Japan issues advisory for slightly increased risk of mega-quake in northern coastal areas

Japan issued an advisory on Monday for an increased risk of a possible mega-quake in northern coastal areas, induced by a major earthquake earlier in the day.

The Cabinet Office and the Japan Meteorological Agency said there is a one per cent chance for a mega-quake occurring on the northern Japanese coast in the next week or so following the powerful quake earlier Monday near the Chishima trough.

Officials said the advisory is not a quake prediction but urged residents to raise their preparedness, such as having emergency food and a go bag, while continuing their daily lives.

The advisory for the region is the second in recent months. One was issued following another major quake in December. No major subsequent quake occurred.

Earlier Monday, a magnitude 7.5 earthquake struck off the northeastern coast of Japan on Monday, as authorities urged residents to stay away from coastal areas where tsunami waves of up to three metres were expected.

The biggest waves were forecast to hit Iwate and Aomori prefectures at the top of Japan’s main Honshu island, and the northern island of Hokkaido, authorities said.

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There were no immediate reports of casualties or major damage, Japan’s ⁠top government spokesperson Minoru ⁠Kihara told a news conference as night fell ‌in the capital, Tokyo.

In the hour following the earthquake, which struck at 4:52 p.m. local time, tsunami waves as high as 80 centimetres had been detected, while warnings remained for waves as high as three metres. Japan’s Meteorological Agency (JMA) kept their tsunami alert in place while the Pacific Tsunami Warning Centre said the tsunami threat from the quake “has now passed.”

Several port towns including Otsuchi and Kamaishi — both hard-hit by a massive earthquake and tsunami in 2011 — issued evacuation orders for thousands of residents, according to public broadcaster NHK.

Prime Minister Sanae Takaichi said the government had set up an emergency task force and urged citizens in the affected areas to evacuate to safety.

Big aftershocks anticipated

Big aftershocks may occur in the following days and weeks, an official from JMA said at a separate televised press conference.

Ships sailed out of Hachinohe port in Hokkaido in anticipation of the waves, footage aired on NHK showed, as a “Tsunami! Evacuate!” alert flashed across the screen. A three-meter tsunami could cause damage to low-lying areas, flooding buildings, and anybody exposed would be caught in its currents, according to JMA.

Bullet train services in Aomori were halted due to the tremors, Kyodo news agency reported.

The quake measured an “upper 5” on Japan’s seismic intensity scale — strong enough to make it difficult for people to move around and cause unreinforced concrete-block walls to collapse. The tremor had an epicentre in the Pacific Ocean and was 10 kilometres deep, JMA said.

Located in the “Ring of Fire” of volcanoes and oceanic trenches partly encircling the Pacific Basin,  Japan is one of the world’s most earthquake-prone countries, with a tremor occurring at least every five minutes.

It accounts for about 20 per cent of the world’s earthquakes of magnitude 6.0 or more, such as the 2011 disaster that caused nuclear meltdowns at a Fukushima power plant.

Another 7.5 magnitude quake in December left dozens injured.

It’s been more than 15 years since a magnitude 9.0 earthquake and tsunami on March 11, 2011, ravaged parts of northern Japan, caused more than 22,000 deaths and forced nearly half a million people to flee their homes, most of them due to tsunami damage.

Some 160,000 people fled their homes in Fukushima because of the radiation spewed from the tsunami-hit Fukushima Daiichi nuclear power plant. About 26,000 of them haven’t returned because they resettled elsewhere, their hometowns remain off-limits or they have lingering concerns about radiation.