The plate boundary lies between Suruga Bay in central Japan, and the Hyogandana Sea in Kyushu to the south.
Previous earthquakes in the Nankai Basin have killed thousands. These large quakes occur every 90 to 200 years, the last being in 1946.
Experts say there is a 70% to 80% chance of a magnitude 8 or 9 earthquake occurring somewhere along the basin within the next 30 years, According to Kyodo News Agency, externalWorst-case estimates suggest that more than 200,000 people could die in the earthquake and possible subsequent tsunami.
But at a news conference on Thursday, Japan Meteorological Agency official Shinya Tsukada stressed that while “there is a relatively higher chance of another major earthquake compared to normal times,” they are not saying it will definitely happen “in a certain period of time.”
This current advisory — the least of two types of alerts available to administrators — will remain in effect for one week.
Authorities have asked residents to be on high alert in the coming days, and for those who cannot evacuate quickly to consider doing so voluntarily, according to NHK.
Officials also urged people to be cautious and continue their daily lives, checking evacuation routes when needed and making sure families have adequate supplies.
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