Last weekend, North Korea suspended its nuclear tests and shut down the site where the last six detonations took place: underneath Mount Mantap, in the country’s northeast.

The reasons are ostensibly diplomatic, pointing to a thaw in relations between Kim Jong-un’s regime and South Korea and the West, but some noted that Pyongyang might have also been worried that the mountain was at risk of collapsing, as it visibly shifted during the last nuclear test. However, two separate groups of Chinese scientists now say Mount Mantap did in fact collapse after that detonation.

That means there’s a risk of radioactive contamination spreading not only within North Korea, but to other countries in the region. The site is not far from North Korea’s borders with China and Russia.

According to geologists from the University of Science and Technology of China, the collapse took place minutes after Kim Jong-un’s regime conducted its last nuclear test in September of last year.

The test of the 100-kiloton bomb, which led Chinese seismologists to register a 6.3 magnitude earthquake, apparently opened up a hole of up to 656 feet in diameter. Part of the mountain then fell into the hole.

The findings of the team, led by renowned seismologist Wen Lianxing, are set to be published next month in the journal Geophysical Research Letters.

According to the Hong Kong-based South China Morning Post, another team from the China Earthquake Administration reckons the collapse created a “chimney” that could allow the escape of fallout. The publication quoted researcher Zhao Lianfeng from the Chinese Academy of Sciences as saying the site was “wrecked” beyond repair.

So Pyongyang’s renouncement of land-based nuclear tests, for now, appears to be motivated by more than mere diplomatic concerns. </s> BEIJING -- Research by Chinese geologists suggests that the mountain above North Korea's main nuclear test site has likely collapsed. That collapse has likely rendered the site unsafe for further testing and will require that it be monitored for any leaking radiation.

The findings by the scientists at the University of Science and Technology of China may shed new light on North Korean President Kim Jong Un's announcement that his country was ceasing its testing program ahead of planned summit meetings with South Korean President Moon Jae-in and U.S. President Donald Trump.

The results also support some of the findings of an earlier study by another group of Chinese researchers that was published last month by the journal Geophysical Research Letters.
• None Trump says N. Korea agreed to denuclearize, but that's not the case 



Nuclear explosions release enormous amounts of heat and energy, and the North's largest test in September was believed early on to have rendered the site in northeastern North Korea unstable.

Chinese authorities have said they've detected no radiation risk from samples collected along the border. Calls to those departments were not immediately answered on Thursday.

The data in the latest Chinese study was collected following the most powerful of North Korea's six nuclear device tests on Sept. 3, which is believed to have triggered four earthquakes over the following weeks. The yield of the bomb was estimated at more than 100 kilotons of TNT, at least 10 times stronger than anything the North had tested previously. (The bomb the United States dropped on Hiroshima in 1945 had a yield of about 15 kilotons.)

The University of Science and Technology of China paper, authored by Tian Dongdong, Yao Jiawen and Wen Lianxing, said the first of those earthquakes, which occurred 8 ½ minutes after the explosion, was "an onsite collapse toward the nuclear test center," while those that followed were an "earthquake swarm" in similar locations.

"In view of the research finding that the North Korea nuclear test site at Mantapsan has collapsed, it is necessary to continue to monitor any leakage of radioactive materials that may have been caused by the collapse," the authors said in a summary dated Monday and viewed Wednesday on the university's website.

The study is peer-reviewed and has been accepted for publication by the journal Geophysical Research Letters.

The Chinese study makes sense and is based on well understood research, said Rowena Lohman, a seismologist at Cornell University who wasn't part of the work. She said she believes there's an international effort that monitors these tests for radiation.

A study published last month by the journal, authored by a team led by Liu Junqing at the earthquake bureau in Jilin province along the border with North Korea, found similar results of the Sept. 3 explosion. It described the aftershock that followed seconds later as most likely a "rapid destruction of an explosion-generated cracked rock chimney due to cavity collapse."

North Korea's nuclear tests are of special concern to Beijing, since the test site near the town of Kilju is less than 60 miles from the border with China.

North Korean nuclear tests have caused seismic events in Chinese border towns and cities, forcing evacuations of schools and offices, sparking fears of wind-born radiation and leading to a backlash among some Chinese against their country's unpredictable traditional ally.

Ties between the sides have been deteriorating for years, although Kim made a long-anticipated visit to Beijing last month after China's implementation of United Nations economic sanctions reduced trade between them by as much as 90 percent.

The quakes that followed the September test were not man-made and didn't appear to cause any damage in the area. The region isn't one where earthquakes naturally occur and no quakes were detected after the five smaller nuclear tests North Korea has conducted since 2006.

Kune Yull Suh, a professor of nuclear engineering at Seoul National University, warned last year that further tests could threaten to cause a volcanic eruption at Mount Paektu, which is about 60 miles away.

On Saturday, North Korea announced it will close its nuclear testing facility and suspend nuclear and intercontinental ballistic missile tests - a move welcomed by Trump as "big progress" - and which comes ahead of the planned summit between him and Kim.

However, the North stopped short of suggesting it will give up its nuclear weapons or scale back its production of missiles and their related components. </s> BEIJING — Research by Chinese geologists suggests that the mountain above North Korea's main nuclear test site has likely collapsed, rendering it unsafe for further testing and requiring that it be monitored for any leaking radiation.

The findings by the scientists at the University of Science and Technology of China may shed new light on North Korean President Kim Jong Un's announcement that his country was ceasing its testing program ahead of planned summit meetings with South Korean President Moon Jae-in and President Donald Trump.

The results also support some of the findings of an earlier study by another group of Chinese researchers that was published last month by the journal Geophysical Research Letters.

Nuclear explosions release enormous amounts of heat and energy, and the North's largest test in September was believed early on to have rendered the site in northeastern North Korea unstable.

Chinese authorities have said they've detected no radiation risk from samples collected along the border. Calls to those departments were not immediately answered on Thursday.

The data in the latest Chinese study was collected following the most powerful of North Korea's six nuclear device tests on Sept. 3, which is believed to have triggered four earthquakes over the following weeks. The yield of the bomb was estimated at more than 100 kilotons of TNT, at least 10 times stronger than anything the North had tested previously. (The bomb the United States dropped on Hiroshima in 1945 had a yield of about 15 kilotons.)

The University of Science and Technology of China paper, authored by Tian Dongdong, Yao Jiawen and Wen Lianxing, said the first of those earthquakes, which occurred 8 ½ minutes after the explosion, was "an onsite collapse toward the nuclear test center," while those that followed were an "earthquake swarm" in similar locations.

"In view of the research finding that the North Korea nuclear test site at Mantapsan has collapsed, it is necessary to continue to monitor any leakage of radioactive materials that may have been caused by the collapse," the authors said in a summary dated Monday and viewed Wednesday on the university's website.

The study is peer-reviewed and has been accepted for publication by the journal Geophysical Research Letters.

The Chinese study makes sense and is based on well understood research, said Rowena Lohman, a seismologist at Cornell University who wasn't part of the work. She said she believes there's an international effort that monitors these tests for radiation.

A study published last month by the journal, authored by a team led by Liu Junqing at the earthquake bureau in Jilin province along the border with North Korea, found similar results of the Sept. 3 explosion. It described the aftershock that followed seconds later as most likely a "rapid destruction of an explosion-generated cracked rock chimney due to cavity collapse."

North Korea's nuclear tests are of special concern to Beijing, since the test site near the town of Kilju is less than 60 miles from the border with China.

North Korean nuclear tests have caused seismic events in Chinese border towns and cities, forcing evacuations of schools and offices, sparking fears of wind-born radiation and leading to a backlash among some Chinese against their country's unpredictable traditional ally.

Ties between the sides have been deteriorating for years, although Kim made a long-anticipated visit to Beijing last month after China's implementation of United Nations economic sanctions reduced trade between them by as much as 90 percent.

The quakes that followed the September test were not man-made and didn't appear to cause any damage in the area. The region isn't one where earthquakes naturally occur and no quakes were detected after the five smaller nuclear tests North Korea has conducted since 2006.

Kune Yull Suh, a professor of nuclear engineering at Seoul National University, warned last year that further tests could threaten to cause a volcanic eruption at Mount Paektu, which is about 60 miles away.

On Saturday, North Korea announced it will close its nuclear testing facility and suspend nuclear and intercontinental ballistic missile tests — a move welcomed by Trump as "big progress" — and which comes ahead of the planned summit between him and Kim.

However, the North stopped short of suggesting it will give up its nuclear weapons or scale back its production of missiles and their related components. </s> North Korea's main nuclear testing site poses a serious risk of radiation leakage after five successive bomb tests caused a mountain to collapse, Chinese geologists say.

The notorious facility has been ruled unsafe for future testing and authorities have been urged to monitor "leakage of radioactive materials", a study found.

Issuing their warning, the authors of the paper - Tian Dongdong, Yao Jiawen and Wen Lianxing - said careful attention should be paid to any radioactive leaks following "research finding that the North Korea nuclear test site at Mantapsan has collapsed".

The study was by China's university of science and technology, which collected data following North Korea's most powerful bomb test on September 3.

Experts believe the estimated 100 kilotons of TNT explosion triggered an initial collapse of the site, followed by an "earthquake swarm" over several weeks, reports Sky News.

It's not the first time nuclear tests have concerned Chinese geologists - the site is a mere 100km from the border.

And there are fears further testing could threaten volcanic eruption at Mount Paektu, on the North Korea-China border.

Just days ago, North Korean leader Kim Jong-Un promised the country would stop conducting nuclear and intercontinental ballistic missile tests.

It is believed he made the vow ahead of his meeting with Donald Trump.

Kim said his country no longer needed to conduct tests because it has completed its goal of developing nuclear weapons.

“To guarantee suspension of nuclear tests in a transparent manner, the republic’s northern nuclear test site will be abolished," state media Korean Central News Agency (KCNA) said.

“The overall projects of the party and the country will be geared towards building of a socialist economy, and all our efforts will be made towards it."

The North's state media, on Saturday, said the nuclear test site would be abolished in order to pursue economic growth and peace on the Korean peninsula.

North Korea also said it would engage in talks with the international community, paving the way for the summit with South Korean President Moon Jae-in planned for tomorrow and a meeting with Donald Trump in late May or early June.

Trump welcomed the news and said he is looking forward to the summit with Kim.

"North Korea has agreed to suspend all Nuclear Tests and close up a major test site. This is very good news for North Korea and the World - big progress! Look forward to our Summit," Trump said on Twitter.

The President has said the US respects North Korea, and this was recipricated.

His comment came after "direct talks at very high levels, extremely high levels" with North Korean leader Kim, he said..

Trump had sent the US Secretary of State to the country for a top-secret meeting over Easter.

The UK Government said in a ­statement: “We hope this indicates an effort to negotiate in good faith.

"A long-term commitment to halt all nuclear tests and ICBM launches would be a positive step.

“We remain committed to working with our international partners to bring about our goal of a complete, verifiable and irreversible denuclearisation of the Korean peninsula, and to do so through peaceful means.”

Tomorrow's historic summit between North and South Korea will discuss nuclear ambitions of the North.

It'll be the first time summit between the two countries in a decade. </s> PUNGGYE-RI, North Korea — North Korea carried out what it said is the demolition of its nuclear test site Thursday, setting off a series of explosions over several hours in the presence of foreign journalists.

The explosions at the nuclear test site deep in the mountains of the North’s sparsely populated northeast were centered on three tunnels at the underground site and a number of buildings in the surrounding area.

The planned closing was previously announced by leader Kim Jong Un ahead of his planned summit with U.S. President Donald Trump that is scheduled to take place next month.

The demolition came as the North lobbed another verbal salvo at Washington, calling Vice President Mike Pence a “political dummy” and saying it is just as ready to meet in a nuclear confrontation as at the negotiating table.

The North’s decision to close the Punggye-ri nuclear test site has generally been seen as a welcome gesture by Kim to set a positive tone ahead of the summit.

Even so, it is not an irreversible move and would need to be followed by many more significant measures to meet Trump’s demands for real denuclearization.

By bringing in a small group of television journalists and other members of the news media, the North is likely hoping to have dramatic images of the closing — including explosions to collapse tunnel entrances — broadcast around the world.

The North did not invite international nuclear weapons inspectors to the ceremony.

The first blast visiting journalists witnessed happened about 11 a.m. local time. North Korean officials said it collapsed the north tunnel, which was used for five nuclear tests from 2009 to last year.

Two other explosions about 2:20 p.m. and 4 p.m. demolished the west and south tunnels, according to officials.

Thursday’s demolition also involved the destruction of observation posts and barracks used by guards and other workers at the facility.

Another tunnel on the eastern side of the facility was shut down after an initial nuclear test in 2006.

The journalists who were allowed to witness the demolition arrived in the morning and stayed at the site for about nine hours.

Getting to the remote site required an 11-hour overnight train journey from Wonsan, a port city east of the capital, Pyongyang.

The outburst at Pence, issued in the name of a top Foreign Ministry official, comes on the heels of another sharp rebuke of Trump’s newly appointed national security adviser, John Bolton, and has raised concerns that a major gap has opened between the sides just weeks before the June 12 summit in Singapore.

In both cases, Pyongyang was trying to push back against hard-line comments suggesting North Korea might end up like Libya if it doesn’t move forward quickly and irreversibly with concrete measures to get rid of its nuclear weapons.

Choe Son Hui, a vice minister of foreign affairs, was quoted Thursday by the North’s state-run news agency slamming as “ignorant” and “stupid” comments Pence made in an interview with Fox News that compared the nuclear-capable North to Libya.

Libya gave up its program at an early stage only to see its longtime dictator overthrown and brutally killed years later.

The summit plan has hit a number of speed bumps recently as both sides have begun trading barbs and taking tougher positions.

Trump met with South Korean President Moon Jae-in on Tuesday at the White House for consultations and suggested the summit could be delayed or even called off entirely.

Even so, both sides still seem to want to hold the meeting, which would be unprecedented.

Success in talks would be a huge accomplishment for Trump. Meeting with the U.S. president as an equal on the world stage would be a major coup for Kim. </s> An earthquake measuring 5.6 on the Richter scale was detected around North Korea’s nuclear test site on Sunday, the Seoul military said indicating that Pyongyang has conducted its sixth nuclear test.

The artificial quake wave was detected around the Punggye-ri site in the North Hamgyeong province, according to the Joint Chiefs of Staff.

The military said it was analysing whether the temblor came from a nuke test, reports Yonhap News Agency.

Seoul’s weather agency said that the seismic wave was recorded at 12.36 p.m.

The USGS said the epicentre was recorded 24 km east-northeast of Sungjibaegam and zero km deep.

South Korean President Moon Jae-in has convened an emergency National Security Council (NSC) meeting following the earthquake and a report by North Korean state-media that Kim Jong-un inspected a hydrogen bomb being loaded into a new intercontinental ballistic missile (ICBM) after it claimed to have made a “more developed nuke”.

Since 2006, North Korea has carried out five nuclear tests, including two last year. </s> • North Korea's primary nuclear test site remains "fully operational" and could be used for further testing in the future, according to a report released Monday.
• Monday's report comes after North Korean leader Kim Jong Un made the announcement on April 20 that his regime would cease its nuclear and long-range missile tests and close the mountainous Punggye-ri nuclear test site, where the regime has conducted all six of its nuclear tests.
• Some experts have suggested that another test at the Punggye-ri nuclear test site could totally destroy it and potentially even cause a mountain to collapse.

North Korea's primary nuclear test site remains "fully operational" and could be used for further testing in the future, 38 North, a watchdog dedicated to analyzing the rogue state, warned Monday.

"North Korea’s Punggye-ri nuclear test site, where North Korea has conducted six acknowledged underground detonations is still, as far as we can tell, fully operational," 38 North reported.

Following North Korea's sixth nuclear test in September, commercial satellite imagery reportedly revealed significant tunneling in one area of the site up until early March. This activity appeared to slow down toward the end of March, but did not stop entirely into early April. According to 38 North, this suggests "that either the tunnel was complete and ready for future renewed testing or that the slowdown simply mirrored the ongoing political changes underway."

With that said, some experts have suggested another test at the Punggye-ri nuclear test site could totally destroy it and potentially even cause a mountain to collapse.

Monday's report comes after North Korean leader Kim Jong Un made the announcement on April 20 that his regime would cease its nuclear and long-range missile tests and close the mountainous Punggye-ri nuclear test site, where it has conducted all six of its nuclear tests.

"From April 21, North Korea will stop nuclear tests and launches of intercontinental ballistic missiles," the Korean Central News Agency said, according to the Seoul-based Yonhap News Agency. "The North will shut down a nuclear test site in the country's northern side to prove the vow to suspend nuclear test."

Kim's announcement was met with applause by President Donald Trump, who took to Twitter on Friday and described the move as "Progress being made for all!"

Trump is set to meet with Kim to discuss the rogue state's nuclear program in the near future, though on Sunday he tweeted, "We are a long way from conclusion on North Korea, maybe things will work out, and maybe they won't - only time will tell....But the work I am doing now should have been done a long time ago!" In a separate tweet on Sunday, Trump incorrectly claimed Kim's regime had "agreed to denuclearization" — North Korea has not indicated it will give up its existing nuclear weapons.

North Korea conducted a slew of long-range missile tests last year as part of its larger ambitions to develop a nuclear weapon capable of reaching the mainland US. This generated outrage across the international community and resulted in harsh economic sanctions being leveled against Pyongyang. But the tide began to shift in early 2018 as North and South Korea, historic enemies, renewed dialogue for the first time in roughly two years. This has also led to a cautious warming of relations between Pyongyang and Washington. </s> North Korea is reportedly preparing its Punggye-ri nuclear test site for international inspectors.

The development was reported by South Korea's Yonhap news agency, citing the country's spy agency.

In May, Sky's Tom Cheshire was the only British broadcaster invited to witness the apparent demolition of the facility, although no inspectors were present.

He watched a series of explosions with North Korea state media claiming the site had been completely dismantled in the blasts "to ensure the transparency of discontinuance of nuclear test".

At the time, the deputy director of the North Korea Nuclear Weapons Institute told Sky News that the destruction of the facility had been "conducted with high levels of transparency" in a bid to bring "peace and stability" to the Korean peninsula and the world.

The unnamed official added: "The discontinuance of nuclear tests is an important process in moving towards global nuclear disarmament and we will continue to join hands with all peace-loving people in building a peaceful world, a new independent world where the dreams and ideals of humanity are realised."

The Punggye-ri facility was used for several nuclear weapons tests, including a suspected hydrogen bomb in September 2017.

Following a summit between North and South Korea in September Pyongyang agreed to allow international inspectors to observe a "permanent dismantlement" of its other key missile facilities, and would take additional steps such as closing its main Yongbyon nuclear complex, but only if the United States took "reciprocal measures".

South Korean president Moon Jae-in said he and North Korean leader Kim Jong Un had agreed that the Korean Peninsula should turn into a "land of peace without nuclear weapons and nuclear threats". </s> North Korea is preparing to allow international inspectors into its Punggye-ri test site, the Yonhap news agency reported on Wednesday, citing a South Korean politician.

Pyongyang has stopped its nuclear and missile tests over the past year during a rapprochement with the United States and South Korea, and it blew up facilities at Punggye-ri in May in the presence of foreign journalists.

However, its refusal to allow international experts to observe the destruction of the site, which has been the staging ground for all six of its nuclear tests, including its most powerful one – reportedly of an H-bomb – last September, drew criticism that its actions were for show and could be reversed.

At a summit between the North and South’s leaders last month, Pyongyang finally agreed to allow foreign inspectors to observe a “permanent dismantlement” of key missile facilities, and to move towards closing its main Yongbyon nuclear complex in return for reciprocal US measures.

News of the apparent latest gesture came from Kim Min-ki, a member of the ruling Democratic Party, who told reporters in Seoul that intelligence officials had observed what they believed to be preparations for possible inspections at Punggye-ri and the Sohae Satellite launching ground.
Scientists from the University of Science and Technology of China state that North Korea's nuclear test site, the Punggye-ri Nuclear Test Site at Mount Mantap, would have collapsed just minutes after the country performed its sixth nuclear test and opened up a hole of up to 656 feet (200 m) in diameter. It has been one of the possible reasons given for North Korea agreement to suspend nuclear and missile tests.