Are you prepared fordisasters?
2. Tsunami
Tsunami waves may strike after an earthquake. If you feel strong shaking and are in or near the coast, evacuate
immediately to high ground or another safe place. Tsunami waves may strike repeatedly with high speed, and thefirst wave is not necessarily the biggest. Do not go near the sea until the tsunami warning or advisory is lifted.

Why do tsunami occur?
- What is a tsunami?
When a large earthquake occurs at a shallow
depth below the seafloor, the resulting fault
movement causes the seafloor to rise or subside.
This in turn causes massive amounts of water tomove up and down, and this movement spreads
out in all directions in the ocean. This is how atsunami is generated.
Tsunami have a longer wavelength than normal
ocean waves. As they lose little energy in theirmotion, they travel further.

Tsunami generation

Topographic changes
in the seafloor

Source area

Tsunami waves propagate more slowly as the sea
becomes shallower. As a result, trailing waves
catch up with those ahead nearer the coast, andthe tsunami grows much higher. Coastal
landforms and buildings can also cause wave
reflection and diffraction, thereby amplifying
tsunami heights in some areas.
Tsunami may run up from the waterfront toinland areas depending on coastal landforms.
These waves contain massive amounts of water
welling up from the seafloor to the surface; they
can run ashore with huge power and wash away
everything in their path, destroying buildings
and carrying inland large ships, rocks and otherobjects, which themselves can further damage
houses and buildings. Tsunami can also run up
rivers and cause damage to basin areas.
- Tsunami speed
Tsunami waves travel faster through deep waterand more slowly as they reach shallower coastal
areas. As a result, trailing waves catch up withthose ahead nearer the coast, and the tsunami
grows much higher.

Run-upheightNormal sea level

Wat er dept h
5, 000 m

800 k m/ h

Wat er dept h
500 m
Wat er d ept h
100 m

250 k m/ h

Wat er dept h
10 m

110 k m/ h

36 k m/ hTsunami damage
The greatest damage caused by the 1993 Hokkaido Nansei-oki Earthquake resulted from a tsunami that struck
shortly after the tremor. Waves higher than 3 meters hit all coastal areas of Okushiri Island near the epicenter off thecoast of Hokkaido immediately after the quake, and waves measuring over 10 meters were also observed in many
areas. The event caused extensive damage and many casualties.

More recently, the 2003 Tokachi-oki Earthquake triggered tsunami waves as high as 2.55 meters at Tokachi Port andover 4 meters in coastal areas in the towns of Taiki and Akkeshi. The tsunami also ran 11 kilometers up the TokachiRiver.

Japanese people are all too familiar with tsunami-related disasters.

Tsunami countermeasures
If you are in or near the coast
Leave the area immediately and evacuate to high ground or another safe place if strong shaking or weak but
long-lasting slow shaking is felt.

Get reliable information
Get information from TV, radio and/or other official channels; do not act on hearsay or rumors. Stay away from thesea until the tsunami warning or advisory is lifted.
A t suna m i w ar ningha s bee n issu ed. ”Tsunamiadvisory

Tips to protect yourself from a tsunami
1. Leave coastal areas immediately and evacuate to a safe place if strong shaking (seismic intensity of 4 orgreater) or weak but long-lasting slow shaking is felt.
2. Even if you do not feel shaking, leave coastal areas immediately and evacuate to a safe place if a tsunami warning isGeneralissued.
public 3. Get reliable information from TV, radio, municipal information cars and/or other official channels.
4. Do not approach the seashore to engage in bathing or fishing activities when a tsunami advisory or tsunami warning
is in effect.
5. Remain on alert until the warning or advisory is lifted, as tsunami waves may strike repeatedly.
1. Evacuate from the port (*Notes 1 and 2) immediately if strong shaking (seismic intensity of 4 or greater)or weak but long-lasting slow shaking is felt.
2. Even if you do not feel shaking, evacuate from the port (*Notes 1 and 2) immediately if a tsunami

warning or advisory is issued.

Ships

3. Get reliable information from TV, radio and/or other official channels.
4. Small ships that cannot evacuate from the port (*Note 2) should be pulled up to high ground and lashed;

if this is not practical, the best possible action under the circumstances should be taken.
5. Remain on alert until the warning or advisory is lifted, as tsunami waves may strike repeatedly.
*Note 1: from the port: to deeper, broader waters*Note 2: Evacuation from the port, pulling up of small ships and other measures should be taken only when there is time to do sobefore a tsunami strikes.