What is a tsunami? • A tsunami is a series of waves created when water is moved very quickly. Underwater earthquakes are the most common causes of tsunamis, but underwater volcanic activity can also trigger a displacement in the water, and create a mega-wave.
• First tsunami was recorded in 1480 B.C. in easternMediterranean, when the Minoan civilization was wapedout.• A large tsunami accompanied by the earthquake ofLisbon in 1755.• North and South American records have dated suchevents back to 1788 for Alaska and 1562 for Chile. Recordsof Hawaiian tsunami go back to 1821.• Tsunami hits the Mona Passage off Puerto Rico in 1918,grand banks of Canada in 1929.
Hawaiian tsunami on 1 April 1946 destroyed the city of Hilo, killing 159 people. Other recent tsunami that have hit Hawaii are those of 1952,1957,1960,1964 and 1975 . Total 65 destructive tsunamis struck Japan between 684 A.D to 1960. On 16 August 1976, a large earthquake in the Moro Gulf in the Philippines generated a destructive local tsunami which killed over 8,000 persons. Last one was Christmas tsunami in 2004.
Tsunami "Wave Train"Many people have the mistaken belief thattsunamis are single waves. They are not.Instead tsunamis are "wave trains" consistingof multiple waves. The chart below is a tidalgauge record from Onagawa, Japan beginningat the time of the 1960 Chile earthquake. Timeis plotted along the horizontal axis and waterlevel is plotted on the vertical axis. Note thenormal rise and fall of the ocean surface,caused by tides, during the early part of thisrecord. Then recorded are a few waves a littlelarger than normal followed by several muchlarger waves. In many tsunami events theshoreline is pounded by repeated large waves.
• Volcanic eruptions and icefalls create disturbance in water and generate tsunami.• Heavy rainfall cause overflow of water and generate tsunamis.
.Tsunami can be generated when the see 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 see, the water above the deformed area is displayed from its equilibrium position..Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium
• Ocean waves are normally divided into 3 groups, characterized by depth:• • Deep water• • Intermediate water• • Shallow water• Even though a tsunami is generated in deep water (around 4000 m below mean sea level), tsunami waves are considered shallow-water waves. As the tsunami wave approaches the shallow waters of shore, its time period remains the same, but its wavelength decreases rapidly, thus causing the water to pile up to form tremendous crests, in an effect known as "shoaling".
Subduction Zones are Potential Tsunami LocationsMost tsunamis are caused by earthquakes generated in a seduction zone, an area wherean oceanic plate is being forced down intothe mantle by plate tectonic forces. Thefriction between the sub ducting plate and the overriding plate is enormous.This friction prevents a slow and steadyrate of seduction and instead the two plates become "stuck".
Accumulated Seismic EnergyAs the stuck plate continues to descend into the mantlethe motion causes a slow distortion of the overriding plage.The result is an accumulation of energy very similar to theenergy stored in a compressed spring. Energy canaccumulate in the overriding plate over a long period oftime - decades or even centuries.
Tsunamis occur most frequently in the PacificOcean, but are a global phenomenon; they are possiblewherever large bodies of water are found, including inland lakes, wherethey can be caused by landslides.Japan is a nation with the most recordedtsunamis in the world. The earliest recorded disaster being thatof the 684 A.D.
.Tsunami is one of the earth’s disaster. It was a Japanese wordmeaning “harbor wave,” used as the scientific term for a classof abnormal sea wave that can cause catastrophicdamage when it hits a coastline..Tsunamis can be generated by an undersea earthquake,an undersea landslide, the eruption of an undersea volcano,or by the force of an asteroid crashing into the ocean.
The earthquake that caused the Sumatran tsunami is the second largest to ever be recorded on a seismograph. The magnitude of the earthquake was 9.3 on the Richter scale. This earthquake had the longest duration, that is lasted for the longest amount of time, ever observed, lasting approximately 10 minutes. It caused the entire planet to vibrate by as much as 1 cm (0.5 inches), and triggered other earthquakes as far away as Alaska.
There were no Tsunami Warning Systems in the Indian Ocean on the 26th December 2004. Had there had been, many lives could have been saved. A 10 year old tourist named Tilly Smith, who had studied tsunamis at school, noticed the receding tide and frothing bubbles, and told her parents there was going to be a tsunami. Her parents told the rest of the beach and everyone was evacuated safely.
GENERATION OF TSUNAMIS A Tsunami is generated when a large amount of water is displaced which is done-: Mainly By The Earthquakes. By The Landslides. By Volcanic Eruptions. By Impact Events like Meteorite impacts
Earthquakes – The Major Cause The Sea floor abruptly deforms and displaces the sea water lying above. Large vertical movements of earths crust can occur at plate boundaries which are called “faults”.
Tsunamis may reach a maximum vertical height onshore above sea level, often called a run up height, of 10, 20, and even 30 meters. For a typical ocean Depth of 4000m, a tsunami moves with a speed about 700km/hr. The fast-moving water associated with the inundating tsunami can crush homes and other coastal structures.
Signs Of An Approaching Tsunami Often no advance warning of an approaching Tsunami An earthquake felt near a body of water may be considered an indication that a tsunami will shortly follow.
WARNINGS AND PREVENTION Early warnings come from the nearby animals as they sense danger and flee to higher grounds. Tsunami walls for the reduction in the damage. Tsunami warning system alert the people before the wave reaches the shore
Tsunami death toll tops 118,000. Around 10,000 killed in India. In Thailand, more than 4,000 are feared dead and dozens of deaths are reported in Malaysia, Myanmar and Maldives. WHO estimates five million people are without basic needs.
Calong, A land of 13,000 “ vaporized” by Tsunami
The Tsunami That Struck Thailand OnDecember 26, 2004
The Islamic Relief Responded to the emergency in hours. Building enough homes to accommodate five families a week. Highly successful because of the close and constant involvement of the affected communities. Still working for the betterment of the victims.
RELIEF WORKS IN INDIA Donations done under the Prime Minister Relief Fund. Rice, mats, medicines were provided. ITC distributed over 1 lakh shirts to the victims. New houses were provided.
Loss of life and property can be reduced by proper planning. Tsunami warnings can be made to aware peoples. Stay away from all low lying coastal areas. Never go down to the shore to watch tsunami. Stay out of low lying danger areas until an “all-clear” is issued by competent authority.