For many inhabitants of the Earth, a tsunami threat looks like an abstract and very exotic danger. However, the vagaries of nature in recent years are such that it is quite difficult to feel completely protected from such a danger. Moreover, even in a small lake, under a certain confluence of circumstances, a large wave can arise. If it is about the cities located on the seashore or beside the ocean, the problem is urgent enough.
The knowledge of how to survive during a tsunami can be useful at the most unexpected moment and in almost any part of the globe. Therefore, it is essential to know how to anticipate the place and time of the occurrence of a tsunami and to determine which factors are the main in assessing the potential wave’s power and the speed at which it approaches the land.
Main Causes of Tsunami
The central and most frequent cause of tsunami occurrence is underwater earthquakes. Powerful jerks create a directional movement of huge masses of water that roll to the shore with waves more than 10 meters high and bring casualties and destruction. It is not surprising that the greatest risk of occurrence of this natural disaster exists in coastal areas with increased seismic activity. Thus, everyone knows the example of the tsunami in Japan in 2011, which led to an incredible number of human casualties and triggered an accident at the Fukushima-1 nuclear power plant (Ikehara et al. 2014).
Quite often, there is a tsunami threat in the Philippines, Indonesia, and other island states of the Pacific. The consequences of tsunamis can be very serious, and this danger should be discussed in detail since many people are exposed to it.
Ways to Recognize the Approach of a Tsunami in Advance
The first reason to take care of a tsunami threat is the announcement of increased seismic activity in the coastal area. Earthquakes are natural signals notifying about a possible runup of a tsunami. In case seismologists manage to predict earth tremors in advance, the residents of settlements on the coast should ensure their safety in order not to expose their lives to danger. According to Melgar and Bock (2015), such warnings are relevant even if the earthquake’s strength in the city is low because the epicenter can be in the sea. That is why the threat is very dangerous in coastal areas where people, as a rule, are in no way protected from such a natural disaster.
During the moments of increased tsunami threat, the authorities’ reports on radio and television should be carefully monitored. In most cases, the danger becomes known in a few hours, which gives residents the opportunity to timely react to it. As tsunami witnesses note, animals are especially sensitive to the approach of a giant wave. Long before the onset of danger, they are worried. Many wild animals and birds tend to leave the area in advance.
It is also possible to predict the approach of a tsunami in fifteen-twenty minutes judging by the changes of the coastline. At this moment, the water quickly recedes, the sound of the surf subsides, the normal regime of tides breaks. In some cases, unusual and untimely tides lasting from several minutes to half an hour can be observed. As Leonard and Bednarski (2014) note, the tsunami of 2012 in Haida Gwaii was accompanied by a drift of unusual objects: fragments of ice or, for example, coastal debris that is raised from the bottom by the movement of water. The runup of the wave is always accompanied by thundering sounds since the mass of water is very large, and at high speed, its movement creates a very perceptible noise.
Ways to Reduce the Risks of Tsunami Impacts
Modern technologies make it possible to predict not only the power of an upcoming tsunami but also an approximate time in which it will happen. The fact is that experts from the Japanese National Research Institute of Geophysics and Natural Disaster Prevention have developed a high-tech system that predicts these natural disasters. This unique project, as Lin et al. (2014) note, enables residents of the coastal areas to escape from a tsunami within twenty minutes after the alarm. This time will be enough to completely evacuate the area that is endangered and to save all the residents. There have not been severe disasters in Japan that could be similar to that in 2011, but if one happens, people are likely to be ready.
This system has already been launched and includes dozens of different detectors installed at one hundred and fifty points on the seabed along the Pacific coast of Japan from Hokkaido to Tokyo. Information from the sensors comes through the cable directly to the Japanese meteorological office. The development and construction of the system cost the Japanese budget several hundred million dollars. Nevertheless, today, scientists and rescuers will be able to learn about the earthquakes that took place under the water about twenty minutes earlier.
According to Riquelme et al. (2015, p. 6487), the primary idea of any work related to the ways of identification tsunamis is “to provide a tool for emergency response, trading off accuracy for speed”. The creation of a new system has become a new step in the development of science. It is quite easy to imagine how many lives can be saved by possessing the information that can be acquired with the help of those useful data that come from sensors located on the seabed.
Additional Ways to Predict Tsunami
In the middle of the twentieth century, after the catastrophic earthquake in Hawaii, the Pacific Tsunami Warning Service was established in the Pacific Ocean (Yeh & Mason 2014). Seismic stations record the time and place of the earthquake; if its epicenter lies under water, it is possible to expect a tsunami. In this case, all stations monitoring sea level are notified of the need to monitor the approach of big waves.
In order to calculate an approaching time, there are special maps of the duration of the tsunami run from various points to the Hawaiian Islands. The notification about the expected time of the approach of waves is transmitted via the international Pacific communication system. The headquarters of the Tsunami Warning Service (subordinate to the National Ocean Service of the National Oceanic and Atmospheric Administration) is in Honolulu.
Conclusion
Thus, it is significant to find out how to anticipate the place and time of the occurrence of a tsunami. Those factors that signal an imminent threat are always important to consider. Appropriate equipment was invented after the disastrous effects of the tsunami in Japan. Earthquakes, as a rule, are the most common reasons for the emergence of large waves.
Reference List
Ikehara, K, Irino, T, Usami, K, Jenkins, R, Omura, A & Ashi, J 2014, ‘Possible submarine tsunami deposits on the outer shelf of Sendai Bay, Japan resulting from the 2011 earthquake and tsunami off the Pacific coast of Tohoku’, Marine Geology, vol. 358, no. 1, pp. 120-127.
Leonard, LJ & Bednarski, JM 2014, ‘Field survey following the 28 October 2012 Haida Gwaii tsunami’, Pure and Applied Geophysics, vol. 171, no. 12, pp. 3467-3482.
Lin, JH, Cheng, CY, Yu, JL, Chen, YY & Chen, GY 2014, ‘Quick estimation of tsunami induced runup on coastal area’, Coastal Engineering Proceedings, vol. 1, no. 34, pp. 8-22.
Melgar, D & Bock, Y 2015, ‘Kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data’, Journal of Geophysical Research: Solid Earth, vol. 120, no. 5, pp. 3324-3349.
Riquelme, S, Fuentes, M, Hayes, GP & Campos, J 2015, ‘A rapid estimation of near-field tsunami runup’, Journal of Geophysical Research: Solid Earth, vol. 120, no. 9, pp. 6487-6500.
Yeh, H & Mason, HB 2014, ‘Sediment response to tsunami loading: mechanisms and estimates’, Géotechnique, vol. 64, no. 2, pp. 131-143.