On Tuesday, August 13, Japan's Meteorological Agency (JMA) maintained its "mega-earthquake" advisory warning, raising questions about the predictability of earthquakes and causing widespread anxiety throughout the archipelago. Some are stocking up on essentials. Others are canceling their trips to the affected areas. The apprehension is exacerbated by Prime Minister Fumio Kishida's decision to cancel a trip to Central Asia in order to "assume [his] responsibility for crisis management."

The alert was issued for one week following the magnitude 7.1 earthquake in Miyazaki prefecture (southwest) on August 8. The disaster resulted in 14 injuries and some material damage, but the epicenter was located in the Nankai Trough. The JMA fears that a mega-earthquake of a magnitude greater than 8 could occur in this fault zone, where the Philippine plate plunges beneath the Eurasian plate and stretches for almost 700 kilometers from Suruga Bay (central Japan) to eastern Kyushu (south-west Japan). A total of 707 municipalities are under warning.

Since then, the Japanese have multiplied their precautionary purchases, causing shortages. Popular products on e-commerce sites like Rakuten include portable toilets, canned goods, rice and water. Additionally, stores in Tokyo are restricting water purchases to one pack per person.

The alert affects the tourism sector as Japan enters the traditional "Bon" vacation week − a period of Buddhist celebration of ancestors − punctuated by numerous festivals.

Holiday resorts suffer travel cancellations and some cities are cancelling events. This was the case for the fireworks display scheduled for August 10 on Shirarahama beach (central Japan). Beach access has even been closed to swimmers, such as at Hiratsuka beach in Kanagawa prefecture, south of Tokyo, and Aoshima beach in Miyazaki.

The alert led to a surge of false information on social media. Messages initially claimed the mega-earthquake would occur on August 10, then the date changed to August 11, and now it's said to happen on August 14. Some even interpreted the shape of the clouds as a sign of the impending disaster.

"After a major tremor, 'earthquake cloud' claims and conspiracy theories about artificially induced earthquakes abound. People need to take a deep breath and avoid spreading such hoaxes," reminded Kentaro Araki, a researcher at JMA.

According to scientists, powerful earthquakes on the Nankai fault occur on average every 100 to 150 years. Considered one of the most powerful ever recorded in the archipelago, the 1707 earthquake was responsible for Mount Fuji's most recent eruption. The most recent, of magnitude 7.1 and 8, date from 1944 and 1946.

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