A RARE magnitude 5.8 earthquake struck off North Korea in the Sea of Japan on July 13, 2017.
The last large quake in that part of the Sea of Japan was in 1994.
An earthquake of that size is unusual for that area but not unprecedented.
North Korea causes seismic events when it conducts underground nuclear bomb tests, but 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. One in september 2016 produced a M5.3 earthquake recorded from seismic network across the world.
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. But 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.