|
|
|
|
|
1.
|
What is a tsunami?
|
|
A tsunami is a series of enormous waves formed in the sea or near the coast and is generated by violent undersea disturbances such as earthquake- induced movement of the ocean floor, landslides and underwater volcanic eruptions. Most tsunamis are caused by earthquakes in the sea that induce movements in the sea floor. From the area where the tsunami originates, waves travel outwards in all directions and can travel great distances. In deep water the tsunami wave is not noticeable, but when it approaches the shore it increases in height. All tsunami are potentially dangerous and can be extremely violent and damaging when they hit the shore.
Not all earthquakes, however, will produce tsunamis. Normally, it would require an earthquake with a magnitude exceeding 7.5 on the Richter scale to produce a destructive tsunami.
|
|
|
|
|
|
2.
|
How fast can a tsunami travel and how soon could it impact on coastal areas after it has formed?
|
|
In deep ocean, tsunami waves can travel at speed exceeding 800 kilometers per hour and a wave height of less than a meter. As they reach the shallow waters of the coast, the waves slow down and the water can pile up into a wall of destruction tens of meters or more in height. The effects can be amplified where a bay, harbour or lagoon funnels the wave as it moves inland. Large tsunamis have been known to rise over 30 meters. Even a tsunami 3-6 meters high can be very destructive and cause many deaths and injuries
Tsunamis can reach coastlines more than 1000 km away within in a few hours.
Graphic from 'Tsunami - The Great Waves' produced by NOAA/IOC/ITIC and LDG, 2002
|
|
|
|
|
|
3.
|
What time of the day are occurrences of tsunamis more likely?
|
|
Tsunami can occur at any time, day or night.
|
|
|
|
|
|
4.
|
Where can additional information on tsunamis be found?
|
|
|
|
|
|
|
|
5.
|
How can we differentiate a tsunami wave from normal ocean waves?
|
|
Tsunami waves are distinguish from ocean waves by their great length between wave crests, often exceeding 100 kilometers or more in the deep ocean and by the time between these crests, ranging from 10 minutes to an hour. Often the first wave may not be the largest. The danger from a tsunami can last for several hours after the arrival of the first wave.
|