After it withdrew from the Treaty on the Non-Proliferation of Nuclear Weapons in 2003, North Korea began conducting several increasingly intense underground nuclear weapon tests in 2006, culminating in the largest nuclear bomb testing in September 2017.
To get a clearer picture of changes to the Earth’s surface and underground at the test site, an international research team, including Asst Prof Wei Shengji of NTU’s Asian School of the Environment and colleagues from Germany, the US and China, analysed records from seismometers deployed in surrounding countries, in combination with satellite radar imagery.
Using before and after satellite images, seismic data and the modelling of these observations, the team found that the top of Mount Mantap, located in an inaccessible area of North Korea, experienced a successive rise, collapse and compaction, ultimately moving by about 3.5 meters horizontally and about 0.5 meters vertically.
The researchers also determined that the explosive power of the nuclear detonation was equivalent to 120-304 kilotons of TNT—more than ten times the power of the Hiroshima bomb.
“This is the first time the complete 3D surface displacements associated with an underground nuclear test were imaged,” says Dr Wang Teng, a Senior Research Fellow at NTU’s Earth Observatory of Singapore.