2 weeks ago
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Japan has issued a megaquake advisory after a magnitude 7.5 earthquake struck off the eastern coast of Aomori, the northernmost prefecture of Japan’s main island of Honshu.
Damage from the quake was modest – 34 mostly mild injuries and some damage to roads and buildings.
Officials said the advisory announced on Tuesday was not a prediction and the probability of a magnitude 8 or larger quake was only about 1%. But they hope the advisory will make sure the public is prepared in the event of a powerful quake that could have the devastation of the 2011 disaster that killed nearly 20,000 people.
Officials said there was an increased risk of a magnitude-8 or larger quake within the next week and urged residents, especially along coastal areas, to be prepared.
The southern half of Japan’s Pacific coastline received a “Nankai Trough” megaquake advisory in the summer of 2024, but the ambiguity of that warning led to panic buying of emergency food, event cancellations and business closures.
The Japan Meteorological Agency said Monday’s powerful quake temporarily increased potential risks in the regions of Hokkaido and the Sanriku coast. That is where the Pacific plate beneath Japan forms the two trenches – the Japan trench and Chishima trench – that have caused many large quakes in the past.
Experts say the deadly quake and tsunami in 2011 was caused by movement associated with the Japan trench. It spans from off the eastern coast of Chiba to Aomori, and the Chishima trench goes from the eastern coast of Hokkaido to the northern islands and the Kurils.
In explaining the advisory, the JMA said the magnitude 9.0 quake in 2011 occurred two days after a magnitude 7.3 temblor that struck in the Japan Trench off the eastern coast of Iwate, one of the hardest-hit areas in that disaster as well as in Monday’s quake.
The 2011 quake caused a tsunami that battered northern coastal towns in Iwate, Miyagi and Fukushima prefectures. The tsunami, which topped 15 metres (50 feet) in some areas, damaged the Fukushima Daiichi nuclear power plant.
Another offshore megaquake in the Hokkaido-Sanriku area could cause up to a 30-metre (98-foot) tsunami in the region, kill as many as 199,000 people, destroy up to 220,000 houses and buildings, and cause estimated economic damages of up to 31 trillion yen ($198bn), according to a government estimate.
The areas covered by the advisory extend across 182 municipalities from Hokkaido to Chiba prefecture.
Officials are stressing the latest advisory has no prediction for any megaquake happening at any specific time or location.
Residents have been urged to be cautious and prepared while continuing their daily activity and work. Officials advised people to keep an emergency bag containing a few days’ worth of daily necessities along with shoes and helmets. People in the region are also advised to discuss evacuation procedures with family members and sleep in day clothes, not in pyjamas, so they can flee immediately. Furniture should also be fixed to the floor or the wall.
Iwaki city in Fukushima urged residents to register for emergency emails, while officials in the town of Oarai in Ibaraki prefecture, north-east of Tokyo, inspected wireless communication devices.
Japan’s megaquake advisory last year contained a lot of scientific jargon, worrying and baffling many across the country. Some towns closed beaches and cancelled annual events, disappointing many travellers during Japan’s Buddhist holidays.
Many people postponed planned trips and rushed to stock up on rice, dried noodles, bottled water and portable toilets, leaving shelves empty at many supermarkets in western Japan and even Tokyo, which is outside the at-risk area.
