Welcome to TsunamiTeacher USA's Tsunami Basics. This short video is intended to provide you
with the basic understanding of tsunamis and how to protect yourself.
>>EYE WITNESS ACCOUNT (Translated): On the morning of September 29th, as you have asked,
around six o'clock in the morning they felt an earthquake occur. Knowing from previous
training that I had received as a Mayor, we waited up in the higher area.
In the next several minutes you will learn, What a tsunami is?
How to recognize dangerous tsunami waves are coming
And what to do if you are in a tsunami hazard or evacuation zone.
Tsunamis are a series of traveling waves often generated by earthquakes.
In the deep ocean, the waves can be up to hundreds of miles long yet only a few inches
or a foot in height. So, if you are on a boat in the deep ocean, you might not notice a
tsunami wave passing beneath you.
As they approach the shallow coast, the wave heights will increase, and in extreme cases
can be up to one hundred feet high when they crash on shore.
Tsunami waves travel very fast in the deep ocean somewhere between four hundred and five
hundred miles per hour, which is the speed of a commercial jet airplane. In this animation
of the September 2009 Samoa earthquake and tsunami, waves took only ten to fifteen minutes
to reach the coasts of American Samoa, Samoa and Tonga and later reached California in
about ten hours.
>>EYE WITNESS ACCOUNT (Translated): Immediately we know the earthquake is so strong that a
tsunami may follow, and it is going to occur just like the blinking of an eye, so please
head for higher ground.
A wave's energy can focus flooding inland, along a road, or up a river. Large debris,
such as cars and trees, act as battering rams causing destruction as the wave moves inland
or recedes. The series of waves can continue to arrive every five to sixty minutes for
several hours. The next wave can arrive before the previous one recedes resulting in greater
water heights and further flooding inland. The first wave also may not be the largest.
These images give you an idea of what tsunami waves may look like to a person on the shoreline.
The waves arrive as walls of water, not as typical breaking or curling wind or surf waves.
At the coast, a tsunami wave will slow down but the waves are still dangerous. This footage
of the 2009 Samoa tsunami shows the ease with which a tsunami wave less than one to two
feet high moved cars.
Remember, even small tsunamis can be extremely dangerous to swimmers and boats in harbors
due to the strong wave currents.
If you see the ocean withdraw out to sea, exposing the ocean bottom or hear the train-like
roar of the tsunami, you might have less than a minute to get to safety.
When an earthquake occurs near the coast, there may be only minutes before tsunami waves
arrive. In this case, the natural warning signs are your alert to act immediately.
Strong coastal earthquakes that shake for more than thirty seconds serve as a natural
warning. Protect yourself first. Drop, cover, and hold on until the shaking stops. When
it is safe, survey the area around you and evacuate by quickly walking inland and to
higher ground.
If wave arrival is imminent, consider vertical evacuation to the highest floors of a multi-story
reinforced concrete building.
>>EYE WITNESS ACCOUNT (Translated): I looked down at the ocean and I saw the ocean was
receding. It was going out. I could see the bottom of the ocean, the floor of the ocean.
I knew then that the tsunami was coming.
These images show the first tsunami wave after it receded at Pago Plaza. The next wave inundating
Pago Plaza arrived within ten minutes of the preceding wave.
>>EYE WITNESS ACCOUNT (Translated): I could hear the wave was coming, and I felt it.
This is a video of a small tsunami generated by an iceberg breaking apart. You will notice
small waves are generated followed by a loud roar produced by the waves. The tsunami then
lifts up fishing boats and relentlessly smashes them onto the shore.
[ROAR OF WAVES, PEOPLE SHOUTING]
All coastlines are vulnerable to tsunamis. Make sure you know your community tsunami
hazard and evacuation zone.
Walk your tsunami evacuation routes so you know where they are located. Remember, in
a local event the natural warning signs are your earliest and possibly only alert.
The US's West Coast Alaska Tsunami Warning Center and Pacific Tsunami Warning Center
are monitoring earthquakes all the time and will issue official warnings but they may
not be in time to warn for a local tsunami. So, do not wait for the official warnings.
Based on the tsunami's natural warning signs, act immediately.
>>EYE WITNESS ACCOUNT (Translated): Immediately we know the earthquake is so strong that a
tsunami may follow, and it's going to occur just like the blinking of an eye, so please
head for higher ground.
[SLOSHING OF WAVES]