Warning Systems and Prevention Techniques of Tsunamis

Tsunamis are series of ocean waves caused by underwater seismic activity or volcanic activity. Several countries all around the world are being affected by this type of natural disaster and even though usually small tsunamis do not cause much damage, the giant waves are a threat.

A tsunami while reaching the shore full of people. http://www.positivestart.org/images/china_2002_wave_350.jpgThe tsunami from December 2004 was generated by a 9.1 magnitude earthquake and its waves devastated the Indian Ocean region as well as some parts of South-East Asia causing the death of around 230,000 people. As tsunamis are a natural disaster, we cannot prevent them but we can use early warning systems and community preparedness to minimize the effects and destruction. In response to the 2004 disaster, the National Oceanic and Atmosphere Administration (NOAA) along with the United Nations Intergovernmental Oceanographic Commission began to cooperate and established Tsunami Warning Systems (TWS) in the areas of the world where the tsunami occurred, while the NOAA’s Pacific Tsunami Center and the Japan Meteorological Agency provided warnings to countries all over the world.

A Tsunami Warning System (TWS) is a system which is supposed to detect the tsunami and send out warnings to places that are in danger to prevent the loss of many human lives as well as loss of property. The TWS has a tsunami detecting network of sensors and an alarming system which provides time to evacuate the coastal areas and other areas that are in risk of being hit by the wave. The warning systems have sensors which pick up seismic waves and the earthquake is immediately detected by seismologists because the seismic waves travel with the speed of 14,400 km/h, which gives time for possible tsunami warning because the waves travel with the speed of 500-1000 km/h in open water. However, this system is unable to predict if the earthquake generated a significant tsunami and this way there are more false alarms than actual verified warnings. When the sensors detect an earthquake, they automatically send out signals and after observing the sea level height with shore-based tide gauges the existence of a tsunami is verified.

A diagram of how a tsunami is triggered by an earthquake. In order to be able limit losses and human victims caused by a tsunami, inhabitants of coasts must realize what is exposed to these attacks of waves and be aware of the threat and react to it appropriately. In order to do this there is a need for a tsunami early warning system. In the early 90’s two American organizations: National Oceanic and Atmospheric Administration (NOAA) and the Federal Emergency Agency FEMA have financed the project of creating a scenario of an earthquake in northern California and maps potentially flooded places of cities Eureka and the city of Crescent. The map they managed to create was emerged to show all threat and it was the first of its kind in the USA. It appoints receptive areas that are in danger of being flooded by a tsunami as well as areas that are exposed to seismic activity and landslips.

Presently NOAA polishes up a network of deep sea signaling stations which will pick up a tsunami signals and will report about them immediately. This project is called the Deep-Ocean Assessment and Reporting of Tsunamis (DART). The tsunami warning system consists of a network of seismographs that send the results of measurements as soon as possible to the warning center. Forthcoming signals are analyzed incessantly, if an earthquake takes a place, the program defines its localization (the geographic coordinates, its depth), its magnitude (amount of released energy) and initial parameters generated by the tsunami. If the energy of the potential tsunami surpasses a certain threshold, further modulations are made. The time for the tsunami to reach the closest sections of the coast is predicted and the height of the wave when reaching the shore is predicted.

If this height exceeds over the conceded safe height of the waves, the program automatically sends alerts and warnings to proper services in a certain region which provide the information of the predicted time and height of the tsunami until it reaches a certain place on the coastline. Despite all these technological developments even the most reliable warning system will not be successful without the effective reaction from the citizens. The coast’s residents and tourists must be able to recognize the phenomenon of a tsunami as a natural disaster. Those people must especially beware of earthquakes that could possibly generate a tsunami and in case of an emergency be able to quickly evacuate to higher located areas. The coastal communities should own maps of potential floods in order to previously direct and guideline escape route. It is impossible to run away from a tsunami when you already see it on the horizon, and escaping is the only way to survive when the big waves come.

The warning system is made up of automatic stations on the surface of the water as well as deep-sea stations placed on the ocean floor which measure the pressure. The level of the ocean water is gauged with the accuracy of 5 cm. The data from the GEOS satellite is supplied to the warning center and later on automatically analyzed. In case of exceeding over the level of the acceptable standards, the potential risk of danger is announced to convenient services. The DART system has a purpose of decreasing the number of victims, minimizing the loss of property and destruction, as well as eliminating false alarms. The informing action of how to behave during and after an earthquake and what to do when there is a tsunami wave approaching is led mainly in Japan. This action was already successful enough to minimize the number of people killed by such a natural disaster.

An NOAA tsunami sensor on the surface of the water. http://www.noaanews.noaa.gov/stories2008/images/dart2.jpgThese systems are surely very effective but, as mentioned before, as long as people are not aware of the threat, there will be no use to any warnings. Also the warning might fail if there is any delay from the time when the sensors are triggered until the time the people in a certain community get the alert. Another problem could be the expenses of applying such a system to life. Many minor countries cannot afford it and therefore they suffer in several different ways in case of a tsunami.

If a nation cannot provide a security system for itself, it affects all areas of living conditions in that place. All housing would have to be placed high in the mountains instead of on the low plains and coastlines. The bigger problem would appear on small flat islands where it is impossible to escape to a higher place in case of an emergency. Unfortunately, even though early warning systems would be the only way to keep those places safe and give people time to leave the island, the governments are usually poor and cannot afford any kind of warning system. The events of December 26, 2004 are a reminder to all of us that tsunamis are an extremely devastating kind of natural disaster. It is a wake-up call and a lesson for everyone that we have to be able to more carefully prepare for tsunamis.

Bibliography

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