A rare magnitude 5.8 earthquake has struck off North Korea in the Sea of Japan, but was unlikely to cause any damage, the US Geological Survey says.
An earthquake of that size is unusual for that area but not unprecedented, USGS seismologist Julie Dutton told Reuters following Thursday's quake. She said the last large quake in that part of the Sea of Japan was in 1994.
North Korea causes seismic events when it conducts underground nuclear bomb tests, but Dutton said there was nothing to indicate this quake was a man-made event. All of North Korea's underground nuclear tests have been conducted on land.
Major Jamie Davis, a Pentagon spokesman, said initial indications showed that the earthquake was not caused by a North Korean nuclear test because of the location and depth of the quake.
Davis added that the Pentagon would continue to study the seismic activity.
The quake, which struck early in the morning on Thursday, was very deep, 538km below the seabed, and unlikely to cause any damage. Its epicentre was 180km southeast of the North Korean city of Chongjin.
It was initially reported as a magnitude 6.0 but was later revised to 5.8.
