North Korea’s sixth nuclear test on Sunday may not have been a test of a hydrogen bomb as claimed, according to experts. Photo by KCNA/UPI | License Photo

Sept. 5 (UPI) -- North Korea's sixth nuclear test may have involved a bomb that released the same energy as 108 kilotons of TNT, according to a team of Chinese scientists.

But Japan's defense ministry said the bomb could have unleashed as much as 120 kilotons.


The wide-ranging estimates follow an assessment from the research group Norwegian Seismic Array that pointed out large test explosions could be accomplished in a number of ways, according to The New York Times.

A team of Chinese researchers at the University of Science and Technology of China in Hefei, Anhui province, said the most recent test took place Sunday at North Korea's Punggye-ri test site, and their data had a margin of error of no more than 100 meters.

The impact of the explosion risks "major environmental disaster," said Wang Naiyan, the former chairman of the China Nuclear Society.

Another test could cause the mountain at Punggye-ri to collapse, the South China Morning Post reported.

"We call it 'taking the roof off.' If the mountain collapses and the hole is exposed, it will let out many bad things," the scientist said.

It is unclear, however, whether the North Koreans built vertical or horizontal tunnels.

Vertical tunnels are more expensive but would mitigate damage, according to Wang.

"A 100-kiloton bomb is a relatively large bomb. The North Korean government should stop the tests as they pose a huge threat not only to North Korea but to other countries, especially China," Wang said.

In Tokyo on Tuesday, Japanese Defense Minister Itsunori Onodera said the bomb could have emitted as much energy as 120 kilotons of TNT, NHK reported.

The Japanese official also said the artificial quake resulting from the test measured 6.0 on the Richter scale.

Onodera did not rule out the possibility of a hydrogen bomb test, and said investigation is ongoing.

Nuclear experts said the explosion on Sunday was four to 16 times more powerful than Hiroshima, and North Korea may be in the process of developing a hydrogen bomb.