P.Manikiran, D.B.Rajesh,3rd year,E.C.E., 3rd year,E.C.E.,B.V.C.Engg.College, B.V.C.Engg.College,Odalarevu. Odalarevu.

ABSTRACT:- IN the early hours of 26 th 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.

Introduction:-. 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.

What is the root of this pathetic disaster?1) Undersea earth quakes.2) Volcanic eruptions.3) Land slides.

Undersea earth quakes:- The earth’s outer surface is broken in to pieces called tectonic plates. Earth quakes

usually occur in regions of the earth along tectonic plate boundaries called faults, where different tectonic plates meet. The chances of occurring of earth quakes are very high in these regions due to the collision of these plates as these plates are constantly moving past each other.Due to this collision a large amount of stress is released.Infact80% of all recorded earth quakes occur around the edge of The pacific plate, including New Zealand, Papua, New Guinea,Japan, Canada, USA and South Africa. Those Tsunamis are

Powerful that occurs at a depth shallower than 50Kms with an epicenter near or on the ocean floor. If the sea floor Movement is horizontal, a tsunami is not generated. The Generation of these tsunami waves depends on the nature and degree of the displacements of the sea water column. It is only the vertical displacement of sea water due to abrupt, jerky movement of fault blocks on the seabed that invite the wrath of nature and gives birth to powerful tsunamis.

Volcanic eruption:-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.

Landslides:-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.

Our international cooperative efforts to mitigate the tsunami disaster started over 25 years ago, long before the Decade was proclaimed, and that tsunami is probably the only disaster that has been dealt so effectively on an international scale. This has been made possible through the leadership of IOC in forming the ITSU group.An area where international cooperation will prove to be most valuable will be in the further development of tsunami evaluation and prediction capability using current technology of satellite data telemetry and communications, and use of microcomputers. Adequate state of the art seismic and water level instrumentation, rapid telemetry and telecommunications are needed, both for data acquisition and for warning dissemination. These are the most important components for an effective national or regional Tsunami Warning System. The Pacific Tsunami Warning System presently makes use of an extensive seismic and water level instrumentation network that has been made possible through the generous support of member nations of ITSU, through cooperative programs between many agencies and national governments, and through programs such as the International Tropical Ocean Global Atmosphere (TOGA) Sea Level Program

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. This comprises hundreds of seismic monitoring stations world wide as well as coastal tide gauges, besides sophisticated deep ocean assessment and reporting of

tsunamis (DART) buoys in the pacific basin capable of detecting even a centimeter’s difference in the ocean height. Such warning system saved many lives in Honolulu in 1952 when an approaching Tsunami was detected. Supported by 54 countries the European communication and 34 international organizations, a global earth observational system is being developed, which over the next decade will revolutionize the understanding of earth. One of the major areas of focus of this US-led initiative would be weather forecasting and reducing damage caused by national disasters.India is al set to install a similar tsunami warning centre in the Indian Ocean called the Deep Ocean assessment and reporting system (DOASRS)

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).

What and where these centres located?As part of an international cooperative effort to save lives and protect property, the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service operates two tsunami warning centers. The Alaska Tsunami Warning Center (ATWC) in Palmer, Alaska, serves as the regional Tsunami Warning Center for Alaska, British Columbia, Washington, Oregon, and California.The Pacific Tsunami Warning Center in Ewa Beach, Hawaii, serves as the regional Tsunami Warning Center for Hawaii and as a national/international warning center for tsunamis that pose a Pacific-wide threat. Conclusion: -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.

References:-1)Science reporter ,Feb’2005.2)www.frontlineonnet.com3)www.geophys.washington.edu/tsunami4)www.web.ask.com/redir5)www.science.sakhalin.org