Tsunami
The word tsunami (pronounced tsu-NAH-mee) is Japanese; it is derived from tsu,
which means harbor, and nami, which means wave. A tsunami is a series of huge
waves. It washes against the coast several times with great speed and force.

How are tsunamis caused?
Sometimes an underwater earthquake
causes a huge displacement of water
which can generate a tsunami. These
giant waves travel thousands of miles
across the sea. Not only earthquakes
but also landslides, volcanic eruptions,
explosions, and even the impact ofcosmic bodies, such as meteorites, cangenerate tsunamis.

1.Th e up h eaval/sub sid en ce of seaw aterb y an earth q uake

2. Th e g ian t w aves travel across th e sea→Tsunam is hit the coasts.

earth q u ake（source Japan Meteorological Agency website）

Difference between tsunamis and ocean waves
Tsunamis occur as a result of themovement of a huge volume ofseawater from the seabed to the sea
surface, whereas ocean waves arecaused by the movement of wind overthe sea surface. Tide embankments canprotect us from ocean waves, but are
sometimes overwhelmed by tsunamis.

Tsunami speed

ocean w ave

w ave h eig h t
sea leveltsu n am i

tsu n am i h eig h t

sea level（source Okamura, M. ”Nankai jishin ni sonaeru”）

Tsunami speed changes with the depthof the sea. An underwater earthquake at
a depth of 5,000m can generate atsunami of speeds up to 800km/h. As atsunami comes closer to the coast, its
speed and wavelength decrease, but its
height increases.
（source Japan Meteorological Agency website）

Landforms increase tsunami height
There are many different types of coasts.
We usually enjoy calm seas, but they canbe very dangerous when a tsunami occurs.
The height of a tsunami increases overtime as it gathers increasingly hugeamounts of water and carries it to theinner parts of a bay. In the case of acomplex shaped bay, this changes inaccordance with each village location. On
certain occasions in the past, the tsunamis
have been higher than predict.

1. U-shaped bay

2. cape

3. Y-shaped bay

Surviving tsunamis★Run toward higher ground

immediately!!
If you experience a major
earthquake or one that lasts longer
than a minute or if you hear theapproach of a tsunami, immediately
evacuate the coastal area and moveinland and or to higher ground. Do
not try to escape by moving along
the coast because you are not safe
from a tsunami unless you are inland
or on higher ground.

＊Some houses and buildings have collapsed becauseof powerful tsunamis.

★Ask a geopark tour guideHazard maps have been prepared for natural disasters
in Japan. Get these maps and ask your geopark tourguide, also called a geoguide at our park, about themaps, information on tsunamis, the nearest safe placesin the geopark and the previous disasters there. We
look forward to seeing you at our geopark.

★Tsunami-ten-den-ko
The saying originates from theSanriku region. It urges you to fleeby yourself without pausing to think,when a tsunami occurs. You have notime to go back home if you hear atsunami coming. Evacuate fromareas near the coast immediately, andstay away from them for some time
because a tsunami hits the coast
several times.

Earth Communication Group
Japanese Geoparks Network