Tsunami Report
TSUNAMI REPORT
An Overview of Tsunamis
By
Banyae Ein
Guadie Kassie
Travis Young
Matt Aughey
Brannan Hartill
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Abstract
We picked tsunamis as our group project topic. To present the information in an easy to
follow way we broke it down into 4 categories: The definition, history, causes, and physics of a
tsunami. A Tsunami is a series of water waves caused normally by earthquakes and less
commonly by volcanic eruptions, underwater explosions, landslides or meteors impacting the
earth. Tsunamis have been found throughout history in records, the first dating back to 1628 BC.
Tsunamis are extremely destructive with waves reaching 100 feet high. Tsunamis are very
deadly because of how hard they are to detect. While moving at up to 500 mph in the ocean and
passing right below ships almost undetected, they can reach the shoreline before any ample
warning has been made.
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Definitions of a Tsunami
A tsunami is a huge ocean wave that can travel at speeds up to 500 mph and hundreds of
miles over open sea before it hits land. Sometimes incorrectly called a tidal wave, a tsunami is
usually caused by an earthquake, volcanic eruption or coastal landslide.
The term Tsunami comes from the Japanese meaning “tsu” harbor and “nami” wave. It is,
in fact, a series of waves which travel outward on the ocean surface in all directions in a kind of
ripple effect. Since the waves can start out hundreds of miles long and only a few feet high, they
would not necessarily be noticeable to a passing ship or a plane flying overhead.
A tsunami that is generated from close-by can reach the shore in less than ten minutes.
This does not allow authorities time to issue a warning. The only warning might be movement in
the ground, which could alert people close to the shore that a tsunami is imminent. If a major
earthquake gives cause to suspect a tsunami, one of the following warnings may be issued:
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Tsunami information bulletin — announcing that a threat exists.

Tsunami watch — announcing that the tsunami is likely and residents should be alert.

Tsunami warning — giving expected arrival times of a tsunami.
Areas at greatest risk are usually within one mile (1.6 km) of the shoreline and less than 25
feet (7.6 meters) above sea level. Since the tsunami arrives as a series of waves, the danger exists
even after the first wave hits. Often, subsequent waves may be more dangerous than the first one.
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The force of the tsunami is enormous, with waves carrying huge boulders, trees, buildings and
vehicles in its wake. It can wrap around an island and be just as dangerous on the far side of the
island as on the side facing the source of the tsunami.
What you need to know to prepare for a tsunami:
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Since earthquakes frequently precipitate a tsunami, if an earthquake happens, expect a
tsunami warning in its wake. Leave low-lying areas until the danger passes.

As a tsunami approaches there is often a noticeable drop in sea level; take it as nature's
warning to leave the area. An incoming tsunami often sounds like an oncoming train —
another of nature's warnings.

Though a tsunami may be small and harmless on one point on the shore, a little further
away it could be much larger and carry far greater dangers.

Do not go to the shore to look for a tsunami; if you can see it, you are already too close to
outrun it.

You should never try to surf a tsunami; the wave does not behave like a regular wave,
curling or breaking.

If you are at the beach and feel the earth shake, immediately move to higher ground.
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Drowning is the cause of most tsunami-related deaths. Other dangers to property and
person include flooding, fires from ruptured tanks or gas lines, contaminated drinking
water, and the loss of vital community infrastructure (police, fire, medical).
History of Tsunamis
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Through geological evidence and historic records, there is a wealth of knowledge about
an incredibly vast number of tsunamis.
Geological Evidence
The earliest tsunami likely took place 35 million years ago, when an asteroid struck the
Chesapeake Bay area in what is now the eastern United States. Little is known, or even
speculated, about this tsunami and its possible destructive qualities. One tsunami about which we
do have some speculation happened approximately 8,000 years ago, when volcano near Sicily
erupted causing an avalanche that crashed into the Mediterranean Sea at an incredible speed of
200 miles per hour. This avalanche caused a tsunami that spread across the entire Mediterranean
Sea. Because no historical record of this event exists, there is no way of knowing exactly how
devastating this tsunami was, although scientists believe it was taller than a 10-story building.
Historical Records
It is not possible to tell when the first, historically recorded tsunami took place due to the fact
that the Chinese and Japanese have many records of tsunamis with out any date. However, there
are records of a tsunami, originating from a volcano eruption on Santorini Island, that could date
back to as early as 1628 BC.
One of the earliest, note-worthy tsunamis took place in the summer of 426 BC. The
tsunami hit the Maliakos Bay in eastern Greece and was recorded by the Greek historian,
Thucydides. This particular tsunami is worth mentioning, not for the tsunami itself, but rather the
record. Thucydides recognized a series of earthquakes as the cause for the tsunami and became
the first person in history to note the correlation between earthquakes and tsunamis.
Tallest Tsunami
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The tallest tsunami ever recorded was the 1958 Lituya Bay mega tsunami. An earthquake
with a Richter scale reading of 7.9 struck near Lituya Bay, Alaska and caused a wave that
reached 1,720 feet high, 250 feet higher than the Empire State Building. By comparison, the
average height for a “larger tsunami” is 30-70 feet, and the only other megatsunami in recent
history (the 1963 Vajont Dam tsunami) was 750 feet tall.
Deadliest Tsunami
The deadliest tsunami on record is the 2004 Indian Ocean tsunami. On December 26,
2004, an earthquake with the third largest Richter scale reading ever recorded on a seismograph
(9.3) under the Indian Ocean released energy equivalent to 23,000 atomic bombs. The resulting
waves traveled more than 3,000 miles in some directions and were over 50 feet high. By the end
of the day, more than 150,000 people in 11 countries were dead or missing and millions more
were homeless. All in all, an estimated 230,000+ people were killed by this tsunami. This picture
shows the countries effected (in yellow) as well as the tsunami creating earthquake’s epicenter.
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This next picture shows a fraction of the total damage done to the effected area. Areas along the
costal zone effected look similar if not worse then the damage done in this picture.
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Causes
Earthquakes generally cause tsunamis, also called seismic sea waves or, incorrectly, tidal
waves, less commonly by submarine landslides, infrequently by submarine volcanic eruptions
and very rarely by a large meteorite impact in the ocean. Submarine volcanic eruptions have the
potential to produce truly awesome tsunami waves. The Great Krakatau Volcanic Eruption of
1883 generated giant waves reaching heights of 125 feet above sea-level, killing thousands of
people and wiping out numerous coastal villages.
Not all earthquakes generate tsunamis. To generate tsunamis, earthquakes must occur
underneath or near the ocean and be large and create movements in the sea floor. All oceanic
regions of the world can experience tsunamis, but in the Pacific Ocean there is a much more
frequent occurrence of large, destructive tsunamis because of the many large earthquakes along
the margins of the Pacific Ocean. On the next page is a picture of how a tsunami might be made
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when two tectonic plates move across each other on the ocean floor. Notice the release of built
up energy and then the following waves after.
Subduction Zones are Potential Tsunami Locations
Earthquakes generated in a subduction zone, an area where plate tectonic forces are
forcing an oceanic plate down into the mantle, cause most tsunamis. The friction between the
subducting plate and the overriding plate is enormous. This friction prevents a slow and steady
rate of subduction and instead the two plates become "stuck". As the stuck plate continues to
descend into the mantle the motion causes a slow distortion of the overriding plate. The result is
an accumulation of energy very similar to the energy stored in a compressed spring.
Ring of Fire
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The waters of the four oceans cover about two-thirds of the earth. The Pacific Ocean is
the world's largest, covering more than one third of the total surface area of our planet. The
Pacific Ocean is surrounded by a series of mountain chains, deep ocean trenches and island arcs,
sometimes called a "ring of fire." The great size of the Pacific Ocean and the large earthquakes
associated with the "ring of fire" combine to produce deadly tsunamis.
People living near areas where large earthquakes occur may find that the tsunami waves
will reach their shores within minutes of the earthquake. For these reasons, the tsunami threat to
many areas (Alaska, the Philippines, Japan or the U.S. West Coast) can be immediate (for
tsunamis from nearby earthquakes taking only a few minutes to reach coastal areas) or less
urgent (for tsunamis from distant earthquakes taking from 3 to 22 hours to reach coastal areas).
Earth and Earthquakes
The continents and sea floor that cover the earth's surface are part of a world-wide system
of plates that are in motion. These motions are very slow, only an inch or two per year.
Earthquakes occur where the edges of plates run into one another. Such edges are called fault
lines or faults. Sometimes the forces along faults can build-up over long periods of time so that
when the rocks finally break an earthquake occurs. Examples of features produced by forces
released along plate edge faults are the Andes Mountains in South America (on land) and the
Aleutian Trench near Alaska (under water). When powerful, rapid faulting occurs underneath or
near the ocean, a large earthquake is produced and, possibly, a tsunami. The deep ocean trenches
off the coasts of Alaska, the Kuril Islands, Russia,, and South America are well known for their
violent underwater earthquakes and as the source area for destructive Pacific-wide tsunamis.
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The tsunami generating process is more complicated than a sudden push against the
column of ocean water. The earthquake's magnitude and depth, water depth in the region of
tsunami generation, the amount of vertical motion of the sea floor, the velocity of such motion,
whether there is coincident slumping of sediments and the efficiency with which energy is
transferred from the earth's crust to ocean water are all part of the generation mechanism.
It should come as no surprise than that the Pacific Ocean is a source of the vast majority
of tsunamis. This area is one of the most geologically active in the world, as the Pacific Ocean
basin is surrounded by deep ocean trenches, explosive volcanic islands, and mountain ranges as
well as the frequent earthquakes and volcanic eruptions that occur nearby.
Physics of a Tsunami
Tsunamis occur when a huge displacement of water is caused by a number of things.
Tsunamis are most prevalent in the ocean but can happen in large lakes as well. When the sudden
displacement of a lot of water from its equilibrium point happens the water tries to return to
equilibrium causing movement.
The wavelength of a Tsunami can be up to 120 mi (200 km) long and travel up to speeds
of 500 mph (800 kph). A Tsunami's wavelength is enormous but the amplitude is very small,
only about 3.3 feet (1 meter) and the wave vibrations can take between 20 to 30 Min's from wave
to wave. In deep waters a Tsunami can pass underneath a boat undetected. When the Tsunami
wave reaches the shallow shoreline its velocity slows down drastically (80 kph or 50 mph) and
its amplitude can increase to over 100 ft. Tsunamis are shallow-water waves because of their
extremely long wavelengths. A wave loses energy proportionally to its wavelength. Since the
wavelength is so big it losses very little energy as it travels. A tsunami can travel from one side
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of the Pacific Ocean to the other in less than a day. Below is a picture showing the effects of a
Tsunami as it comes closer to shore. Notice how the amplitude increases when there is a smaller
supply of water.
An equation to find the speed of a Tsunami is, Speed of a tsunami = Square root
(acceleration of gravity x ocean depth)
Tsunamis have amazing erosion abilities, they wipe out beaches and destroy other
shoreline vegetation like trees and dirt and coastal homes and buildings. Main risks of a Tsunami
are drowning. Floods can reach heights of 1000 feet. When tsunamis reach the shoreline they
lose some energy due to Newton’s Law of third law, turbulence, and friction but even with these
losses the energy is still tremendous as stated earlier. The force of a tsunami can also be found
using the equation, P = pgh when P = overlying pressure in Newton’s per meter square, p is
equal to the sea waters density, g is equal to the acceleration of gravity and h = the water column
height in meters. A quick example would be a water column that is about 6,000 meters deep
would have a tsunami with the force of about 6460 tons-force per meter.
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Conclusion
Tsunamis are some of nature’s most destructive forces. With almost unrivaled power
Tsunamis are the ocean’s most powerful waves. A single Tsunami can destroy a costal town with
just one wave. With such examples as the 2004 Indian Ocean Tsunami tsunamis are some of
nature’s most deadly killers. While our group was researching this topic our group came to
understand the absolute power and destructive force of tsunamis and an overall respect for
physics and how it can help people. With better technology and understanding, one day we can
have an advanced tsunami warning system that will help warn costal zones of incoming
tsunamis. We hope this paper has helped you understand the history, causes, and physics of
tsunamis.
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Reference List
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World Wide Web: http://www.sitnews.us/Kiffer/LituyaBay/070808_lituya_bay.html
LiveScience Staff (2010). Tsunamis in history. Retrieved Oct 31, 2010 from the World
Wide Web: http://www.livescience.com/environment/tsunami_history.html
Mofjeld, Hal (2005) Retrieved Oct 31 2010, from the World Wide Web:
http://nctr.pmel.noaa.gov/faq_display.php?kw=25%20February%202005%20Interview%
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Mofjeld, Hal (1998) Retrieved Oct 31 2010, from the World Wide Web:
http://nctr.pmel.noaa.gov/faq_display.php?kw=1998%20Interview%20with%20Dr.%20H
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National Geographic News (2005). The deadliest tsunami in history? Retrieved Oct 31,
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http://news.nationalgeographic.com/news/2004/12/1227_041226_tsunami.html
Woodworth, Harry G. (2008). Tsunami: tidal waves and other extreme waves. Retrieved
Oct 31, 2010, from the World Wide Web:
http://www.erh.noaa.gov/er/phi/reports/tsunami.htm