Hours after the quake, the Japan Meteorological Agency (JMA) issued a special advisory warning of a slightly elevated risk of a temblor with a magnitude of 8 or stronger in the coming days.

There was a 1 per cent chance of a megaquake, compared to 0.1 per cent at other times, it said, particularly close to the Chishima Trench, about 150km (93 miles) off the coast of Hokkaido, and the Japan Trench, which is further south and around 300km offshore.

However, the warning was only of increased risk, rather than a specific prediction, it said.

“Although the probability is low, there is a possibility of another major earthquake occurring,” the JMA said in a statement. “Therefore, please review your earthquake preparedness measures in these areas.”