The quake, which the US Geological Survey measured at 6.0, struck at 9:26 p.m. (1226 GMT) in Kumamoto, central Kyushu at a relatively shallow depth of 10 kilometers (6.2 miles), the Japan Meteorological Agency said.
The quake was followed about 30 minutes later by another smaller one with a magnitude of 5.7, the agency said. That quake also did not generate a tsunami warning.
Japan's public broadcaster NHK reported that some buildings had collapsed on Kyushu with people possibly trapped, though details were scarce.
Cameras set up by NHK showed violent shaking at the time of the quake, which was felt throughout Kyushu.
Japanese media reported that shinkansen, or bullet, train service was halted on the island.
NHK showed some damage including broken concrete. Residents stood outside making calls on mobile phones.
Watermelons fell from store shelves and lay crushed on the floor of a supermarket in Kumamoto city, near the epicenter, NHK footage showed.
Objects fell from shelves and staff ducked under desks as the quake shook the NHK office in Kumamoto, video showed.
“We intend to do the utmost to grasp the situation," Prime Minister Shinzo Abe told reporters. "I’m now planning to hear what we have gathered on the situation."
Kyushu Electric Co. said it was checking conditions at its Genkai and Sendai nuclear plants.
An official at the Sendai nuclear plant in Kyushu, who declined to be named, said the plant was operating normally but that officials were checking for any abnormalities.
There were no irregularities at the Genkai or Sendai nuclear plants, which are on the southernmost main island of Kyushu, or at the Ikata plant on nearby Shikkoku, the Kyodo news agency reported.
Japan sits at the junction of four tectonic plates and experiences around 20 percent of the world's most powerful earthquakes.
But rigid building codes and strict enforcement mean even powerful tremors frequently do little damage.
A massive undersea quake that hit on March 11, 2011, sent a tsunami barrelling into Japan's northeast coast, leaving about 18,500 people dead or missing, and sending several reactors into meltdown at the Fukushima nuclear plant in the worst atomic accident in a generation.
source: interaksyon.com
