The tremor was recorded at 10:18 am (0118 GMT) in Shimane prefecture at a shallow depth, the Japan Meteorological Agency (JMA) said.

The US Geological Survey recorded a slightly lower 5.8 magnitude reading which it then lowered to 5.7.

The quake measured upper-five on Japan's Shindo scale of shakiness in the western city of Yasugi.

At that level, heavy furniture may fall and drivers can have trouble steering.

The JMA said that the same region was hit soon afterwards by smaller quakes with magnitudes of 4.5, 5.1, 3.8 and 5.4, also with no tsunami alerts.

No abnormalities were detected at the Shimane nuclear plant as of 10:45 am, broadcaster NHK said, citing utility company Chugoku Electric.

Parts of the Shinkansen bullet train network were suspended due to a power blackout, operator JR West said. It was unclear if this was related to the quakes.

The military said it was conducting an aerial damage assessment and had established a disaster response liaison office.

"The government is collecting information on damage... People in the regions that were hit by strong shakes please continue to be careful about more quakes of the same strength," Prime Minister Sanae Takaichi said.

- Haunting memory -

Japan sits on top of four major tectonic plates along the western edge of the Pacific "Ring of Fire" and is one of the world's most seismically active countries.

The archipelago, home to around 125 million people, experiences around 1,500 jolts every year.

The vast majority are mild, although the damage they cause varies according to their location and depth.

Japan is haunted by the memory of a massive 9.0-magnitude undersea quake in 2011, which triggered a tsunami that killed around 18,500 people.

In 2024, the JMA issued its first special advisory of a possible "megaquake" along the Nankai Trough.

This 800-kilometre undersea trench is where the Philippine Sea oceanic tectonic plate is "subducting" -- or slowly slipping -- underneath the continental plate that Japan sits atop.

The government has said a quake in the Nankai Trough and subsequent tsunami could kill as many as 298,000 people and cause up to $2 trillion in damages.

The JMA lifted the 2024 advisory after a week but it led to panic-buying of staples like rice and prompted holidaymakers to cancel hotel reservations.

It issued a week-long second "megaquake" advisory in December 2025 after a magnitude-7.5 tremor struck off the northern coast.

The December 8 quake triggered tsunami waves of up to 70 centimetres (28 inches) and injured more than 40 people, but no major damage was reported.