Military spouse Kristen Lindholm and her kids experience the Tokyo Fire Department's earthquake simulator at Yokota Air Base, Japan, Oct. 16, 2024. (Akifumi Ishikawa/Stars and Stripes)
TOKYO — Japanese authorities are warning residents to remain alert for strong tremors in the coming days after a magnitude 6.6 earthquake struck southern Japan this week.
The earthquake occurred at 9:19 p.m. Monday in the Hyuganada Sea, approximately 12 ½ miles east-southeast of Miyazaki prefecture, according to the Japan Meteorological Agency.
The quake registered a maximum seismic intensity of lower 5 on Japan’s seismic scale in Miyazaki city and the towns of Takanabe and Shintomi, the agency said in a news release that night. Seismic intensities ranging from 1 to 4 were recorded across central to western Japan.
Officials cautioned that similar tremors could occur soon.
“Please be on the alert for earthquakes with maximum seismic intensity of lower 5 to occur in the next week or so, especially in the next two to three days,” the agency said.
The earthquake triggered aftershocks and a small tsunami, with waves of up to 8 inches observed in parts of Miyazaki and Kochi prefectures. Tsunami advisories were issued but later lifted.
Monday’s temblor came months after a magnitude 7.1 earthquake struck the Hyuganada Sea in August, prompting the agency to issue its first-ever megaquake advisory for the Nankai Trough. That advisory has since been withdrawn.
The Nankai Trough, a geological fault stretching from Suruga Bay near Shizuoka prefecture to the Hyuganada Sea, is a zone of significant seismic activity. The Philippine Sea Plate pushes beneath the Eurasian Plate at several centimeters per year, causing stress to accumulate until it releases in massive quakes, according to the agency.
Historically, the Nankai Trough experiences massive earthquakes every 100 to 150 years, with the last major event occurring approximately 80 years ago.
Following Monday’s earthquake, an expert panel was convened to assess the potential for another large quake. Later on Monday, the panel concluded that the likelihood of a megaquake along the trough remains unchanged.
“Even under normal circumstances, there is a 70% to 80% chance of a magnitude 8 to 9-class earthquake occurring along the Nankai Trough within the next 30 years,” the agency warned.
Authorities are urging residents to remain vigilant.
“It is important to keep in mind that an earthquake could occur at any time and to ensure that you are prepared on a daily basis,” the agency stated.
