Japan issued a special advisory on Monday, April 20, warning of an increased risk of earthquakes at magnitude 8.0 or stronger, after a powerful jolt rattled the country’s north and prompted a tsunami warning. The Japan Meteorological Agency (JMA) said in a statement that “the likelihood of a new, huge earthquake occurring is relatively higher than during normal times.” There were no immediate reports of serious injuries or significant damage, Chief Cabinet Secretary Minoru Kihara told a news conference.
The warning for the northern region came a few hours after a 7.7-magnitude earthquake struck the area, shaking large buildings in the capital Tokyo, hundreds of kilometres (miles) from the epicentre. The quake hit at 4:53 pm local time in Pacific waters off northern Iwate prefecture, Japan’s Meteorological Agency (JMA) said. Around 40 minutes later, an 80-centimeter tsunami wave hit a port in Kuji in Iwate, according to the JMA, which initially estimated the quake’s strength at 7.4 but later revised it upward.
“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. Footage from national broadcaster NHK did not show any immediate visible damage around several ports in Iwate.
A JMA official warned in a televised press briefing that more quakes could strike the area within the next week, particularly within the next two to three days, potentially “causing even stronger shaking.”
The prime minister’s office said it had set up a crisis management team. “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.
Japan is one of the world’s most seismically active countries, sitting on top of four major tectonic plates along the western edge of the Pacific “Ring of Fire.” The archipelago, home to around 125 million people, typically experiences around 1,500 jolts every year and accounts for about 18% of the world’s earthquakes. The vast majority are mild, although the damage they cause varies according to their location and the depth below the Earth’s surface at which they strike.
Japan is haunted by the memory of a massive 9.0-magnitude undersea quake in 2011, which triggered a tsunami that killed or left missing around 18,500 people and caused a devastating meltdown at the Fukushima nuclear plant.
In 2024, the JMA issued its first special advisory of a possible “megaquake” along the Nankai Trough. This 800-kilometer undersea trench is where the Philippine Sea oceanic tectonic plate is “subducting” – or slowly slipping – underneath the continental plate that Japan sits atop. The government has said a quake in the Nankai Trough and subsequent tsunami could kill as many as 298,000 people and cause up to $2 trillion in damage.
The JMA lifted the 2024 advisory after a week but it led to panic-buying of staples like rice and prompted holidaymakers to cancel hotel reservations. It issued a week-long second “megaquake” advisory in December 2025 after a magnitude-7.5 tremor struck off the northern coast. The December 8 quake triggered tsunami waves of up to 70 centimeters and injured more than 40 people, but no major damage was reported.
