A magnitude 7.1 earthquake struck off the coast of Miyazaki Prefecture on Thursday, prompting a tsunami advisory for parts of the coast of Kyushu and Shikoku and for the Meteorological Agency to issue an alert warning of a further possible megaquake along the Nankai Trough area, off the east coast of Japan, for the first time.
Thursday’s earthquake registered a lower 6 on the seven-point Japanese seismic intensity scale, occurring at 4:43 p.m. at a depth of 30 kilometers, with its epicenter in the Hyuganada sea off the coast of Miyazaki Prefecture.
A total of nine people were reported to have been injured in Kyushu’s Miyazaki and Kagoshima prefectures as of 7:30 p.m., according to the Fire and Disaster Management Agency. Among those, seven suffered minor injuries while the extent of injuries for the other two remain unclear.
Speaking at an emergency news conference, Chief Cabinet Secretary Yoshimasa Hayashi said a landslide had been reported in the city of Shibushi in Kagoshima Prefecture.
At its own news conference following the quake, the Meteorological Agency cautioned that people in the affected areas should be on alert for earthquakes measuring up to lower 6 for the next week, especially over the next two or three days. In areas where tremors were strongly felt, the risk of buildings collapsing and of landslides had increased, the agency added, warning people to stay vigilant surrounding quake activity and rainfall.
Tsunami waves of up to 1 meter were initially anticipated along coastlines in Ehime, Kochi, Oita, and Kagoshima prefectures in addition to Miyazaki, with the agency warning people to stay away from the sea and waterways until those advisories were lifted as tsunami waves can arrive repeatedly.
Small waves were recorded in some areas. A 50-centimeter tsunami was recorded at Miyazaki Port at 5:14 p.m., a 40-cm wave reached Aburatsu Port on the Nichinan coast in Miyazaki at 5:23 p.m., and a 30-cm wave reached Tosashimizu in Kochi at 5:46 p.m. Tsunami advisories were lifted for areas outside of Miyazaki Prefecture at about 7 p.m.
After the earthquake, Prime Minister Fumio Kishida instructed authorities to share accurate information about the tsunami warning and any damage, urging residents to take necessary precautions to find shelter.
The government set up a task force under the helm of disaster management minister Yoshifumi Matsumura, Kishida told reporters Thursday evening.
Kyushu Electric Power said there was no impact from the earthquake on its Sendai and Genkai nuclear plants, which are located in the city of Satsumasendai in Kagoshima Prefecture and the Higashimatsuura district in Saga Prefecture, respectively.
Shikoku Electric Power said no shaking was detected at its Ikata Nuclear Power Plant in Ehime Prefecture — the only nuclear plant on Shikoku Island — adding that the plant’s Unit 3 has been shut down for routine inspections.
Several domestic flights scheduled to depart Miyazaki Airport after 5:30 p.m. were canceled. “The shaking was quite intense and lasted around 30 seconds,” a clerk at the airport told NHK. “We were told that some windows have shattered.”
As of shortly before 8 p.m., several local train lines across Kyushu were still suspended because of the earthquake.
JR Kyushu reported suspension of some train services on the Nippo Line, the Miyazaki-Airport Line, the Nichinan Line, the Hisatsu Line and the Kitto Line as well as delays elsewhere on those lines. It also noted ongoing delays on the Kagoshima Line and the Kyushu Shinkansen. The Kyushu Shinkansen and Minami Kyushu Shinkansen lines had resumed operations following the earthquake at around 5:25 p.m., media reported.
The Meteorological Agency’s alert warning about a possible large earthquake around the seismically significant Nankai Trough area, issued later Thursday, was its first ever. It is believed that the chance of a major earthquake occurring in the Nankai Trough is relatively higher than usual, according to the agency.
“I urge everyone to check information from the government, go back to basic disaster preparedness and get ready to evacuate immediately in the event of an earthquake,” Kishida said in reference to the risk of a Nankai Trough earthquake, urging people to refrain from spreading misinformation.
Large-scale quakes in the Nankai Trough have historically caused severe damage, originating from the plate boundary region stretching from Suruga Bay to offshore Hyuganada, according to the Cabinet Office. Such earthquakes have typically occurred in cycles of 100 to 150 years.
According to a 2022 evaluation by the Headquarters for Earthquake Research Promotion, there is a 70% to 80% probability of a magnitude 8 to 9 class earthquake occurring within the next 30 years.
On Friday, Kishida is scheduled to fly to Nagasaki to attend a ceremony to commemorate the 79th anniversary of the atomic bombing, and from there to head directly to Kazakhstan for a four-day tour of Central Asia. Kishida said he will decide whether to cancel these engagements or take further measures according to the developments of the next few hours.
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