[sound of waves crashing]
In the Sea of Japan there is a small island whose name is Okushiri. On the southern tip
of this island there is a small village by the name of Aonae. All of these homes were
present before July 12, 1993.
And one can look at the monument that stands up in the center of your screen as a marker.
10 o'clock at night on July 12 a magnitude 7.6 earthquake occurred that produced 1 hour
of tsunami attacks followed by intense fires.
These pictures were taken moments after the tsunami had destroyed most of the village
and the fires that are raging are the effects of such a tsunami disaster.
Oftentimes people do not consider that tsunamis, which basically flood the coastline, can also
start fires. But in fact, for this particular event, the fire did the most damage to the
community of Aonae.
[sounds of fire]
Now we are looking at the breakwater that was supposed to protect this village. It has
been breached by the weight of the tsunami during the 1 hour of attacks that occurred
the evening before.
Examine all of the debris in the water and those are the remnants of the homes that we saw
prior to this tsunami in July of 1993.
We are now looking at the waterfront area which the weight of the water crushed many
of the homes and many of the buildings that were along the waterfront.
But in addition to the weight of the water by the tsunami, floating debris, such as large
fishing vessels, also crashed into these buildings, and as a result of this weight of the water
plus the debris in the water, it had the effect of demolishing everything in its path.
In this over flight of the southern tip of Okushiri Island shows the devastating effect
of these waves. Notice all the brown debris in the water are the remnants of the 500 homes
that were on this tip. And now it's only a sheet of sand with a scattering of fishing
boats that tell us what happened here. There is the monument that we saw earlier.
How could such a disaster occur, what are the processes of Earth that could create such
a disaster?
The Earth could be considered a large hot ball of molten lava and the top of this large
hot ball are plates that are cool.
These plates, as they rub against one another and as they dive beneath each other, build
up stress during this motion and this stress is eventually relieved through the form of
an earthquake.
If we look at the plates as they exists today on the surface of the planet we see that in
the Sea of Japan there is an intersection of three of these plates and it just so happens
that one plate, the Asian plate, is diving under the North Pacific Plate, precisely where
Okushiri Island exists.
So we can visualize then this process of a plate diving underneath another plate, building
up stress, and as it relieves that stress through a rebounding process it would lift
up the water overlying and produce a tsunami as this animation depicts.
That's the genesis of a tsunami, born of fire.
The map you are looking at shows the areas where the largest earthquake occurred, as
indicated by the red circle and a series of aftershock earthquakes that are indicated
by the small white circles. The combination of this area, which is highlighted by light
blue, is an indication of the area that was actually uplifted during this particular
tsunami-causing earthquake.
So that we have an idea of the spatial dimensions of the formation of this tsunami.
As you can see from this animation, once the tsunami is formed in the Sea of Japan it propagates
very quickly to the island of Okushiri. This wave will continue to wrap around the north
and south parts of the island at the same time it is hitting the other island of Hokkaido
and notice as the two waves wrap around the back side of the island they combine to reinforce
each other to cause wave heights to be unusually large at an unexpected location, at the back
side of the island.
This is not uncommon, because tsunami waves wrap around objects and intersect the island
coastline in a wide variety of ways, but the most important aspect of this is the damage
it causes once it gets near the coastline.
This animation of run-up depicts the overtopping of the southern tip of Aonae and then, notice
how the waves in this animation depict the flooding that takes place along the coast.
So now if we look at the entire process from earthquake generation, shaking this Island
for about 30 seconds, followed by an attack of 3-4 tsunamis lasting for about an hour
that gave rise to fires which burned all night, then we see that the origins of the earthquake
is basically within the bowels of the earth and causes massive destruction and kills people.
Now that you understand how tsunamis are formed and the potential destruction that they can
bring, I would like to share with you a few safety tips of how you can protect yourself
in the event of this natural disaster.
Safety tip #1 is the earthquake itself. If you feel a shaking of the earth while you
are on the coastline, this is nature's warning that a tsunami could have been generated.
So you are advised to seek higher ground as quickly as possible.
Safety tip #2 is unusual water level changes. Oftentimes tsunamis will, as they are approaching
the coastline, the first indication of a tsunami's arrival will be the withdrawal of
water, that is the draining away of the ocean away from the coastline. If you see large
areas of the coastline exposed by this draining of the water, that is a natural warning that
a tsunami is arriving.
So, as quickly as it drained away, it will comeback with an enormous force and a very fast
speed which you cannot outrun. So you are advised if you observe this change in sea
level to seek higher ground as quickly as possible.
Safety tip #3 is the sound of the tsunami. Accounts of massive tsunamis which have created
death and destruction here in the last few decades are always accompanied by a load roar.
[roar of tsunami waves]
So if the tsunami occurs in the evening, it's dark, you cannot see the ocean, you cannot
see the draining of the ocean, and if you hear a load roar from the ocean that too is
nature's indication that a tsunami is approaching.
So the three tips are: you feel an earthquake, if you see unusual wave, sea level changes
on the coastline or hear a load roar from the ocean that's a natural signal a tsunami
is approaching.
If you heed these signs you can save your life by quickly running to higher ground.
[sound of waves crashing]