsunamis occur. There are many points to be checked in advance with your family. Are there designated evacuation sites or high ground near your home? Can several different routes be used for evacuation to such places? How long does it take to walk from the place you are likely to be to higher ground?

Take part in emergency drills

Take part in emergency drills conducted in the community, and check for potential dangerous places on evacuation routes and detours. Some volunteer disaster management organizations in communities call on inhabitants for participation in drills. Such drills are a good opportunity to know the response capacity of your surroundings during disasters.

Prepare emergency kit items in advance

Prepare minimal necessary items for emergencies and keep all the items together in an easily accessible place that can be reached immediately. You have to evacuate quickly from tsunamis. Never fail to evacuate by minding valuables.

Multifunctional mobile phones

Mobile phones can be used not only for talking but also for web browsing and texting. Some models can automatically receive disaster-related information, such as tsunami warnings and earthquake early warnings; some can receive radio and TV broadcasts; and others are equipped with useful functions, such as lights and beepers. Check the available functions of your mobile phone in advance.

Portable radio, which is helpful in disaster situations

If you have a radio receiver, you can easily get information through it. Portable radio receivers were very useful in past disaster situations because they are easy to carry, do not require much battery power, and enable you to listen while you take action. Have at least one radio receiver ready in each home for an emergency.

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更新日:2017年02月01日