Natural disasters

Tsunami

Summary of a tsunami

A tsunami is generated by the up-down motion of seawater around the area where an uplift or subsidence of the seabed is caused by a submarine earthquake, or when a submarine landslide occurs. The greater the up-down motion of the water surface, the greater the destructive power of the tsunami when it reaches the coast.

The tsunami waves involve leading waves and backwashes that continue for a period of time.
The tsunami wave that propagates offshore and heads to the coast is called the leading wave while the tsunami that propagates from the coast and heads out to sea is called the backwash.

Whether the beginning of the tsunami wave (the first wave) is a leading wave or a backwash depends on the direction and the magnitude of the faulting in the area where the tsunami occurs. It is also affected by the submarine topography of the area around which the tsunami reaches.

When the backwash comes first, the water rolls down the coast offshore and the sea bed (which is not normally seen) appears. If people approach the coast without knowing that this phenomenon is caused by the tsunami, there is a danger that they will be swept out to sea by the leading tsunami wave that follows the backwash.

Being prepared for tsunami
Take great caution even during small tremors.

Even small tremors can lead to a massive tsunami.

Evacuate to higher ground.

Evacuate to the HIGHEST POSSIBLE PLACE, not to the farthest possible place from the coast.

The speed of tsunami waves is fast!

A tsunami may come before the tsunami warning or advisory is issued. Immediately evacuate when you sense an earthquake.

Tsunami waves come repeatedly.

Tsunami waves can come once, twice or more times. Caution is needed until the waves calm down.

Take caution even if there is no backwash.

Due to the topography around the seismic hypocenter, backwashes do not occur with some tsunamis.

Take caution when it is high tide.

The high water level can cause significant tsunami damage.

Listen to accurate information.

Listen to the disaster management radio broadcasting, and public TV and radio announcements to obtain accurate information.

Keep away from rivers.

Tsunamis run up rivers. Be sure to keep away from rivers.

Keep away from the coast.

Be sure to keep away from the coast until the tsunami warning or advisory is cancelled.

At sea

When at sea, immediately take action according to wireless information, etc.

Click here for the tsunami information video.

Summary of natural disasters

Guide to the smart phone site

Click here for further information

Related links

Disaster information from the Ministry of Land, Infrastructure, Transport and Tourism of Japan

List of multilingual medical institutions Sendai International Relations Association

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