Scientists Say N. Korea's Nuclear Test Site Likely Collapsed
Chinese researchers say the mountain above North Korea's main nuclear test site has likely collapsed. If so, the collapse would make the test site unsafe for future testing, and the area would need to be examined for any leaking radiation.
Scientists at the University of Science and Technology of China carried out the research. Their findings may give new meaning to North Korean President Kim Jong Un's recent announcement. He said this month that his country was ending its nuclear testing program ahead of planned meetings with the leaders of South Korea and the United States.
The results also support findings of an earlier study by a group of Chinese researchers. That report was published in March by the journal Geophysical Research Letters.
The latest study has also been accepted for publication by Geophysical Research Letters.
What could have happened?
The data in the most recent Chinese study was collected following the most powerful of North Korea's six nuclear device tests, on September 3. That test was at least 10 times stronger than anything the country had tested before. Scientists say the explosion may have helped cause four earthquakes in the following weeks. Earthquakes do not naturally happen in the area around the test site.
The report by University of Science and Technology researchers said the first of those earthquakes was "an onsite collapse toward the nuclear test center." They urged officials to continue to watch for leaks of radioactive material.
Special concern to China
North Korea's nuclear tests are of special concern to China; the test site is less than 100 kilometers from the China-North Korea border.
North Korean nuclear tests have caused seismic events in Chinese border towns and cities. The explosions have led to evacuations of schools and offices, and fears of wind-carried radiation.
Chinese officials have said they have not measured any radiation risk from recent samples collected along the China-North Korea border.
Relations between China and North Korea have been worsening. Last month, North Korean President Kim Jong Un made a visit to Beijing, after Chinese officials put United Nations economic sanctions against the North in place. The sanctions reduced trade between the two countries by as much as 90 percent.
On Saturday, North Korea announced it would close its nuclear testing site and suspend nuclear and intercontinental ballistic missile tests. U.S. President Donald Trump called the moves "big progress."
However, the North did not say whether it would give up its nuclear weapons or limit its production of missiles and their related parts.
I'm Jonathan Evans.
1.nuclear test 核试验
A nuclear test went awry when they underestimated the power of the explosion.
2.give up 放弃
After a fruitless morning sitting at his desk he had given up.
3.as much as 多达
I had to fall in with her wishes as much as possible.
4.seismic events 地震（地球物理学）
More than 10,000 seismic events have been recorded near El Hierro since July 17.
5.The results also support findings of an earlier study by a group of Chinese researchers.
a group of 一组；一群
Suddenly the door opened and a group of children burst in.
I came across a group of children playing.
6.Last month, North Korean President Kim Jong Un made a visit to Beijing, after Chinese officials put United Nations economic sanctions against the North in place.
put in place 落实；实施
They're offended by the elaborate security measures the police have put in place.
On the reforms front, China has put in place the basic structure for a market economy.
中国科学技术大学的科学家进行了这项研究。他们的发现或许为朝鲜领导人金正恩近期的声明赋予了新的意义 。本月，金正恩表示，朝鲜计划在与韩、美领导人会晤前终止核试验 。
中国这项最新研究中的数据是在朝鲜9月3日进行第六次核试验后收集到的。这次核试验强度至少比此前进行的试验强10倍以上 。科学家表示，这次爆炸可能触发了之后数周发生的四次地震 。试验场附近区域的地震并非自然原因所致 。
中国与朝鲜的关系一直在恶化。上个月，在中国官员落实联合国对朝经济制裁后，朝鲜领导人金正恩亲赴北京访问 。制裁导致两国贸易减少了90% 。