TOKYO – An earthquake with a preliminary magnitude of 6.6 struck southwestern Japan on Monday, with no immediate reports of injury or damage, and small tsunami observed in part of Miyazaki and Kochi prefectures, the weather agency said.
The Japan Meteorological Agency issued its second-ever Nankai Trough Extra Information, having first done so last August, and also opened an investigation as to whether there was an increased risk of a megaquake. The agency later concluded that the quake was not considered to have raised the risk.
The 9:19 p.m. quake measured a lower 5 on the Japanese seismic scale of 7 in Miyazaki, Shintomi and Takanabe in Miyazaki Prefecture, the agency said. The quake occurred in the Hyuga Nada Sea, off the coast of the prefecture, at a depth of approximately 36 kilometers.
(Source: Japan Meteorological Agency)
The magnitude was revised twice, initially estimated at 6.4, then updated to 6.9, and later adjusted to 6.6.
Tsunami with heights of around 20 centimeters were observed in part of Miyazaki Prefecture and 10 cm in some areas in Kochi Prefecture. The agency has since lifted all tsunami advisories.
Some sections in the Kyushu Shinkansen bullet train line were temporarily suspended due to the temblor, the train operator said.
No abnormalities were detected at the Ikata nuclear power plant in Ehime Prefecture and the Sendai nuclear power plant in Kagoshima Prefecture, according to the operators.
The quake was also felt in wide areas of western Japan.
The agency said that the temblor occurred at the western edge of the hypothesized epicenter of a Nankai Trough earthquake.
Megaquakes in the Nankai Trough that runs along the Pacific coast occur every 100 to 150 years, the last being the 1944 Tonankai and 1946 Nankai quakes that together struck a wide area from central to southwestern Japan.
A weather agency official speaks at a press conference in Tokyo on Jan. 13, 2025. (Kyodo)
A magnitude 8 to 9 earthquake has a 70 to 80 percent chance of occurring within 30 years, according to a government estimate.
The central government issued a Nankai Trough megaquake advisory on Aug. 8 following a M7.1 quake that occurred in the Hyuga Nada Sea, the first since the system’s implementation in 2017, and called for caution over the increased risk of strong shaking over a large area.
While the government urged increased disaster preparedness as opposed to evacuating in anticipation of a megaquake, some municipalities in the region set up evacuation centers and advised elderly residents, in particular, to secure themselves.
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