A magnitude-6.8 earthquake first struck the southern coast of the island of Hokkaido, causing a small tsunami. The Meteorological Agency issued tsunami advisories along the northern coast, prompting some communities to issue evacuation advisories to residents near the coast.
A swelling of 20 centimeters (8 inches) was observed in the port of Hachinohe in Aomori about an hour later, with smaller changes reported elsewhere. The agency lifted all tsunami advisories within about 90 minutes.
About three hours later, a magnitude-6.1 quake shook buildings in the capital. It was centered just off the coast of Chiba, east of Tokyo, at a rather shallow 10 kilometers (6 miles) below the sea surface.
Narita International Airport briefly closed runways for inspection but later resumed operation. Several local train services were suspended for safety checks.
There were no abnormalities reported at nuclear power plants after the two earthquakes, operators said. Most of Japan's nuclear plants are offline for safety inspections.
This past Sunday, Japan marked the first anniversary of the massive magnitude-9.0 earthquake and tsunami that left some 19,000 people dead or missing, wreaked widespread damage along the northeastern coast, and triggered the worst nuclear accident since Chernobyl. Rebuilding has yet to fully begin in many coastal communities.
After the first quake on Wednesday, the town of Otsuchi in Iwate prefecture, where more than 800 died in last year's tsunami, issued an evacuation order to coastal households as a precaution, said prefectural disaster management official Shinichi Motoyama. No damage or injury was reported, he said.
Iwate was heavily damaged by last year's tsunami. Thousands of aftershocks have shaken the region since then, nearly all of them of minor or moderate strength.