Massive Quake, 30-Metre Tsunami May Hit Northern Japan: How These Events Are Predicted

Japan¡¯s government panel has revealed that Tsunamis as high as 30 metres could hit Hokkaido as well as Iwate in Nothern Japan if a magnitude 9 earthquake occurs near the sea trenches adjoining the Pacific coast.

Reuters

Experts have sounded the alarm based on a ¡®worst-case¡¯ scenario stating that an earthquake of magnitude 9 originating from Japan Trench and the Kuril Trench off northern parts of Japan could be ¡®imminent¡¯.

According to the Cabinet Office panel, even though it is difficult as of now to be certain that an earthquake of such a magnitude could occur, the region has experienced massive tsunamis every 300 to 400 years, the last one observed during the 17th century.

The panel ran simulations based on the analysis of tsunami deposits in the past 6000 years revealed damages to seven prefectures -- Hokkaido, Aomori, Iwate, Miyagi, Fukushima, Ibaraki and Chiba.

Surely, warnings like these indicate how unsafe the locations could be, in case such a devastating earthquake occurs. However, one might wonder how Japan keeps tabs on earthquakes and tsunamis, being one step ahead to warn its citizens in case things go south.

How are Tsunamis detected?

Japan is one of the most earthquake-prone areas in the world, and when there's an earthquake, there could be a tsunami. Oceans in the coastal areas of Japan are fitted with a plethora of devices that keep on feeding it the data it needs, in real-time to predict the occurrence of a tsunami.

Reuters

Japan has deployed tsunami sensors way off the shore, along with coastal area tsunami meters (to gauge the impact of tsunami waves at the coast).

NOAA

The system also involves broad-band seismometers for accurate earthquake readings. Along with this, it also harnesses data from DART systems -- Deep-ocean Assessment and Reporting of Tsunami -- along with tsunami buoys that feed data from under the water to the system. It uses the Iridium satellite to share information from the sea to the land.

Warnings and Information about Tsunamis

As soon as the first earthquake or tsunami is detected, the Japanese Meteorological Agency issues warnings within the first 3 minutes of its occurrence while ceasing public transport to prevent further damages.

Initial warnings don¡¯t really give the exact height for the tsunamis instead it categorizes them ¡°High¡± for waves between 1 and 3 meters, and ¡°Huge¡± for waves between 3 and 10 meters or even above 10 meters.

Post this they look for other data to give an accurate idea for what to expect -- including not just the height of the tsunami but also the ETA (Estimated time of arrival).

Reuters

Normally, 15 minutes after an earthquake, the tsunami information is issued in five classes, and JMA uses the upper-limit value for each class in the next warnings -- 1 m, 3 m, 5 m, 10 m and above 10 m.

In case the first waves observed are much smaller than the warning issued, JMA will issue ¡°Currently observing¡± announcements to keep people aware that it is still dangerous out there. On the other hand, if the waves are expected to be higher than estimated, the warnings will be shared immediately.