A tsunami is a series of waves or surges that are caused due to sea floor displacement. Tsunami has an associated force that causes the sea-floor to move abruptly resulting in sudden displacement of ocean water in the form of high vertical waves. The impact of this movement on nearby coasts, property and lives can be devastating.
Normally, the seismic waves cause only one instantaneous vertical wave; but, after the initial disturbance, a series of after waves are created in the water that oscillate between high crest and low trough in order to restore the water level.
The speed of wave in the ocean depends upon the depth of water. It is more in the shallow water than in the ocean deep.
As a result of this, the impact of tsunami is less over the ocean and more near the coast where they cause large-scale devastations. Therefore, a ship at sea is not much affected by tsunami and it is difficult to detect a tsunami in the deeper parts of sea
Thus, these are also called Shallow Water Waves. Tsunamis are frequently observed along the Pacific ring of fire, particularly along the coast of Alaska, Japan, Philippines, and other islands of South- east Asia, Indonesia, Malaysia, Myanmar, Sri Lanka, and India etc.
The mitigation of hazards created by tsunami is difficult, mainly because of the fact that losses are on a much larger scale-combined efforts at the international levels are the possible ways of dealing with these disasters as has been in the case of the tsunami that occurred on 26th December 2004 in which more than 300,000 people lost their lives. India has volunteered to join the International Tsunami Warning System after the December 2004 tsunami disaster.