Japan earthquake live: Powerful aftershocks strike Japan days after megaquake advisory issued
Monday night’s earthquake injured at least 51 people
Japan has recorded a series of powerful aftershocks in the past several hours, including a magnitude 5.7 earthquake near the east coast of Honshu and a 4.9 earthquake in the Hokkaido region shortly after.
Two smaller quakes, of magnitudes 3.2 and 3, were also detected near the southern coast of Honshu.
On Tuesday, Japan’s weather agency issued its highest-level warning that a megaquake could follow Monday’s powerful tremor.
The warning covers approximately 800 miles (1,300 kilometres), stretching from Japan’s northeastern coast from Chiba, just east of Tokyo, to Hokkaido.
Monday night’s earthquake injured at least 51 people, according to the Fire and Disaster Management Agency. It also triggered widespread tsunami warnings, with waves of up to 70cm reported in several coastal communities.
The quake struck at around 11.15pm in the Pacific Ocean, roughly 50 miles off the coast of Aomori.
Tuesday’s notice was the first time this top-tier alert has been issued since the warning system was launched in 2022.
Understanding Japan’s seismic activity and megaquake advisory
Japan sits at the junction of several tectonic plates, making it one of the most seismically active regions in the world.
While earthquakes are common, some of the most powerful and dangerous ones originate from ocean trenches.
Monday’s magnitude-7.5 earthquake in northern Japan has brought attention back to the Japan Trench and the Chishima Trench.
A trench earthquake occurs along a deep crack in the ocean floor, called a trench, where one tectonic plate slides beneath another in a process known as subduction.
Over years or decades, stress builds as the plates get stuck.
When that stress is suddenly released, it can produce a powerful megathrust earthquake.
Because these earthquakes occur under the ocean, they often generate tsunamis, which can be extremely large and destructive.
The Japan Trench, off the east coast of Honshu, and the Chishima Trench, off northern Hokkaido and stretching toward the Kuril Islands, are key locations for these events.
These trenches have produced some of Japan’s most devastating earthquakes, including the 2011 Tohoku earthquake, a magnitude 9.0 megathrust quake that triggered massive tsunamis along the coast.
Historical patterns show that magnitude-7 or higher quakes in these regions can be followed by even larger earthquakes, according to the Japanese Meteorological Agency (JMA).
This is why Japan established a megaquake advisory system – a special alert to warn residents of northern Japan when the risk of a major trench-type earthquake and tsunami is elevated.
Megaquake advisory remains in effect
Authorities have confirmed that the megaquake advisory remains in effect following Monday’s earthquake in northern Japan.
Multiple powerful aftershocks have also rocked Japan in the two days since, although none on a par with Monday night's 7.5-magnitude tremor.
Residents and travellers in affected areas have been urged to stay vigilant, follow official guidance, and monitor updates from the Japan Meteorological Agency.
The megaquake advisory is in effect until 16 December. Officials estimate there is a one in 100 chance of the “big one” – an earthquake of magnitude 8 or higher – striking.
Citizens across 182 municipalities in seven prefectures along the Pacific coast, ranging from Hokkaido in the north down to Chiba Prefecture, have been asked to stay vigilant and keep megaquake grab-and-go emergency kits ready in case of any emergency.
Safety recommendations for residents and travellers
People in Hokkaido, Tohoku, and Pacific coastal areas from Hokkaido to Chiba – where a megaquake advisory is in effect – have been advised by the authorities to:
- Stay away from coastal areas
- Check evacuation routes and nearby shelters
- Prepare emergency supplies (water, food, portable toilet, lights, chargers)
- Secure furniture and household items to prevent injuries
- Follow updates from local governments, JMA, and official emergency channels
Japanese weather agency issues updated safety advisory
The Japan Meteorological Agency (JMA) has issued updated guidance after the recent magnitude 7.5 earthquake in northern Japan.
JMA warned that in regions that felt strong shaking, the chances of house collapses and landslides have increased.
Residents have been urged to avoid dangerous locations like coastal areas unless necessary, monitor seismic activity and rainfall, and follow updates from local authorities.
JMA also warned that strong aftershocks – potentially up to shindo 6+ (Japanese earthquake intensity scale that runs from 0 to 7) may occur for about a week, with the highest risk in the first two to three days.
JMA says that till midnight Tuesday, residents in affected areas are asked to take special preparations, reaffirm their usual disaster readiness, check supplies, and confirm evacuation routes.
Mapped: Japan aftershocks after 7.5-magnitude earthquake
Japan has experienced a series of aftershocks following Monday night’s powerful earthquake off the coast of Aomori.
The initial quake, which struck around 11.15pm, about 50 miles offshore, injured at least 51 people and triggered tsunami warnings, with waves reported up to 70cm.
Since then, more than a dozen aftershocks have struck, ranging in magnitude from 1 to 6.4. A magnitude 6.4 earthquake struck off eastern Aomori Prefecture at 3.22pm local time on Tuesday.
Yesterday, a magnitude 5.7 aftershock hit near the east coast of Honshu, followed by a 4.9 quake in Hokkaido.
Smaller tremors of magnitudes 3.2 and 3 were also detected near the southern coast of Honshu.
Care facilities unsure how to respond in case of an emergency as megaquake advisory remains in effect
Japan issued its first-ever megaquake advisory for 182 municipalities along the Pacific coast, urging residents to be prepared to evacuate immediately if strong shaking occurs.
The advisory has left some care facilities unsure of how to respond to the unprecedented situation, the Japan Times reported.
The newspaper noted some facilities, like a nursing home in Misawa, are well-prepared, having secured furniture, rechecked evacuation routes, and stocked up on supplies.
But others, like a facility for people with intellectual disabilities in Urakawa, expressed concerns about their evacuation capabilities, particularly given the high level of individual care required for residents.
“Each person needs individual care, and we don’t have the manpower to evacuate everyone at once,” the director of the facility was quoted as saying by the outlet.
“I honestly don’t know what measures we’re supposed to take, or how far we need to go.”
A director at a nursing home in Chiba Prefecture also said that the new advisory was unfamiliar, despite regular evacuation drills and emergency preparedness measures.
“Being prepared is everything,” the unidentified person was quoted as saying.
What might happen if a major trench earthquake strikes
The Japanese authorities have put in place a megaquake advisory after a magnitude-7.5 earthquake struck northern Japan.
It warns that the chances of a huge earthquake of magnitude 8 or higher are greater for roughly a week after Monday night’s sizeable tremor.
A post on the Japan Meteorological Agency website provides some projections for what the impact might be if a particularly large megaquake strikes an ocean trench off Japan.
It says a megaquake of the highest class is an extremely rare event, occurring “once every thousand years or even less frequently”.
The damage and casualties caused would vary depending on the season, time of day, and weather conditions.
The forecasts show that Hokkaido could face tsunamis between 10 and 20 metres, with Erimo Town possibly seeing nearly 30 metres.
Western Hokkaido areas like Tomakomai and Hakodate might get around 10 metres.
In Aomori, Hachinohe could experience tsunamis over 25 metres, while the Pacific coasts of Iwate, Miyagi, and Fukushima might see 10–30 metres.
The strongest shaking is expected in Hokkaido, with Akkeshi Town possibly reaching intensity 7 (on the Japan earthquake intensity scale), and areas east of Erimo reaching 6+.
Northern Honshu, including the Pacific coasts of Aomori and southern Iwate, could also feel 6+ intensity shaking.
Understanding Japan’s seismic activity and megaquake advisory
Japan sits at the junction of several tectonic plates, making it one of the most seismically active regions in the world.
While earthquakes are common, some of the most powerful and dangerous ones originate from ocean trenches.
Monday’s magnitude-7.5 earthquake in northern Japan has brought attention back to the Japan Trench and the Chishima Trench.
A trench earthquake occurs along a deep crack in the ocean floor, called a trench, where one tectonic plate slides beneath another in a process known as subduction.
Over years or decades, stress builds as the plates get stuck.
When that stress is suddenly released, it can produce a powerful megathrust earthquake.
Because these earthquakes occur under the ocean, they often generate tsunamis, which can be extremely large and destructive.
The Japan Trench, off the east coast of Honshu, and the Chishima Trench, off northern Hokkaido and stretching toward the Kuril Islands, are key locations for these events.
These trenches have produced some of Japan’s most devastating earthquakes, including the 2011 Tohoku earthquake, a magnitude 9.0 megathrust quake that triggered massive tsunamis along the coast.
Historical patterns show that magnitude-7 or higher quakes in these regions can be followed by even larger earthquakes, according to the Japanese Meteorological Agency (JMA).
This is why Japan established a megaquake advisory system – a special alert to warn residents of northern Japan when the risk of a major trench-type earthquake and tsunami is elevated.
Japan’s earthquake, aftershocks and ‘megaquake’ advisory: What we know so far
Japan experienced a series of powerful aftershocks, including a 5.7-magnitude quake off the east coast of Honshu and a 4.9-magnitude quake in Hokkaido, along with smaller tremors near southern Honshu, according to the European Mediterranean Seismological Centre.
The Japanese Fire and Disaster Management Agency has revised the casualty count from Monday night’s 7.5-magnitude earthquake, confirming that 51 people were injured across Hokkaido, Aomori and Iwate provinces. Seven of those were rated as suffering severe injuries.
In the aftermath of that powerful tremor, Japan’s weather agency issued its first-ever top-tier warning for a “megaquake”, or an earthquake of magnitude 8 or greater.
The megaquake advisory covers 182 municipalities across seven prefectures along the Pacific coast, from Hokkaido down to Chiba.
Officials have said that there has been no significant damage to major infrastructure and that nuclear power plant facilities were also unscathed after Monday’s earthquake.
Municipalities ramped up their preparedness in the wake of the megaquake advisory, which is in effect until 16 December. Local governments updated residents, checked emergency stocks, and tested communication systems.
Citizens were urged to keep grab-and-go emergency megaquake kits ready. Officials also issued public safety recommendations and urged families to sleep in the same room as elderly or vulnerable members and wear day clothes at night to allow faster evacuation in case of any emergency.
Most schools across northern Japan resumed classes today. Students shared stories of fear during the quake, but said daily life was slowly returning to normal. Drills and evacuation reviews took place in many classrooms, according to local reports.
Some examples of damage have been reported after Monday's quake, including to the historic Chojasan Shinra Shrine in Aomori's Hachinohe city. A pub owner in Hachinohe was seen taping bottles to the wall after the quake smashed untethered glass items.
In the wake of Monday’s 7.5-magnitude earthquake, social media saw a wave of fake videos and conspiracy theories about the quake’s cause. Officials urged the public to rely only on verified government sources.
Even though the megaquake advisory remains in place and citizens have been urged to stay vigilant, there is currently no need for citizens to evacuate.
Google blamed for ‘dangerous’ tsunami information after Monday’s earthquake
Google’s AI-generated tsunami summaries reportedly gave dangerously false information after Monday’s earthquake in northern Japan, incorrectly saying that all tsunami warnings had been lifted while alerts were still active.
Tests by The Asahi Shimbun showed that the AI repeatedly provided outdated and inaccurate details, including wrong earthquake data.
Experts warned that such AI “hallucinations” pose serious risks during disasters, where lives depend on accurate, real-time information.
Masahiro Tsuji, a senior consultant at Faber Company Inc who specialises in the mechanics of search engines, told the outlet that using AI-powered answers during emergencies is very dangerous.
“AI-generated search results may present misinformation that appears credible, a phenomenon known as ‘hallucination,’” he said.
“False information must not be displayed--even once--in the field of disaster response, where lives are at stake,” Tsuji said.
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