Tohoku University institute analyzes huge tsunamis over past 400 years


Tohoku University’s International Research Institute of Disaster Science has released a report analyzing major tsunamis across the globe over the past 400 years in a bid to raise awareness about tsunami hazards.

The report, published late last month ahead of the first World Tsunami Awareness Day last Saturday, was created by the United Nations based on a proposal by Japan.

“Comparisons between tsunami height and wave force show that only using the tsunami height might underestimate the building damage,” the report said, calling for better countermeasures against tsunami.

The report analyzed 94 tsunamis caused by earthquakes with magnitudes of over 7.5 and estimated fault models, in order to assess how tsunami waves have spread, their heights, strengths and arrival times, among other details.

Of the tsunamis covered by the report, those that occurred recently include the March 2011 tsunami that devastated coastal areas in the Tohoku region following a 9.0-magnitude earthquake.

Another is the 2004 Indian Ocean tsunami, which was triggered by a 9.1-magnitude quake off Sumatra, Indonesia. It had a maximum height of 50.9 meters and killed 227,899 people.

The report also covered the 1755 earthquake in Lisbon, Portugal, with a magnitude of 8.5 that triggered a maximum tsunami wave of 18.3 meters and left over 50,000 people dead.

According to Fumihiko Imamura, head of the institute and professor of tsunami engineering at the university, an 11-year-old girl who was with her family in Phuket, Thailand, when the Indian Ocean tsunami happened, recognized that tsunami waves would come because she noticed sudden backwash currents, a sign of tsunami she learned in school.

After informing her parents and others nearby of a possible tsunami risk, she is believed to have saved the lives of over 100 people who may have been killed, according to Imamura.

Imamura highlighted the importance of making preparations for tsunami risks based on the lessons from the March 2011 tsunami in northeastern Japan, in which many people died due to their failure to escape.

“Unlike the March 2011 disaster, tsunami waves are expected to arrive soon after a powerful earthquake that could occur directly beneath Tokyo or a strong quake that is seen occurring at the Nankai Trough” off Japan’s central to southwestern Pacific coasts, he said.