High hopes for peace on Korean Peninsula
▶ North Korea’s biggest blast set off earthquake and rendered facility unusable, Chinese scientists say
South Koreans with placards of South Korean President Moon Jae-in and North Korean leader Kim Jong-un during a rally on Thursday to celebrate the planned Inter-Korean Summit on Friday. There is great hope the meeting will lead to improved relations between the two countries, who have been at loggerheads since the end of the Korean War in 1953.
The mountain above North Korea’s main nuclear testing site probably collapsed after a test last year, rendering it unsafe for further use and requiring that it be monitored for any leaking radiation, a study by Chinese geologists has found.
Their findings shed new light on North Korean leader Kim Jong-un’s announcement last Saturday that his country will halt its testing programme ahead of planned meetings with the South Korean and US presidents.
The study by scientists at the University of Science and Technology of China supports some of the findings of another group of Chinese researchers that were published last month by the journal Geophysical Research Letters.
The data in the latest Chinese study was collected after the most powerful of North Korea’s six nuclear tests, on September 3. This test is believed to have triggered four earthquakes over the following weeks and rendered the Punggye-ri testing site in north-eastern North Korea unstable.
The yield of the bomb was estimated at more than 100 kilotonnes of TNT, at least 10 times stronger than anything the North had tested previously. In comparison, the US bomb dropped on Hiroshima in 1945 had a yield of about 15 kilotonnes.
The first of those earthquakes, which occurred eight and a half minutes after the explosion, was “an on-site collapse toward the nuclear test centre”, while those that followed were an “earthquake swarm” in similar locations, wrote Tian Dongdong, Yao Jiawen and Wen Lianxing in their paper.
“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 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 was not part of the work. She said she believes there is an international effort to monitor these tests for radiation.
Chinese authorities said they had detected no radiation risk from samples collected along the border.
A study published last month by the journal, written by a team led by Liu Junqing at the earthquake bureau in Jilin province, which borders North Korea, found similar results after the September 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 100 kilometres from the border with China.
North Korean nuclear tests have caused seismic events in Chinese border towns and cities, forcing the evacuation of schools and offices, sparking fears of windborne radiation and leading to a backlash among some Chinese against their country’s traditional, yet unpredictable, ally.
Ties between the two have been deteriorating for years, although Mr 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 per cent.
The quakes after the September test did not appear to cause any damage in the area. The region is not one where earthquakes naturally occur.
Kune Yull Suh, a professor of nuclear engineering at Seoul National University, said last year that further tests could cause a volcanic eruption at Mount Paektu, only 100km 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 US President Donald Trump as “big progress” ahead of the planned summit between he and Mr Kim.
But the North stopped short of suggesting it would give up its nuclear weapons or scale back its production of missiles and related components.
North Korea’s nuclear tests are of concern to Beijing, since the test site near the town of Kilju is less than 100km from the border with China