The tremor followed a stronger quake of 8.5 magnitude on Saturday which had an epicentre off the Ogasawara islands, south of Tokyo, which caused no serious damage.
That quake was at a depth of 590 Km (370 miles).
The quake 398 Km (250 miles) south-east of the Izu Islands had a more shallow epicentre of 13.4 km (9.4 miles).