Tsunami

SHOBHIT SRIVASTAVA(026),M.Sc(EM),1ST SEM. 1

�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.2

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 transform3

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”

4

5

�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.

6

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 .

7

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.

8

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.

9

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.

10

VOLCANO CAUSING TSUNAMI

11

�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.12

13

�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.

14

15

� 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.

16

17

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.

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.

18

19

HOW IT ALL OCCURS?20

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 fire21

�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

22

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!!

23

�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!!!

24

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.

25

�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.

26

ORIGINATION OF THE DISASTER27

LOSS OF LIVES & PROPERTY28

�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.

29

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,TILL DECEMBER LIKE THIS,TILL DECEMBER LIKE THIS,TILL DECEMBER LIKE THIS,TILL

THEN…………………….THEN…………………….THEN…………………….THEN…………………….

THANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATIONTHANKS FOR YOUR COOPERATION30