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1. Tsunami the killerwaves
1. A tsunami(fromJapanese:津波, "harbourwave";[1]Englishpronunciation:
/tsuːˈnɑːmi/[2])or tidalwave,alsoknownas a seismicseawave,
2. seismic seawave,is a seriesof wavesin a waterbodycausedbythedisplacementof a large
volumeof water,generallyinan oceanor a largelake.
3. Earthquakes,volcaniceruptionsandotherunderwaterexplosions(includingdetonations
of underwaternucleardevices),landslides,glacier calvings,meteoriteimpactsandother
disturbancesaboveor belowwaterallhavethepotentialto generatea tsunami.
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2. Tsunami waves
Tsunami waves do not resemble normal undersea currents or sea waves, because their wavelength is far longer.[5] Rather
than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this
reason they are often referred to as tidal waves, although this usage is not favoured by the scientific community
because tsunamis are not tidal in nature. Tsunamis generally consist of a series of waves with periods ranging from
minutes to hours, arriving in a so-called "internal wave train".[6] Wave heights of tens of metres can be generated by
large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous
and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in
human history with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean
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3. Historyof tsunamiwaves
• While Japan may have the longest recorded history of tsunamis, the
sheer destruction caused by the 2004 Indian Ocean earthquake and
tsunami event mark it as the most devastating of its kind in modern
times, killing around 230,000 people.[16] The Sumatran region is not
unused to tsunamis either, with earthquakes of varying magnitudes
regularly occurring off the coast of the island.[17]
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4. Historyof tsunamiwaves
• Tsunamis are an often underestimated hazard in the
Mediterranean Sea and parts of Europe. Of historical and current
(with regard to risk assumptions) importance are the 1755 Lisbon
earthquake and tsunami (which was caused by the Azores –
Gibraltar Transform Fault), the 1783 Calabrian earthquakes, each
causing several tens of thousands of deaths and the 1908 Messina
earthquake and tsunami. The tsunami claimed more than 123,000
lives in Sicily and Calabria and is among the most deadly natural
disasters in modern Europe. The Storegga Slide in the Norwegian
sea and some examples of tsunamis affecting the British Isles refer
to landslide and meteotsunamis predominantly and less to
earthquake-induced waves.
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5. Generation mechanisms
The principal generation mechanism (or cause) of a tsunami is the
displacement of a substantial volume of water or perturbation of the
sea.[21] This displacement of water is usually attributed to either
earthquakes, landslides, volcanic eruptions, glacier calvings or more
rarely by meteorites and nuclear tests.[22][23] The waves formed in this
way are then sustained by gravity. Tides do not play any part in the
generation of tsunamis.
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6. Seismicity
• Tsunami can be generated when the sea floor abruptly deforms and vertically displaces the
overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with
the Earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the
deformed area is displaced from its equilibrium position.[24] More specifically, a tsunami can be
generated when thrust faults associated with convergent or destructive plate boundaries move
abruptly, resulting in water displacement, owing to the vertical component of movement involved.
Movement on normal (extensional) faults can also cause displacement of the seabed, but only the
largest of such events (typically related to flexure in the outer trench swell) cause enough
displacement to give rise to a significant tsunami, such as the 1977 Sumba and 1933 Sanriku
events.[25][
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7. Man-made or triggeredtsunamis
• T h e r e h a s b e e n c o n s i d e r a b l e s p e c u l a t i o n o n t h e p o s s i b i l i t y o f u s i n g n u c l e a r
w e a p o n s t o c a u s e t s u n a m i s n e a r t o a n e n e m y c o a s t l i n e . E v e n d u r i n g W o r l d
W a r I I c o n s i d e r a t i o n o f t h e i d e a u s i n g c o n v e n t i o n a l e x p l o s i v e s w a s e x p l o r e d .
N u c l e a r t e s t i n g i n t h e P a c i f i c P r o v i n g G r o u n d b y t h e U n i t e d S t a t e s s e e m e d t o
g e n e r a t e p o o r r e s u l t s . O p e r a t i o n C r o s s r o a d s f i r e d t w o 2 0 k i l o t o n n e s o f T N T
( 8 4 T J ) b o m b s , o n e i n t h e a i r a n d o n e u n d e r w a t e r , a b o v e a n d b e l o w t h e
s h a l l o w ( 5 0 m ( 1 6 0 f t ) ) w a t e r s o f t h e B i k i n i A t o l l l a g o o n . F i r e d a b o u t 6 k m
( 3 . 7 m i ) f r o m t h e n e a r e s t i s l a n d , t h e w a v e s t h e r e w e r e n o h i g h e r t h a n 3 – 4 m
( 9 . 8 – 1 3 . 1 f t ) u p o n r e a c h i n g t h e s h o r e l i n e . O t h e r u n d e r w a t e r t e s t s ,
m a i n l y H a r d t a c k I / W a h o o ( d e e p w a t e r ) a n d H a r d t a c k I / U m b r e l l a ( s h a l l o w
w a t e r ) c o n f i r m e d t h e r e s u l t s . A n a l y s i s o f t h e e f f e c t s o f s h a l l o w a n d d e e p
u n d e r w a t e r e x p l o s i o n s i n d i c a t e t h a t t h e e n e r g y o f t h e e x p l o s i o n s d o e s n ' t
e a s i l y g e n e r a t e t h e k i n d o f d e e p , a l l - o c e a n w a v e f o r m s w h i c h a r e t s u n a m i s ;
m o s t o f t h e e n e r g y c r e a t e s s t e a m , c a u s e s v e r t i c a l f o u n t a i n s a b o v e t h e w a t e r ,
a n d c r e a t e s c o m p r e s s i o n a l w a v e f o r m s . [ 3 4 ] T s u n a m i s a r e h a l l m a r k e d b y
p e r m a n e n t l a r g e v e r t i c a l d i s p l a c e m e n t s o f v e r y l a r g e v o l u m e s o f w a t e r w h i c h
d o n o t o c c u r i n e x p l o s i o n s .
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8. Warnings and predictions
• Drawbacks can serve as a brief warning. People who observe drawback (many
survivors report an accompanying sucking sound), can survive only if they
immediately run for high ground or seek the upper floors of nearby
buildings. In 2004, ten-year-old Tilly Smith of Surrey, England, was
on Maikhao beach in Phuket, Thailand with her parents and sister, and
having learned about tsunamis recently in school, told her family that a
tsunami might be imminent. Her parents warned others minutes before the
wave arrived, saving dozens of lives. She credited her geography teacher,
Andrew Kearney.
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