Tsunami Can Travel Vast Distances Before Striking, Warn Japanese Researchers

The Yomiuri Shimbun

21:01 JST, January 6, 2026

Tsunami caused by the magnitude 8.8 quake that struck near Russia’s Kamchatka Peninsula last summer likely rebounded off South America and reached Japan about 48 hours later, according to analysis by the Japan Meteorological Agency’s research institute.

Tsunami that travel long distances before reaching Japan have been known to cause damage in many cases. Experts urge the public to be aware of the risks.

Last summer’s quake occurred at 8:24 a.m. on July 30. The Meteorological Agency issued tsunami warnings and advisories along the coasts of Tokyo and 12 other prefectures. Tsunami reached Japan that same day, and the highest waves, up to 1.4 meters tall, arrived by July 31. All tsunami warnings and advisories were lifted by the evening of July 31.

The Meteorological Research Institute reproduced wave movements with a supercomputer, using data on water pressure captured in the seabed observation network off the Tohoku region.

The analysis showed that tsunami initially traveled across the Pacific Ocean and reached the coast of South America, about 15,000 kilometers away from the quake’s epicenter. The waves then bounced off the coast and traveled back toward Japan via the Pacific.

The rebound tsunami are projected to have reached Japan about 48 hours after the earthquake, when tsunami warnings and advisories had been lifted. In fact, 0.6-meter-high waves were observed in Kamisu, Ibaraki Prefecture, and Kuji, Iwate Prefecture, in the morning of Aug. 1. The agency found that the tsunami could not be reproduced in an analysis that assumed there was no South American continent, only ocean.

Tsunami advisories are issued when waves are projected to be at least 0.2 meters high and are expected to cause damage.

“At that time, the public was fully aware that tsunami had been observed. As we concluded that there was no risk of damage, we did not issue another advisory,” a Meteorological Agency official said.

In 1960, a tsunami caused by a magnitude 9.5 earthquake off the coast of Chile reached Japan in about 22 hours and left more than 100 people dead or missing.

“Tsunami can arrive far later than the first tsunami waves,” said Hiroaki Tsushima, a chief researcher at the Meteorological Research Institute. “The public should be more aware when it comes to disasters and be prepared for a similar earthquake.”