A strong earthquake hit southern Japan on Thursday, resulting in mainly minor injuries but increasing worries about potential significant seismic activity from an undersea trough located east of the coast.
Seismologists convened for an emergency meeting following the quake, raising concerns about future large earthquakes related to the Nankai Trough, known for causing devastating quakes in the past. They indicated that the likelihood of a future quake affecting the area from Kyushu to central Japan now appears higher than previously assessed.
The Japan Meteorological Agency (JMA) emphasized its commitment to monitoring tectonic plate movements around the Nankai Trough closely.
While there is no immediate threat of a major quake, experts have advised coastal residents along the 500-kilometer (310 miles) trough to review their earthquake preparedness plans. University of Tokyo seismologist Naoshi Hirata, part of the expert panel, communicated this during a joint news conference with JMA officials. He indicated that there is a 70-80% likelihood of an 8 or 9 magnitude earthquake occurring from the Nankai Trough within the next 30 years, noting that the recent quake has increased this probability, although specific timing and location remain uncertain. He urged residents to maintain heightened alertness for at least a week.
The earthquake registered a magnitude of 7.1 and was centered in the waters off the eastern coast of Kyushu, approximately 30 kilometers (about 19 miles) beneath the sea surface, as reported by the JMA. The city of Nichinan and surrounding areas in Miyazaki prefecture on Kyushu island experienced the most intense shaking.
Tsunami waves reaching up to 50 centimeters (1.6 feet) were recorded along parts of Kyushu’s southern coast and the nearby island of Shikoku about half an hour post-quake. Tsunami warnings were issued but were lifted for most areas after three hours and for all coastlines within five and a half hours.
In total, nine individuals sustained minor injuries on Kyushu, with no significant damage reported.
Prime Minister Fumio Kishida stated that the government’s crisis management team would enhance disaster preparedness efforts and urged residents to remain vigilant and rely on official information, cautioning against the spread of misinformation.
The United States Geological Survey assigned a yellow alert for estimated economic impacts due to the earthquake, indicating that localized damage might occur. A green alert was given for fatalities, implying a low probability of casualties related to shaking.
JMA official Shigeki Aoki cautioned that strong aftershocks could be expected for about a week. NHK public television reported that windows at Miyazaki airport, close to the epicenter, had shattered, leading to a temporary closure of the runway for safety inspections.
Kyushu “shinkansen” super-express trains resumed regular service following safety checks, while several local train lines in affected areas would remain suspended until Friday, according to Kyushu Railway Co.
Images broadcasted by NHK showed groups of people gathering at designated evacuation sites on higher ground.
In Osaki, Kagoshima prefecture, some concrete walls collapsed and a wooden house was damaged, though no injuries were reported.
The Nuclear Regulation Authority confirmed that all 12 nuclear reactors, including three currently operational in Kyushu and Shikoku, were deemed safe.
Concerns over earthquakes in proximity to nuclear power plants have been heightened since the catastrophic earthquake and tsunami in March 2011, which led to the Fukushima disaster.
Japan is situated along the Pacific “Ring of Fire,” an area known for its seismic activity, making it one of the most earthquake-prone nations globally. An earthquake in Japan’s north-central region of Noto on January 1 resulted in more than 240 fatalities.