TSUNAMI - HARBOUR WAVES
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Transcript of TSUNAMI - HARBOUR WAVES
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SUBMITTED TO:
AR. KAJAL HANDA ARSHI
SUBMITTED BY:
BHANU KHANNA (21008)
PANKHURI MITTAL (21019)
RAHUL PURI (21021)
B.ARCH 10TH SEM
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What is tsunami? A tsunami is a large wave, or series of waves usually
Caused by:
An earthquake
Volcanic eruptions
Underwater explosions or landslides
Meteorite impact
Large earthquakes that cause uplift or
subsidence of sea floor
Underwater landslides
Volcano flank collapse
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Physical characteristics of tsunami:
Wavelength
Normal ocean waves have wavelengths =100 m
Tsunami waves have wavelengths= up to 500
kms.
Wave velocity is the speed of the wave. Velocities of normal ocean waves are about 90 km/hr while tsunami
have velocities up to 950 km/hr
Wave height -distance between the trough and the crest of the wave
Wave amplitude - refers to the height of the wave above the still water line.
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How do tsunamis differ from normal water waves?
Wind-generated waves usually have a period of 5 to 20 sec. And a wavelength of 100 to 200 meters.
Tsunami are characterized as shallow-water waves.
A tsunami can have a period in the range of 10 min. To 2hrs and wavelengths > 500 km.
Wave Refraction is
caused by segments
of wave moving at
different speeds
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Earthquake causes tsunami: The most common causes of tsunamis are underwater
earthquakes.
Tectonic plates are constantly in motion, moving
along each other at a speed
of 1 to 2 inches/year.
The movement occurs along fault lines.
These motions are capable of producing earthquakes and
volcanism, which, when they
occur at the bottom of the
ocean, are two possible
sources of tsunamis
Major tectonic plates on the
earths surface
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A geological theory proposes that earth's lithosphere is broken up into seven major and many minor plates, called tectonic plates.
Tectonic plates or lithosphere plates are large, irregularly shaped
slabs of solid rock, consisting of oceanic and continental
lithosphere.
Earthquake causes tsunami:
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Earthquake causes
tsunami:
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Earthquake causes tsunami:
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Volcanic eruptions causes tsunami: A submarine or offshore
volcanic
eruption can
produce high
magnitude lifts
on seafloors,
which pushes
large water
columns
upwards to
generate
tsunami.
Submarine volcanoes can be detected by the presence of high rock content and steam above
water surface.
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Landslides causes Tsunami Landslides moving into oceans,
bays, or lakes can also generate
tsunami.
Most such landslides are generated by earthquakes or volcanic
eruptions.
As previously mentioned, a large landslide or debris avalanche fell
into lituya bay, alaska in 1958
causing a wave with a run-up of
about 60 m as measured by a zone
completely stripped of vegetation.
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Where and how frequently are tsunamis generated? The pacific ocean
occupies more
than one third of
the earth's
surface and is
bounded by areas
called the ring of fire, which includes
mountain chains,
underwater
trenches, and
islands.
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in the average, there are two
tsunamis per year in the pacific
ocean somewhere, which cause
damage near the source.
Approximately every 15 years a destructive tsunami occurs
in pacific.
The destructive tsunami on dec 26th, 2004 on the indian
coast interms of its impact
seems to have occurred for
the first time in the history.
Where and how frequently are tsunamis generated?
Indian Ocean Tsunami of Dec.26th, 2004
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Why aren't tsunamis seen at sea or from the air?
It is a well known fact that tsunami waves have very low amplitudes and large wavelengths while offshore due to larger
volume of surrounding water.
A typical offshore tsunami wave can have an amplitude A of 1M and a wavelength L of the order of 799.9 kMS. So the energy
associated with these offshore tsunami waves is also very low due
to such lower frequencies, or smaller amplitudes,
these waves are difficult to experience and its virtually impossible
to see them at sea or from air.
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Coastal areas affected from tsunami
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Chronology of 26.12.04 tsunami happened in the Indian Ocean effected 12 countries
around Bay of Bengal and
beyond
triggered by a quake of magnitude 9.3 with its
epicenter west of Sumatra
The quake lifted the seabed by about 5 meters.
Minutes later the tsunami split sending energy pulses
east towards the Sumatra
coast and west across the
open ocean.
As the leading tsunami raced towards Sumatra ,its speed slowed, its wavelength shortened and its
height rose to around 30metres
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In minutes 230,000 people lost their lives, and over 430,000 homes were
reduced to rubble
Chronology of 26.12.04 tsunami
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Over 100,000 fishing boats were destroyed. The livelihoods of over 5
million people were thrown into jeopardy
Chronology of 26.12.04 tsunami
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More than 2,174 miles
of roads destroyed.
Chronology of 26.12.04 tsunami
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What are the factors of destruction from tsunamis? Tsunami causes destruction primarily due to the ultrahigh impacts on structures and other assets.
The basic factors of destruction include, wave impact, erosion , and inundation.
The drag applied by tsunami waves on structures can move them or overturn them.
The presence of high salt concentration in tsunami waves causes corrosion of metallic bodies, which decreases their life ultimately
leading to failure.
Besides the primary destruction, secondary destruction may include fire hazards, and water pollution. Fire hazards may be caused by
severed electricity transmission lines, while damaged oil tankers may
contribute a serious threat to water quality.
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Why are locally generated tsunamis so dangerous?
Locally generated tsunami may reach a nearby shore in less than
ten minutes due to their high speeds. There is not sufficient time
for the pacific tsunami warning center or for local authorities to
issue a warning. For people living near the coast, the shaking of
the ground is the only warning that a tsunami may be imminent.
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Elements at risk: All structures located within 200 m of the low lying coastal area are most
vulnerable to the direct impact of
The tsunami waves as well as the impact
of debris & boulders brought by it.
Structures constructed of wood, mud, thatch, sheets and structures without
proper anchorage to foundations are
liable to be damaged by tsunami waves &
flooding.
Other elements at risk are infrastructure
facilities like ports &
harbors, telephone and
electricity poles,
cables. Ships & fishing
boats/nets near the
coast also add to the
destruction caused by
tsunami waves.
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Elements at risk:
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Hazard Mitigation Strategies: Site Planning and Land Management The designation and zoning of tsunami hazard Areas for such open-space uses as agriculture , parks and recreation, or natural
hazard areas is recommended as the first land use planning
Strategy.
This strategy is designed to keep development at a minimum in hazard areas.
Native vegetation may provide defense (e.g., mangroves for Indian Ocean coastline.
Cluster houses in a staggered pattern to allow proper ventilation. Zigzag patterns avoid wind tunnel effects.
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Seawalls and Bulkheads These are structures placed parallel or nearly parallel to the shoreline to separate the land area from water area.
The primary purpose of a bulkhead is to retain or prevent sliding of the land.
Seawalls are necessarily
massive and
expensive and
should be
constructed only
where the
adjoining shore is
highly developed
and storm attack
is severe.
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Building orientationlearning from the tsunami. The shortest length of building should face the water. allows
the water to move around the structure as efficiently as
possible. The building can also act as a water diverter.
coast line water flow raised platform
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Structures that allow water to move through them: All new buildings must be elevated on pilings, posts, piers, or
columns.
The Spa at the Lighthouse Hotel. The building sustained minor damage during the tsunami, because it had many openings, water moved through it easily.
Pile foundations use long slender
wood, steel, or reinforced concrete
piles that are driven or jetted into the
ground.
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Structures that allow water to move through them: As most of the structures along the coast area comprises of fisherman community, which are constructed of light weight
materials without any engineering inputs.
Therefore ,there is an urgent need to educate the community about the good construction practices that they should adopt
such as:
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Site selection avoid building or living in buildings within several 100ft of the coastline
as these are more likely to experience damage
from tsunami.
Construct the structure on a higher ground level with respect to mean sea level.
Elevate coastal homes: most tsunami waves are less than 3 meters in height . elevating house
will help reduce damage to property from most
tsunamis. Structural columns resist the impact
while other walls are expendable.
Construction of community halls at higher locations , which can act as shelters at the time of a disaster.
note that adequate measures are also brought into the design to cater earthquake forces .
Construction of water breakers to reduce the velocity of waves. Use of water and corrosion resistant materials for construction.
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Tsunami proof house
Improving in technology has enabled man to build tsunami proof houses
which can reduce damage created to ones property one of the most common houses are built as follows :-
Coastal homes are elevated
battery walls can be put .
There must be deep protection to the foundation of the buildings.
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These are built in hydrodynamics
structure which ensures easy flow
of water and protect homes from
collapsing .
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Detection & Warning
- Monitor Earthquake Zones
- Tsunami Warning Systems
a) Seismographs to detect earthquakes
b) Tidal gauges to determine sea level
changes
c) Byud sensors to detect tsunami in open
ocean
Structural Controls
water gate byuo mones house
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Land use
- Native vegetation may provide defense
(e.g., mangroves for Indian Ocean
coastline); protection of coral reefs
- Development of land must be
monitored
Run-up maps
- Show the height to which water is
likely to rise
Tsunami-ready status
- Establish emergency operation center
- Promote community awareness
program
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Detecting tsunami
- only some machines have been introduced
to detect tsunami which mainly depend on
satellites and sonar to detect tsunami.
- Many measures have been taken to
reduce damage created by tsunami.
Government has been giving education to
the coastal people about the dos and don'ts during tsunami.
- many boards have been put up to warn
the people before entering tsunami prone
area