An earthquake with a preliminary magnitude 6.5 struck northeastern Japan late Wednesday, the U.S. Geological Survey said, shaking buildings in the Tokyo region and briefly shutting down train lines. There was no danger of a tsunami but two people were reportedly injured.
The quake hit at 8:44 p.m. (1144 GMT) Wednesday 48 kilometers (30 miles) below the sea off the coast of Ibaraki prefecture, about 120 kilometers (70 miles) northeast of Tokyo. Japan's Meteorological Agency measured the quake's magnitude at 6.3, but the USGS put it at 6.5.
The region should brace for aftershocks measuring at least magnitude 5.0 over the next few days, ministry spokesman Takeshi Hachimine said in a news conference following the quake.
A woman in Ibaraki cut her nose after falling out of her bed, Kyodo News agency reported, while another was injured in Chiba, outside Tokyo. Police spokesman Meihan Toyoshima could not confirm the reports, saying there had been no reports of injuries so far.
A nuclear power plant in Tokaimura near the quake zone shut down automatically, but there were no reports of damage, Toyoshima said. Electricity to about 600 homes in Ibaraki was cut off following the quake but was restored in less than a minute, according to Tokyo Electric Power Company spokesman Kiyoto Ishikawa.
Officials at Tokyo's Narita international airport said its runways were closed after the quake but reopened in about 10 minutes. A major expressway outside Tokyo, also sealed off for inspection, reopened shortly, the Road Traffic Information Center said.
High-speed train services north of Tokyo were suspended but quickly resumed, Kyodo said. Japan Rail train services in the capital were functioning normally, according to the rail company's information hot line.
It was the second jolt in the area in recent days. A 5.1 quake outside Tokyo on Sunday shook the capital region and injured two people, though it caused no serious damage.
Japan, one of the world's most earthquake-prone countries, sits atop four tectonic plates. The last major earthquake to hit Tokyo killed some 142,000 people in 1923, and experts say the capital has a 90 percent chance of suffering a major quake in the next 50 years.
The metropolitan region is home to 35 million residents, and the government estimated earlier this year that 11,000 people would die and Japan would suffer about 112 trillion yen (US$1 trillion; Ђ840 billion) in economic damage if a 7.3 magnitude quake were to strike the capital, according to the AP.
Last October a 6.8-magnitude earthquake hit northern Japan, killing 40 people and damaging more than 6,000 homes. It was the deadliest to hit Japan since 1995, when a magnitude-7.2 quake killed 6,433 people in the western city of Kobe.
Powerful quakes in 1703, 1782, 1812 and 1855 also caused vast damage in the capital.