North Korea was struck by strong tremors on Sunday, with the South’s officials saying it could be due to a nuclear test.

The USGS initially reported the first tremor as a 5.6 magnitude, but later raised it to 6.3, while China’s earthquake administration said it detected a 6.3 magnitude earthquake in Northeastern North Korea, calling it a “suspected explosion,” Reuters reported.

The depth of the first quake was recorded as zero kilometers, the China earthquake administration said, according to Reuters.

The report cited the USGS as saying the first tremor occurred at around 12 noon North Korea time.

China’s earthquake administration later said it detected a second quake of magnitude 4.6 at a depth of zero kilometers, which it called a “collapse,” Reuters reported, noting the second tremor came eight minutes after the first at nearly identical coordinates.

A South Korean military official told NBC News that the first quake was artificial, while Yonhap reported the military said the first tremor was located near the North’s nuclear test site.

South Korea’s Blue House, the country’s equivalent of the White House, said that the North may conducted another nuclear test, its sixth, the South’s official news agency Yonhap reported.

The South’s President Moon Jae-in has called a National Security Council meeting, while the country’s military raised its alert level, Yonhap reported.

Previous tremors in the reclusive country have been caused by nuclear tests. The wave form signal for an explosion and an earthquake are different, allowing geologists to distinguish a man-made tremor.

The potential nuclear test followed North Korea saying on Sunday that it had developed a more advanced thermonuclear weapon of “great destructive power,” which it would load onto an intercontinental ballistic missile, Reuters reported.

Dr. Koh Yu Hwan, a professor of North Korea studies at Dongguk University in Seoul told NBC News on Sunday that given the North’s statement on a hydrogen bomb earlier in the day, the test would likely have involved such a bomb.

That would mean the North had nearly completed its efforts to become a legitimate nuclear power, he said.

“We passed the point of trying to resolve North Korean nuclear problem through dialogue,” Koh said. “It would be difficult not to give recognition as a nuclear state in order to resolve the nuclear issue now and, certainly, it would be hard to make any progress by asking North Korea to abandon its nuclear ambition at this late stage.”

Source: cnbc china
North Korea shaken by strong tremors, with South's officials saying it may be nuclear test