Tsunami Warning System
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IN the early hours of 26th December 2004 the world witnessed one of the most devastating natural disasters in the recent times causing the death of nearly 80,000people.Tsunami-a powerful fast moving wave by an under sea disturbance.If we had sufficient warning system to give indications ,then we certainly could avoid this much of destruction. With the present technology, even a slight undersea disturbance can be detected by special detectors placed on the sea floor.These signals are picked by the surface buoy, which sends data to satellite for further distribution to ground stations.
What is Tsunami?
Tsunami is a Japanese word represented by two words, Tsu-harbor, Nami-wave means a destructive, Ocean riding, gigantic wave created by an under sea disturbance.
More than a quarter of all reliably reported Pacific tsunamis since 1895 originated near Japan. This is not surprising, because Japan is precariously situated near the colliding margins of four tectonic plates. Recognizing the recurring threat, the Japanese have invested heavily over the years in tsunami hazard mitigation, including comprehensive educational and public outreach programs, an effective warning system, shoreline barrier forests, seawalls and other coastal fortifications.
Propagation of the tsunami transports seismic energy away from the earthquake site through undulations of the water, just as shaking moves the energy through the earth. At this point, the wave height is so small compared with both the wavelength and the water depth that researchers apply linear wave theory, which assumes that the height itself does not affect the wave's behavior. The theory predicts that the deeper the water and the longer the wave, the faster the tsunami. This dependence of wave speed on water depth means that refraction by bumps and grooves on the seafloor can shift the wave's direction, especially as it travels into shallow water. In particular, wave fronts tend to align parallel to the shoreline so that they wrap around a protruding headland before smashing into it with greatly focused incident energy. At the same time, each individual wave must also slow down because of the decreasing water depth, so they begin to overtake one another, decreasing the distance between them in a process called shoaling. Refraction and shoaling squeeze the same amount of energy into a smaller volume of water, creating higher waves and faster currents.
The tsunami can be actually generated by any disturbance that displaces a large mass of sea water from its equilibrium position. Violent volcanic eruptions, which causes sudden
displacement of a large volume of sea water, can also give Rise to destructive tsunami waves. One of the largest and most destructive tsunamis ever recorded was generated
on august 26, 1983 after the explosion of the volcano of krakatoa in Indonesia.
Tsunami waves are also generated due to displacement of sea water resulting from rock falls, icefalls and sudden land slides. For example in 1980’s construction work of
an air port runs way along the cost of Southern France,triggered an under water land slide, which generated destructive tsunami waves in the harbor of Thebes.
Similarly, when massive earth quakes occur, there are high chances of the occurrence of under water landslides that may contribute to tsunami generation. These waves
rapidly travel away from the source due to dissipation of energy, and create havoc in the near by coast lines.
How we can predict it?
For people living near the coast, the shaking of the ground is sufficient
warning for an impending tsunami. A noticeable rapid raise or fall in coastal waters is also a sign that a tsunami is approaching. Some tribals in Andaman like Centenaries, Shanghais, Ongeys, Jaravas can predict these tsunamis by hearing different sounds made by the birds.
With advances in technology, it is possible to predict the occurrence of tsunamis. With computer technology it can be known in advance how high tsunami waves will be along the coast for different kinds of earth quakes. When put on maps, these predictions can guide people to evacuate the areas to be hit by tsunamis.
What is the warning system?
The key element to tsunami hazard mitigation is a tsunami warning system. But regardless of how sophisticated a warning system may be all it can do is issue a warning. The effectiveness of the system is judged by what Civil Defense Agencies do with a warning. These agencies must have an effective Operational and Emergency Preparedness Plan to act on the warning and disseminate it rapidly and effectively to the public. This can be done only if there is an established operating plan designating infrastructural communications and responsibilities. This system monitors sea movements and can e used to map the path of Tsunamis and estimates the rate of approach.
How a warning system works?
A Tsunami warning system comprises a network of seismometers tide gauges with proper communication systems. The seismographs will estimate the strength and location of an earthquake whereas tide gauges near the epicenter of an earth quake.
This system comprises of a seafloor bottom pressure recording (BPR) system capable of detecting Tsunamis as small as 1cm, which sends signals to a surface buoy anchored to it. This device basically senses pressure differences caused due to the movement of Tsunami waves. Normal wind waves which have much shorter period than Tsunamis are filtered out. If a tsunami is detected data is uploaded from an onboard computer chip, via sound signals to a hydrophone that is attached to the surface buoy. The buoy further sends the data to the geo stationary operational environmental satellite, orbiting our planet. The information is then down loaded to ground based computers, which demodulate the signals for immediate dissemination to NAOAA’s Tsunami warning centers. India is al set to install a similar Tsunami warning system in the Indian Ocean called the “Deep Ocean Assessment and Reporting system (DOASRS).
If India already implanted the warning center –Deep Ocean Assessment and Reporting System(DOASRS) for the pathetic disaters especially like this “Tsunami”,we can avoid the distruction befor hand.