We explain what a tsunami is and how this oceanic phenomenon occurs. In addition, the tsunami of Japan and what is an earthquake.
What is a tsunami?
Tsunami is a term from the Japanese ( tsu , “port or bay” + nami , “wave”), synonymous with tidal wave (from Latin: mare , “sea” + motus , “movement”), and with both a described complex oceanic phenomenon, characterized by waves of great size and energy , which mobilize gigantic amounts of water , getting into the mainland and sweeping everything in its path.
Do not confuse tsunamis with other maritime movements such as tidal waves, tides or floods caused by storms, storms, hurricanes or tropical storms. Tsunamis are not generated by wind action, as in those cases, but as a consequence of an underwater seismic movement , an underwater earthquake.
Tsunamis possess enormous destructive capacity and are usually, along with fires and landslides, some of the greatest concerns after an earthquake of considerable magnitude. That is why tsunami is usually alert immediately after an earthquake or earthquake whose epicenter is in the ocean or in a coastal town.
The world’s most frequent area of tsunamis on the planet is in the Pacific Ocean: the so-called “belt of fire” of great seismic and volcanic activity, which covers part of the territories of Argentina, Bolivia, Brunei, Canada, Chile, Colombia , Costa Rica, Ecuador, El Salvador, United States, Philippines, Guatemala, Honduras, Indonesia, Japan, Malaysia, Mexico, Nicaragua, Panama, Papua New Guinea, Peru, Russia, Samoa, Singapore, Taiwan, East Timor and Tonga, as well like the Aleutian Islands, Solomon Islands.
How does a tsunami occur?
As we have said, a tsunami is a direct consequence of an underwater tremor, whose telluric waves are transmitted to the water and magnified enough to generate a gigantic wave. A minimum slope of the seabed suffices for this, because the enormous mass of oceanic water moves and, when recovering its balance, generates a sea wave with enough energy to travel kilometers in a very short time.
These waves are virtually invisible on the high seas, until they reach shallower waters. There they must lose speed thanks to friction with the sea floor , however compensating it with height: the result is a sequence of colossal waves that break on the coast and flood the mainland.
Causes of a tsunami
Tidal waves are the product, just like earthquakes, of the displacements of tectonic plates below the earth’s crust . Such movements often lead them to collide, confront, and change their shape, generating a friction whose energy is transmitted in the form of vibration, in this case, to the waters.
Similarly, tsunamis are due 90% to tidal waves, or to earthquakes that occur very close to the coast. Other possible causes of a tsunami are the explosion of submarine volcanoes or the impact on the sea of large meteorites .
Consequences of a tsunami
We have already mentioned the primordial and most feared consequence of the tsunamis: the tsunamis. The destructive capacity of gigantic and fast waves are widely feared in the coastal populations of the Pacific Ocean, and they have been proven time and again in their history of natural disasters.
On the other hand, tidal waves themselves can induce momentary or permanent changes in the distribution of ocean currents, or even in the flora and fauna of the seabed.
Japan tsunami
In 2011, Japan was the scene of one of the most violent tsunamis known in contemporary times . This phenomenon was part of the so-called Pacific Coast Earthquake in the Töhoku Region of 2011 (according to the Japan meteorological agency), which was particularly disastrous for the Asian nation.
This earthquake had an intensity of 9.0 Mw and created tidal waves up to 40.5 meters high . Its epicenter was located at sea, off the coast of Honshu, Japan, at a depth of 32 kilometers, and occurred at 2:46 pm (local time), lasting approximately 6 minutes. Immediately after the tremor there were two or three aftershocks of more than 7 intensity points, and then about 1230 minor aftershocks.
In the incident about 15,893 people died , about 6,152 were injured and about 2556 disappeared in total. It is the largest earthquake in Japan so far and the fourth largest in the world.
Tsunami and earthquake
The tsunami are, as we have seen, consequences of an earthquake. However, not all earthquakes necessarily produce tsunamis .
An earthquake is, fundamentally, a sudden movement of the tectonic plates of the earth’s surface, which when rearranging their position usually collide, push or tense, generating vibrations that are transmitted along its surface, maximizing as they move outward.
They may be some of the most catastrophic and unpredictable natural phenomena known to mankind.
