A strong earthquake with a magnitude of 5.9 jolted northern Japan yesterday in the latest aftershock to hit a region struck by a deadly tremor last month, scaring thousands still seeking refuge in makeshift shelters.
The earthquake struck at 11:15 a.m. (0215 GMT) and its focus was near those of the other quakes that have hit the Niigata region, the Meteorological Agency said. A series of smaller quakes followed. No tsunami warning was issued.
Kyodo news agency said 10 people were injured including a 68-year-old construction worker who was taken to hospital after being buried in a landslide and six people who were hurt slightly by parts of a wall that collapsed.
High-speed bullet trains in the area were temporarily halted and parts of local highways closed for safety checks, broadcaster NHK said.
The Niigata region, 250 kilometres north of Tokyo, was hit by a 6.8 magnitude earthquake on October 23 that killed at least 39 people. That was Japan's deadliest quake since one with a magnitude of 7.2 killed more than 6,400 in Kobe in 1995.
The latest aftershock frightened local residents, around 19,000 of whom are still seeking refuge in places such as public buildings, tents or cars after last month's earthquake.
"It's scary. They keep coming, so you can't relax," one woman told NHK following the aftershock.
The Meteorological Agency has warned residents not to go close to buildings damaged by the quakes as the slightest aftershock may trigger a collapse.
After yesterday's tremor, the agency said there was a roughly 40 per cent chance that another aftershock of magnitude 5.0 or larger could hit the same region within three days.
The magnitude is measured by a technique similar to the Richter scale but adjusted for Japan's geological characteristics.
Seismologists have said the initial quake occurred in a "seismic gap" - part of an active fault that had experienced little or no seismic activity for a long period, causing stress to build up and making an earthquake more likely.
They have said there were still areas in the fault where the stress remained to be released, meaning aftershocks could occur in such places.
Earthquakes are common in Japan, one of the world's most seismically active areas. It accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.