Japanese researchers have warned that tsunamis can travel vast distances across oceans and return to coastlines days after an earthquake, posing risks even after official warnings are lifted.
According to an analysis by the Japan Meteorological Agency’s Meteorological Research Institute, a tsunami triggered by a magnitude 8.8 earthquake near Russia’s Kamchatka Peninsula last summer initially crossed the Pacific Ocean and reached the coast of South America, nearly 15,000 kilometers from the epicenter. The waves then rebounded off the South American coastline and traveled back toward Japan.
The rebound tsunami is believed to have reached Japan about 48 hours after the earthquake, a time when all tsunami warnings and advisories had already been lifted. Observations confirmed waves measuring up to 0.6 meters in parts of Ibaraki and Iwate prefectures on the morning of August 1.
The earthquake occurred at 8:24 a.m. on July 30, prompting tsunami warnings along the coasts of Tokyo and 12 other prefectures. Initial tsunami waves reached Japan the same day, with the highest waves of 1.4 meters recorded by July 31. Warnings were lifted by that evening.
Using a supercomputer and seabed pressure data from the Tohoku offshore observation network, researchers recreated the wave movements. The analysis showed that without the presence of the South American continent, the rebound tsunami could not be reproduced, highlighting the role of continental reflection in long-distance tsunami behavior.
Experts stressed that tsunamis traveling long distances have historically caused damage in Japan. They cited the 1960 Chile earthquake, when tsunami waves reached Japan after 22 hours and resulted in more than 100 deaths and missing persons.
“Tsunami can arrive much later than the first waves,” said Hiroaki Tsushima, chief researcher at the institute, urging the public to remain cautious and prepared even after advisories are lifted.
