Tsunami – Concept, how it occurs and Japan tsunami

We explain what a tsunami is and how this oceanic phenomenon occurs. Also, the Japan tsunami and what is an earthquake.

Tsunamis are the consequence of an underwater seismic movement.

What is a tsunami?

Tsunami is a term from Japanese (tsu, “Port or bay” + nami, “Wave”), synonym of tidal wave (from Latin: mare, “Sea” + motus, “Movement”), and with both a complex oceanic phenomenon is described, characterized by waves of great size and energy, which mobilize gigantic amounts of water, reaching the mainland and destroying everything in its path.

Tsunamis should not be confused with other maritime movements such as tidal waves, tides or floods as a result of storms, storms, hurricanes or tropical storms. Tsunamis are not generated by the action of the wind, as in those cases, but rather as consequence of an underwater seismic movement, an underwater earthquake.

Tsunamis have enormous destructive capabilities and are generally, along with fires and landslides, some of the biggest concerns after a major earthquake. Because tsunami warning is usually given immediately after a quake or earthquake ends whose epicenter is in the ocean or in a coastal location.

The area of ​​the world with the highest frequency of tsunamis on the planet It is in the Pacific Ocean: the so-called “ring 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, The Philippines, Guatemala, Honduras, Indonesia, Japan, Malaysia, Mexico, Nicaragua, Panama, Papua New Guinea, Peru, Russia, Samoa, Singapore, Taiwan, East Timor, and Tonga, as well as the Aleutian Islands, the Solomon Islands.

How does a tsunami occur?

As we have said, a tsunami is the direct consequence of an underwater earthquake, whose telluric waves are transmitted to the water and are magnified enough to generate a gigantic wave. A minimum unevenness of the seabed is enough for this, since the enormous mass of oceanic water moves and, when it regains its balance, generates a marine wave with enough energy to travel kilometers in a very short time.

These waves are practically invisible in the high seas, until they reach shallower waters. There they must lose speed thanks to the friction with the sea floor, compensating however with height: the result is a sequence of colossal waves breaking on the shore and that flood the mainland.

Japan tsunami

Japan tsunami
The 2011 earthquake in Japan created tidal waves up to 40.5 meters high.

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 in the sea, off the coast of Honshu, Japan, at a depth of 32 kilometers, and it occurred at 2:46 pm (local time), lasting approximately 6 minutes. Immediately after the earthquake there were two or three aftershocks of more than 7 points of intensity, and later about 1230 smaller aftershocks.

In the incident some 15,893 people died, about 6,152 were injured and about 2556 disappeared in total. It is the largest earthquake suffered by Japan so far and the fourth largest recorded in the entire world.

Tsunami and earthquake

Tsunami are, as we have seen, consequences of an earthquake. Nevertheless, 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 tend to collide, push or strain, generating vibrations that are transmitted along its surface, maximizing as they advance outwards.

They can be some of the most catastrophic and unpredictable natural phenomena known to mankind.