tsunami destruction get us an early warning system?
By Apsara Kapukotuwa
Experts say that in the midst of all the tragedy,
the window of opportunity now created for the establishing of an
Early Warning System for tsunamis must not be ignored. The Pacific
Ocean already has a well-equipped warning system based in Hawaii
and the need for one in the Indian Ocean is now only too apparent.
Sunday's underwater quake, which the U.S. Geological Survey put
at magnitude 9.0 in the Richter scale, was the biggest since 1964,
when a 9.2-magnitude temblor struck Alaska, also touching off a
tsunami. There were at least a half-dozen powerful aftershocks and
even one of magnitude 7.3. Enzo Boschi, the head of Italy's National
Geophysics Institute, likened the quake's power to detonating a
million atomic bombs the size of those dropped on Japan during World
War II and said the shaking was so powerful it even disturbed the
earthquake occurred at a spot where the Indian Ocean plate is gradually
being forced underneath Sumatra -- which is part of the Eurasian
plate -- at about the speed at which a human fingernail grows, according
to David Booth, a seismologist at the British Geological Survey.
Ninety-five percent of the world's seismic activity happens in the
Pacific, which is why Sunday's devastation around the Indian Ocean
was such a surprise. If it had happened on land, it would have caused
massive devastation, but the effects, most likely, would have been
fairly local. Instead, the shock wave -- spreading from beneath
the ocean floor -- sent a giant bulge of water six miles above.
The ripple effect quickly spread, reaching Sri Lanka in two hours,
the coast of India in three hours and the eastern-most parts of
Africa in six.
means "harbour wave" in Japanese. Caused by an earthquake
beneath the sea floor, it is a series of waves that is caused by
it. Even though tsunamis are primarily associated with earthquakes
in oceanic and coastal regions, landslides, volcanic eruptions,
nuclear explosions, and even impacts of objects from outer space
(such as meteorites, asteroids, and comets) can also generate tsunamis.
It can drop 200 billion gallons of water on a shoreline in a minute.
say it is one of nature's most massive killers. Tsunamis are not
caused by the tides and are unrelated to the tides; although a tsunami
striking a coastal area is influenced by the tide level at the time
tsunami will lose little energy as it grows. Hence in very deep
water, it will travel at high speeds and great transoceanic distances
with limited energy loss. For example, when the ocean is 20,000
feet (6100 m) deep, unnoticed a tsunami travels about 550 miles
per hour (890 km/hr), the speed of a jet airplane. And it can move
from one side of the Pacific Ocean to the other side in less than
the Pacific Coast is deemed more liable to the most amount of tsunami
occurrences -- countries in the region have websites dedicated to
informing its residents on how to react in the event of any. As
a tsunami leaves the deep water of the open sea and spreads into
the more shallow waters near the coast, it undergoes a transformation.
Since the speed of the tsunami is related to the water depth, as
the depth of the water decreases, the speed of the tsunami diminishes.
change of total energy of the tsunami remains constant. Therefore,
the speed of the tsunami decreases as it enters shallower water,
and the height of the wave grows. Because of this "shoaling"
effect, a tsunami that was imperceptible in deep water may grow
to be several feet or more in height. In extreme cases, water level
can rise to more than 50 feet (15m) for tsunamis of distant origin
and over 100 feet (30m) for tsunami generated near the earthquake's
epicentre. One coastal area may see no damaging wave activity while
in another area destructive waves can be large and violent