Tsunamis are large ocean waves generated by earthquakes, landslides, or volcanic eruptions. When the 2004 Indian Ocean earthquake occurred, it generated a devastating tsunami that killed over 160,000 people across several Asian and African countries. The disaster could have been mitigated if an early warning system had been in place for the Indian Ocean similar to the one that exists in the Pacific. International efforts are now underway to develop an early warning system for the Indian Ocean and other regions to help prevent future loss of life from tsunamis.
2. The phenomenon we call “TSUNAMI”(soo-NA
hmee) is a series of travelling ocean waves of
extremely long length generated primarily by
earthquakes occurring below or near the ocean floor.
Tsunami waves are distinguished from ordinary
ocean waves by their great length.
In the deep ocean ,the tsunami waves propagate at
a speed exceeding 800 kmph.
Tsunami is a kind of Coastal Hazard.
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3. Plate tectonic theory is based on an earth model
characterized by a small number of lithospheric belts,70 to
250km,that float on a thick viscous under layer called the
asthenosphere.These plates cover the entire surface of the
earth & contain both continents & seafloor.
The region where the two plates come in contact is called
a plate boundary.
When the two plates move away from each other ,it is
called as Spreading.
Where the two plates move towards each other &one
slides beneath the other is called Subduction
Where the two pates slide horizontally past each other,
it is known as transform 3
4. Subduction zones are characterized by Deep ocean
Trenches, and the volcanic islands or mountain chains
associated with many subduction zones around the Pacific
Rim are known as “The Ring Of Fire”
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6. Not all earthquakes generate tsunamis. To generate a
tsunami, the fault must be underneath or near the ocean.
Shallow focus earthquakes (depth <70km) along
subduction zone are responsible for most destructive tsunamis.
Tsunami also called seismic sea wave are caused generally
by earthquakes, less commonly by submarine
landslides,infrequetly by submarine volcanic eruptions &
rarely by large meteorite impacts in the ocean.
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7. In the deep ocean,destructive
tsunamis can be small-often only
a few tens of cms or less in height
& cannot be seen nor felt on ships
at sea. But as the tsunami reaches
shallower coastal waters, wave
height can increase
rapidly.Sometime,coastal waters
are drawn into the ocean just
before the tsunami strikes. When
this occurs, more shoreline may be
exposed than even at the lowest
tide. This major withdrawal of the
sea should be taken as a warning
of the tsunami waves .
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8. Where the ocean is over 6000 m deep, unnoticed
tsunami waves can travel at the speed of a
commercial jet plane, over 800kmph. Scientists can
predict when a tsunami will arrive at various places
by knowing the source characteristics of the
earthquake that generated the tsunami and the
characteristics of the seafloor along the paths to
those places. Tsunamis travel much slower in shallower
coastal waters where their wave-heights begin to
increase dramatically.
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9. Offshore & coastal features can determine the size &
impact of tsunami waves. When the tsunami reaches the
coast & moves inland, the water level can rise many
metres.In the extreme cases, water level has risen to more
than 15m(50ft) for tsunamis of distant origin and over
30m(100ft) for tsunami waves generated near the
earthquake’s epicenter.
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10. Although relatively infrequent, violent volcanic eruptions
represent also impulsive disturbances, which can displace a
great volume of water & generate extremely destructive
tsunami waves in the immediate source area. According to this
mechanism, waves may be generated by the sudden
displacement of water caused by a volcanic explosion.
One of the largest & most destructive tsunamis ever recoded
was generated in August 26,1883 after the explosion &
collapse of the volcano of Krakatau(Indonesia).This explosion
generated waves that reached 135ft,destroyed towns
&villages, and killing 36,417 people.
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12. Tsunami waves can be generated from displacements of
water resulting from rock-falls, icefalls & sudden submarine
landslides or slumps.
Major earthquakes are suspected to cause many
underwater landslides, which may contribute significantly to
tsunami generation
In the 1980’seath moving & construction
work of an airport runway along the
coast of Southern France,trrigered an
underwater landslide, which generated
tsunami waves in the harbor of Thebes.
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14. The Richard H. Hagemayer Pacific Tsunami Warning
Centre(PTWC) serves as the international warning centre for
tsunamis that pose a Pacific-wide threat.
PTWC became a formal arrangement in 1965 as the
operational centre for Tsunami Warning System in the
Pacific(TWSP).
The initial objective of PTWC is to detect, locate
&determine the seismic parameters of potentially
tsunamigenic earthquake occurring in the Pacific Basin.
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It continuously receives seismographic data from more
than 150 stations around the pacific.
If the earthquake location, depth,& magnitude criteria
needed to generate a tsunami are met, a tsunami warning
is issued to warn of an imminent tsunami hazard.
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The National Oceanic & Atmospheric Administration(NOAA)
of U.S & various international science agencies have
indicated that there were few, if any tsunami early warning
systems monitoring the Indian Ocean on 26thDec.,2004.
However, nations bounded also by the Pacific Ocean,
including Australia &Indonesia, had tsunami early warning
system monitoring the Pacific shores where they perceived a
threat
While earthquakes couldn’t be predicted in advance, once
the earthquake was detected it was possible to give about
3hrs advance notice of a potential tsunami, such a warning
system is in place across the Pacific but not in Indian Ocean.
18. On the contrary, scientists knew in advance that Southern
Asia was going to be hit by the tsunami
But attempts to raise the alarm were hampered by the
absence of "EARLY WARNING SYSTEMS” in the region.
Within 15min. of 26th Dec. earthquake, the PTWC in Hawaii
had sent an alert to 26 countries, including Australia &
Indonesia, but because of the lack of infrastructure to
receive warnings rapidly,
it had to face the havoc of
tsunami.
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21. Mainly there are three “FACTORS OF DESTRUCTION OR
EFFECTS” of tsunami-
Inundation
Wave impact on structures
Erosion.
Strong tsunami-induced currents lead to erosion of
foundations and the collapse of bridges & seawalls.
Floatation & drag forces move houses &overturned
railroad cars.
Floating debris, including boats & cars become dangerous
projectiles that may crash into buildings, break power line
&may start fire
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22. Fires mainly come from damaged ships in ports or from
ruptured coastal oil storage tanks & refineries, can cause
damage greater than that inflicted directly by the tsunami
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23. If you feel an earthquake & you are near the sea or
ocean you may need to do the following-
DURING TSUNAMI
Listen to a radio or television to get the latest emergency
information, and be ready to evacuate if asked to do so If
you hear an official tsunami warning, evacuate at once.
Climb to higher ground. A tsunami warning is issued when
authorities are certain that a tsunami threat exist.
Stay away from the beach, NEVER go down to the
beach to watch a tsunami come in. If you can see the wave
you are too close to escape it!!
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24. Return home only after authorities advise it ids safe to
do so. A tsunami is a series of waves .Do not assume that
one wave means the danger is over. The next wave may
be larger than the first one. Stay out of the area!!
AFTER TSUNAMI
Stay tuned to a battery-operated radio for the latest
emergency information.
Help injured or trapped persons.
Give first-aid if you can.
Do not move seriously injured persons unless they are in
immediate danger of further injury.
Call for help!!!
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25. On Dec.26th 2004,a magnitude 9.0 undersea earthquake
off the west coast of Northern
Sumatra(Indonesia),unleashed a
tsunami that affected more than
12 countries throughout south &
southeast Asia & stretched as far
as the northeastern African coast.
Within 6 hrs. the deadly waves
travelled more than 3,000 miles &
carved a trail of death &
destruction as they arrived on land.
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26. Current official estimates indicate that more than
160,000 people are dead,& millions of others are
affected, including the injured, missing & displaced.
The World Health Organization (WHO) indicates that an
estimated 3-5 million people lack the basic necessities for
survival; between 1-2 million people may be displaced.
A massive, global relief & recovery operation is
underway. After about 4 years of misery, their lives have
started to come on track.
According to the United Nations, the relief operation is
the largest ever undertaken.Indonesia,Sri Lanka,India
&Thailand have suffered some of the worst devastation.
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29. Development of such a system needs financial support
from every country of the world.
Developed countries have to bear most of the expenses,
which includes, cost of procuring, operating &maintaining the
system.
United Nations Environment Program(UNEP) announced an
international effort to develop an early warning system for
the nations bounding the Indian Ocean.
Expansion of the existing U.S tsunami early warning
program in the Pacific is also on the cards, so as to include
sites of the Indian & Atlantic Ocean in the system.
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30. HOPE WE WON’T GET ANOTHER 26HOPE WE WON’T GET ANOTHER 26HOPE WE WON’T GET ANOTHER 26HOPE WE WON’T GET ANOTHER 26thththth
DECEMBER LIKE THIS,TILLDECEMBER LIKE THIS,TILLDECEMBER LIKE THIS,TILLDECEMBER LIKE THIS,TILL
THEN…………………….THEN…………………….THEN…………………….THEN…………………….
THANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATION
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