Major earthquake off Japan's north coast prompts tsunami alert

Tokyo — A powerful earthquake struck off the northern Japanese coast Monday, prompting the Japan Meteorological Agency (JMA) to issue a tsunami alert for a wide section of coastline, though waves of only about three feet were observed and the emergency appeared to be easing.

The U.S. Geological Survey reported the quake had a magnitude of 7.4. Earlier reports from the JMA ranged from 7.5 to 7.7. It occurred off the coast of Sanriku in northern Japan at around 4:53 p.m. (2:53 a.m. Eastern on Sunday), at a depth of about 6 miles below the sea surface, the agency said.

A tsunami wave of about 2.6 feet was detected at the Kuji port in the Iwate prefecture within one hour of the quake, and a smaller tsunami wave of 1.3 feet was recorded at another port in the prefecture, the agency said.

The tsunami alert put in place earlier for waves as high as 10 feet was later lowered to an advisory, and the U.S. Pacific Tsunami Warning Center said the tsunami threat from the quake had passed.

The JMA urged residents in the region to stay away from the coast or along rivers and take shelter on higher ground. Iwate and three other northern prefectures issued non-binding evacuation advisories to more than 128,000 residents, according to the disaster management agency.

The Fire and Disaster Management Agency said officials were assessing the situation but so far no damage or injuries had been reported, including at power stations and other facilities. The Nuclear Regulation Authority said nuclear power plants and related facilities in the region were all intact and no abnormalities were detected.

Prime Minister Sanae Takaichi told reporters in Tokyo that the government had established an emergency task force, and television screens flashed warnings for people in Iwate, Aomori and Hokkaido prefectures to evacuate. 

Japan's government warns small chance temblor could trigger mega-quake

The government later issued an advisory for northern coastal areas of an increased risk of a possible mega-quake induced by the Monday temblor. The Cabinet Office and the JMA said there was a 1% chance of a mega-quake occurring on the northern Japanese coast in the next week or so following the powerful quake earlier in the day.

Officials said the advisory is not a quake prediction but urged residents to raise their preparedness, such as emergency food and their grab bag just in case, 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.

15 years since Fukushima earthquake and tsunami disaster

It has been 15 years since a magnitude 9.0 earthquake struck, unleashing a massive tsunami on March 11, 2011, ravaging parts of northern Japan. More than 22,000 people were killed and nearly half a million people were forced to flee their homes, most of them due to tsunami damage.

Some 160,000 people fled their homes in the Fukushima Prefecture 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.

There were initial reports in Japanese media that at least two nuclear power plants in the northeast region under a tsunami warning on Monday were thus far unaffected by the earthquake. Both of the plants are currently offline.

It was the tsunami that came after the 2011 temblor that caused most of the damage at the Fukushima Daiichi plant, however.