Sunday, December 26, 2004

physics of tsunami

what is a tsunami?

I was wondering what is a tsunami. This is what is found out.To put in simple terms. Imagine the ripples that you used to create with the bed sheet or saree. say u are the person who is starting the ripple from one end and ur friend is holding the other end of the cloth .In a tsunami you are the seismic movement and your friend is the sea shore. Imagine the seismic movement creating a big ripple from the middle of the ocean.A ripple what is 200/300 mile long.

The seismic movement say for example caused a sudden elevation on the sea bed.It changes the equilibrium and displaces lot of water vertically. Imagine a motor cyclist coming across a speed breaker.Well in the case of a motor cyclist he goes up and the energy that displaced him looses momentum due to gravitational pull and he is back on the surface. In the case of the tsunami the waves dont looses there energy. How??


The high waves that hit the coast were not that high at the point of origin.If they would have been that high. They would have lost the energy and would have died on the way.The energy was more under the surface than over the surface. The rate at which a wave loses its energy is inversely related to its wave length(distance between two success ional waves).Longer the wave length smaller is the energy loss.

The tsunami waves looses its speed as it approaches the shore. Say it was started at a 1000m depth, the whole water mass of 1000m depth is set into motion. But by the time it reaches the shore the depth gradually reduces, slowing down the waves. But the energy that it was coming with is transformed into high waves.

AS far the tsunami that hit south india. It originated where two plates in the Earth's crust - the India and Burma plates - collide. A 620-mile segment of the boundary snapped. Suddenly the Burma plate's margin stood at least 15 meters higher than the India Plate. With a preliminary magnitude of 8.9, the quake was the strongest anywhere in the globe in the last 40 years and perhaps the strongest ever recorded in this region.

Very nice article sen !!
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