subject: TSUNAMI : HOW AND WHAT OF IT [print this page] TSUNAMI : HOW AND WHAT OF IT... TSUNAMI : HOW AND WHAT OF IT...
Meaning of Tsunami : Tsunami is a Japanese word. Tsu means a port and nami means a wave. Tsunami waves are huge and often very destructive. They are created by natural forces other than lunar gravitation which causes regular tides.
Tsunami is scientifically defined thus : They are waves created by sudden large scale displacement of water. When there is submarine earthquake or volcanic eruption, huge amount of water gets displaced. This sudden movement of water cause Tsunami. If earthquakes are on the land, away from the seacoast, they do not cause Tsunami.
The intensity of the earthquakes decides its destructive power. Though the earthquake is followed by many aftershocks of varied intensity, generally they do not create Tsunamis. This is because, the aftershocks do not cause large scale upheavals or damage to the submarine starta.
Tsunamis are directly related to the mass or volume of the water displaced. Therefore, not only submarine movement of the interior plates of the earth but an exploding volcano or a huge meteor striking the sea from above can also create Tsunamis. e.g., if a gigantic meteor strikes an ocean, it can create huge upheaval in water and the resultant Tsunamis.
The resultant Tsunami in recent memory : The Tsunamis of 26th Dec, 2004 were terrible. An earthquake of 9.0 Richter scale struck the ocean bed near the west coast of Sumatra island of Indonesia and created monstrous Tsunamis. These killer waves travelled a distance of 200 kms and struck the coast of Sri Lanka and India (Tamil Nadu) with full force. The seabed at Sumatra was raised by about 10m, pushing up hundreds of cubic metres of creating huge Tsunamis. At the epicenter, the Tsunamis were only about 1m high and the speed 700 km/hr. When the waves struck the coast of Tamil Nadu the speed was only about 40 km/hr but the waves rose to a height of about 10m. These Tsunami waves caused terrible loss of life and property in 13 countries of South Asia.
Tsunami's movement : When two or more plates of subterranean rocks shift due to frictional movement, an earthquake takes place, lava erupts through the breach in the upper layers and Tsunamis start rising. The effect of Tsunamis seems to be less around rhe epicenter of the earthquake but it assumes a teriffic form when the waves reach the seacoast. The velocity of the Tsunamis may be 700 to 800 km/hr in the beginning but while travelling towards the shallow coastal waters, its velocity decreases and height increases. These Tsunami waves carry millions of metre or so high in the deep seas, rise to about 30 to 40 metres high sweeping everything away.
Forcasting the Tsunamis : These waves can be accurately forcast with the help of Tsunameters (Deep Ocean Assesment and Reporting of Tsunamis), fixed at some places in the pacific ocean. One part of the Tsunanmeter lies on the ocean on the ocean bed and the other floats on the water above. The lower part is so sensitive to pressure that even for one cm diffrence in the sea level, the change in pressure is recorded. Tsunami may be quiet in the mid-seas but a few cms diffrence in the sea level can cause tremendous pressure due to their wide wave-length and this is definitely recorded at the bottom. This is monitored to the floating part in the image. In turn, it is sent to the weather satellite which sends it to a control room. Thus a warning is sent to the places likely to be attacked by the Tsunamis.
Caution : As a member nation, a country may recieve the warning but that is no protection against the terrible Tsunamis. The coastal regions should be so quickly and carefully evacuted that minimum difficulties are caused to the people. These evacuations should be handeled very tactfully. The relief and rescue measures will make little diffrence if not taken quickly, using modern methods. Warning alone is not enough...
