A series of powerful earthquakes that hit western Japan have left at least 48 people dead and damaged thousands of buildings, vehicles and boats.

A 7.6-magnitude earthquake in Japan has killed at least six, knocked out power for tens of thousands of homes in the region and forced many to evacuate from coastal areas.

Japanese officials argue the water from the tsunami-wrecked Fukushima nuclear plant will be treated to legally releasable levels and further diluted with large amounts of seawater.

Emperor Naruhito and Prime Minister Yoshihide Suga were slated to mourn the dead at a commemorative anniversary ceremony in Tokyo.

A typhoon slammed into northern Japan on Tuesday evening, threatening to bring floods to an area still recovering from the 2011 tsunami.

A Japanese seaside town, known to be popular with tourists, has decided to raise awareness about the dangers of tsunamis by posting a computer graphics simulation of a seismic sea wave striking the ancient municipality.

Five years after a tsunami damaged the Fukushima nuclear power plant in Japan, wild boars are wreaking havoc in nearby towns.

It has been five years since a magnitude-9.0 earthquake rattled northeastern Japan, claiming at least 15,000 lives and leaving more than half a million people homeless.

Japan is looking to fend off future disasters by building a nearly 400-kilometre chain of cement sea walls, at places nearly five stories high.

The $200,000 device is called a seismometer, and measures movement in the ground, including seismic waves.