80-Centimeter Tsunami Following a 7.4-Magnitude Earthquake in Northern Japan

Japan’s Meteorological Agency (JMA) issued a tsunami warning for waves up to three meters (10 feet) after an earthquake with a magnitude of 7.4 rocked northern Japan on Monday.  The earthquake, which occurred in Pacific waters off northern Iwate prefecture at 4:53 p.m. (0753 GMT), was powerful enough to rock big structures hundreds of kilometers away in Tokyo.  According to the JMA, an 80-centimeter (31-inch) tsunami wave struck a port at Kuji, Iwate, some 40 minutes later.

“Evacuate immediately from coastal regions and riverside areas to a safer place such as high ground or an evacuation building,” it said, warning that damage due to tsunami waves was expected. “Tsunami waves are expected to hit repeatedly. Do not leave safe ground until the warning is lifted,” it said.

There was no immediate obvious damage near a number of ports in Iwate, according to footage from the national broadcaster NHK. In a televised news briefing, a JMA official issued a warning that other earthquakes might occur in the region. A crisis management team has been established, according to the prime minister’s office.

“For those of you who live in areas for which the warnings have been issued, please evacuate to higher, safer places such as higher ground,” Prime Minister Sanae Takaichi told reporters, adding that the government was trying to confirm whether there were any casualties or property damage.

Perched atop four major tectonic plates along the western edge of the Pacific “Ring of Fire,” Japan is one of the most seismically active nations in the world. The archipelago, which is home to roughly 125 million people, is responsible for about 18% of all earthquakes worldwide and usually receives 1,500 shocks annually.

Although the harm they do varies depending on their position and the depth below the Earth’s surface at which they impact, the great majority are moderate. The 2011 enormous 9.0-magnitude underwater earthquake that caused a disastrous meltdown at the Fukushima nuclear plant and a tsunami that killed almost 18,500 people haunts Japan.

A potential “megaquake” along the Nankai Trough prompted the JMA to publish its first special advisory in 2024.  The Philippine Sea oceanic tectonic plate is “subducting”—or gradually slipping—underneath the continental plate that Japan is situated atop in this 800-kilometer underwater trench.

According to the authorities, a tsunami and earthquake in the Nankai Trough could result in up to $2 trillion in damage and up to 298,000 fatalities. After a week, the JMA lifted the 2024 caution, but this caused vacationers to cancel hotel reservations and panic buy basics like rice. 

Following a magnitude-7.5 earthquake off the northern coast in December 2025, it issued a second “megaquake” advisory that lasted for a week. Although no significant damage was reported, the December 8 earthquake caused tsunami waves as high as 70 centimeters (28 inches) and injured over 40 persons.