Two strong earthquakes within a minute of each other shook the Tokyo area and swayed office buildings Sunday morning.
There were no immediate reports of injuries.The first, more powerful earthquake at 11:09 a.m. registered 5.5 on the Richter scale, the Meteorological Agency said.
In Tokyo, the quake slightly rocked office buildings. In the city of Ito, on the Izu peninsula about 80 miles to the southwest, it knocked over parked motorcycles and threw canned goods from store shelves.
It was centered in the ocean off the peninsula about 60 miles southwest of Tokyo, officials said.
Trains on nearby land were delayed for about a half hour, a Japan Railways spokesman said.
The National Police Agency said it was still investigating damage.
At least 17,760 small quakes, 380 of them strong enough to be felt by residents, have shaken the Izu peninsula since Tuesday, the Meteorological Agency said.
The quakes have caused burst water pipes, gas lines leaks, and damage to roads and roofs.
The open-ended Richter scale measures the magnitude of a quake at its epicenter. An increase of one unit means a tenfold increase in ground motion.
A quake that measures 5 can cause considerable damage, and one that measures 6 can cause severe damage.