Japan has lifted its warning regarding an elevated risk of a significant earthquake, one week after a strong tremor near the Nankai Trough seabed prompted the government to issue its first “mega-earthquake” advisory. Citizens can now return to their normal routines, as no abnormalities in seismic activity have been observed in the past week at the Nankai Trough, which lies along Japan’s Pacific coast, said Yoshifumi Matsumura, the Minister for Disaster Management, on Thursday.
On August 8, the Japan Meteorological Agency (JMA) issued a warning that there was a “relatively high chance” of a Nankai Trough “mega-earthquake” with a magnitude of up to 9, following a magnitude 7.1 earthquake that struck the southwestern part of the country. Although the warning was not a definitive prediction, the government urged residents in western and central regions to review evacuation procedures in case of a major earthquake and tsunami.
Prime Minister Fumio Kishida canceled a planned trip to Central Asia and Mongolia over the weekend to prioritize disaster management efforts. The warning that such a disaster could affect the island nation of 125 million people led thousands of Japanese to cancel their vacation plans and stockpile supplies, resulting in empty shelves at some stores.
Matsumura cautioned that lifting the warning did not mean the risk of a major earthquake had been eliminated. The recent 7.1 magnitude earthquake that hit Kyushu resulted in 15 injuries and triggered a tsunami warning. The government has previously stated that there is about a 70 percent probability that the next “mega-earthquake” will strike within the next 30 years.
The Nankai Trough is an 800 km long underwater trench located between two tectonic plates in the Pacific Ocean, running parallel to Japan’s Pacific coast, including the Tokyo region, which is home to approximately 40 million people. Japan is situated on top of four major tectonic plates and is one of the most earthquake-prone countries in the world, experiencing around 1,500 tremors each year, most of which are minor.
In 1707, all segments of the Nankai Trough ruptured simultaneously, triggering an earthquake that is still considered the second most powerful in the country’s history. This earthquake also preceded the latest eruption from Mount Fuji and was followed by two significant Nankai megathrust earthquakes in 1854, as well as one each in 1944 and 1946.
More than 15,000 people lost their lives during a magnitude 9 earthquake in 2011 and the tsunami it triggered. The waves also led to the meltdown of three reactors at a nuclear power plant in northeastern Japan.