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Damage Assessment of Tsunami in Coastal Stretch of Chennai Using High Resolution Data
K Karuna Sankar
Student
INSTITUTE OF REMOTE SENSING, ANNA UNIVERSITY,
India
Email: karunasankar_k@yahoo.co.in
ABSTRACT
Tsoo-nah-mee, the Japanese word meaning harbour wave is basically a wave train, generated in the ocean due to sudden disturbance that vertically displaces the water column. The causative factor of such an impulse can be ocean-floor tectonics (earthquakes and volcanic eruptions) or mass movements in the continental slope. All these processes result in elevating (potential energy) the water column up above the mean sea level, which then horizontally propagates (kinetic energy) as tsunami. Thus the tsunami differs from the tidal wave in that the latter has very low-order energy, since it originates due to gravitational forces. The tsunami once generated is split into distant (propagating towards ocean) and local (propagating towards nearby coast) tsunamis, which travel in opposite directions with amplitude about half of the original. Both tsunamis have a wavelength more than 100 km and period of the order of about 1 h. Since the speed of the tsunami varies as the square root of water depth, it travels faster in the open ocean than near the coast.
As the tsunami moves from the deep ocean to the shore, its amplitude increases and wavelength decreases. This results in the steepening of the tsunami run-up, a measure of the height of the water on shore. After hitting the shore, a part of the tsunami energy is reflected back to the open ocean and also results in generation of edge waves that travel back and forth parallel to the shore. The generation of run-up and edge waves is complex depending upon the slope, smoothness, wave type, depth of water and coastal topography.
At around 7.58 am local time on 26 December 2004 an undersea earthquake, with a magnitude of 9 on the Richter scale, occurred some 250 kilometers off the coast of Sumatra, Indonesia. It triggered a devastating tidal wave or “tsunami” measuring around 10 meters high and traveling at 500km/hour. It hit several countries in the Indian Ocean, including: Indonesia, Sri Lanka, India, Thailand, Myanmar, Bangladesh, the Maldives, the Seychelles, Yemen, Somalia, Kenya and Tanzania. The first quake was followed by aftershocks ranging from 6 to 7.3, themselves large enough to destroy thousands of
lives and livelihoods. It is estimated that as many as 150,000 people may have lost their lives.
1. To prepare a map depicting the Pre and Post situations of the Tsunami.
2. To find the area affected by Tsunami by change detection.
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