Tremors were felt in Tokyo and along the Japanese east coast, but there were no tsunami warnings.
The quake was strong, but deep, and was centered offshore near Torishima, part of the Izu Islands at about 600 kilometers (370 miles) below the earth's surface.
The U.S. Geological Survey measured the quake at 6.5-magnitude and said it was 404 kilometers (251 miles) deep.
Normally a quake of this magnitude is capable of causing major damage to buildings. However, Japanese buildings are built with earthquakes in mind and could withstand the shaking.
National broadcaster NHK did say that some train lines stopped briefly for safety checks, but merely as a precaution.
