What is a tsunami?

The term tsunami is generally used to refer to aa giant waveusually more than 15 meters high, which reaches the coast causing destruction and flooding.

How do tsunamis originate? The larger ones usually originate in ocean trenches and in 90% of cases due to earthquakes (the remaining 10% due to volcanic eruptions and geological faults).

They occur as a consequence of a shift of the seabed generally produced by the dislocation of the oceanic crust or by underwater earthquakes.

In tsunamis, the wave travels across the sea with speeds of the order of 900 m/s to 300 m/s and relatively small amplitudes, from one to a few meters. As you approach the coast, the depth of the water decreases and then increases.

In the most extreme cases, such as that of Indonesia in 2004 (the most devastating of the century), the waves can reach 30 meters high. The places most frequently affected by tsunamis are, in addition to Indonesia, United States of America (Alaska and Hawaii), Canada, kilos, Sri Lanka, Thailand, India AND Japan.

The word comes from the sum of two Japanese terms: tsu (“port” or “bay”) e Nami (“wave”). It is no coincidence that it derives from that language, since Japan is one of the countries in the world most prone to suffering from it.

“Tsunami” began to be officially accepted thanks to the seismologist Beno Gutenberg. In 1961, a year after his death, the International Scientific Community authorized it.

Tsunami warning in Japan

This Monday, two earthquakes, one of magnitude 7.5, hit the central-western coast of Japan and caused at least 6 deaths due to landslides and damage to houses.

More than 51,000 people in five Japanese prefectures have received evacuation orders, as there was also a tsunami warning.

This was reported by the American Geophysical Institute (USGS) which initially spoke of an intensity of 7.4 in the first earthquake, although it later increased it.

Japanese authorities have warned that the first earthquake could cause tsunami waves up to five meters high along the western coast of the country, within a radius of 300 kilometers from the epicenter of the earthquake.

“Hazardous tsunami waves generated by this earthquake are possible within 300 kilometers of the epicenter along the coast of Japan,” the Hawaii-based Pacific Tsunami Warning Center agreed.

The Japan Meteorological Agency (JMA) warned that waves could reach a height of five meters. The second earthquake occurred not far from the epicenter of the first. Both earthquakes were recorded in Ishikawa Prefecture, at a depth of 10 kilometers.

Sources: Argentina.gob – National Institute for Seismic Prevention/ANSA