DRAMA around Kim Jong-un's nuclear program has added credibility to threats his next test could be over the Pacific.

And this has dire implications for the future of Kim Jong-un's nuclear testing program.

The granite mound is crumbling under its own weight, making it useless for further nuclear tests.

Executive Secretary of the Comprehensive Nuclear-Test-Ban treaty Organisation Lassina Zerbo earlier this month said sensors had detected two small earthquakes under Mount Mantap on October 12. These were similar to two others detected since September 3, shortly after North Korea exploded its largest weapon yet - what it claimed to be a miniaturised thermonuclear warhead.

These earthquakes are believed to be the mountain falling in on cavities left behind when nuclear devices were exploded, leaving enormous caverns of vaporised rock. This has previously raised fears radioactive dust and gas from the Punggye-ri test site could be released into the atmosphere.

But Kim Jong-un has continued to assert his desire to refine his nuclear weapons arsenal to counter that of the United States.

"Before we can engage in diplomacy with the Trump administration, we want to send a clear message that the DPRK has a reliable defensive and offensive capability to counter any aggression from the United States," a North Korean official reportedly said overnight, adding that an above-ground nuclear detonation would be part of that "message".


Federation of American Scientists for nuclear and defence policy senior fellow Adam Mount says the precarious state of the Punggye-ri test site makes this a disturbingly real proposition.

Dr Mount said an above-ground detonation was not necessary to establish a credible nuclear deterrent, pointing out India and Pakistan as having both limited their tests to underground.

North Korea's six nuclear tests to date have all been underground, the most recent earlier this month by far its largest.

"No-one doubts that DPRK can create a nuclear yield, and a warhead does not need to see the sky to test miniaturisation, staging, etc," Dr Mount wrote. "So while an above-ground test might be useful, it is not strictly required to achieve a credible deterrent."

But miniaturisation of a thermonuclear warhead to the point it was small enough and light enough to be carried by an intercontinental ballistic missile (ICBM) will require further development - and testing.

"DPRK may be considering an atmospheric test due to instability in Mount Mantap," Dr Mount said.

He says the four "seismic events" at the Punggye-ri test site since September have been backed up by satellite photograph observations of debris and land slides.

"(The) tunnels may not be stable," he says, making the test site unusable.

And Kim Jong-un, his nuclear test options now limited, may see the propaganda value of pictures of a mushroom cloud to outweigh the risk of contamination, and international condemnation.

"It is possible DPRK wants to release video of a miniaturised warhead detonating to remove any semblance of doubt," Dr Mount adds.


North Korean Foreign Minister Ri Yong Ho warned the United Nations last month that Kim Jong-un was deliberating detonating "an unprecedented scale hydrogen bomb" over the Pacific. This was in response to comments from President Trump that he would "totally destroy" North Korea.

The last time an atmospheric nuclear weapon test was conducted was when China detonated a device in 1980.

And Kim Jong-un may be in a foul enough mood to do it.

Yesterday, North Korea expressed anger at a United States / South Korean plan to "decapitate" its leadership. Details of the Special Forces assassination squads were reportedly among many gigabytes worth of data "hacked" from South Korean military servers late last year.

And a new bout of military exercises between Seoul and Washington has again raised Pyonyang's ire.

The North's foreign ministry has accused the United States of provoking the country by mobilising the aircraft carrier and other war assets near the peninsula. "Such military acts compel (North Korea) to take military counteraction," said Kim Kwang Hak, a researcher at the Institute for American Studies at the ministry. "We have already warned several times that we will take counteractions for self-defence, including a salvo of missiles into waters near the US territory of Guam."

In August, North Korea issued a similar threat, saying its military had presented Kim Jong Un with plans to launch intermediate-range missiles to create "enveloping fire" near Guam, a key US military hub in the Pacific.

Japan's Chief Cabinet Secretary Yoshihide Suga in September called Pyongyang's remarks and behaviour "completely unacceptable".

He said a test over the ocean needed to be high in the atmosphere to limit radioactive fallout. But risks included damage from an electromagnetic pulse (EMP) - a flash of energy which can destroy electronics and power grids.

Pyongyang has in the past threatened to mount just such an EMP attack on the United States or its allies.

"If it doesn't go exactly as planned and the detonation occurs at a lower altitude we could see some EMP-like effects for anything in the area," he said. "A lot of dead fish too."


Deputy UN Ambassador Kim In Ryong has told the General Assembly's committee on disarmament that the situation on the Korean peninsula "has reached the touch-and-go point and a nuclear war may break out any moment."

"Unless the hostile policy and the nuclear threat of the US is thoroughly eradicated, we will never put our nuclear weapons and ballistic rockets on the negotiation table under any circumstance," he said.

Following a series of missile launches and a sixth nuclear test, Kim said his country "had passed the final gate" toward becoming a full-fledged nuclear power, with the means to deliver a nuclear strike.

"The entire US mainland is within our firing range and if the US dares to invade our sacred territory, even an inch, it will not escape our severe punishment in any part of the globe," said the North Korean diplomat.

But US Secretary of State Rex Tillerson said Sunday that Trump wanted to avoid war, even though the president said on Twitter that Tillerson was "wasting his time" with diplomacy.

"He's not seeking to go to war," Tillerson said, adding that efforts would "continue until the first bomb drops."