In September 2017, there is an underground North Korean nuclear test that exploded with ten times the energy of Nagasaki bombs. Also, it caused parts of the mountain peak sink by ½ meter and shift about 3.5m south.
Such are conclusions drawn by the geophysicists who utilized instruments and satellite radar, which pick up waves that travel through the earth for the calculation of the strength and depth of explosion. They also reported some signs that a subterranean tunnel system at a test site collapsed 8.5 minutes after a bomb detonated.
Previously, a synthetic radar aperture imagery, which is a satellite technology mapped how the ground warps and stretches after the earthquakes. However, it’s the first time it was used for examining nuclear bomb test site. This is according to the geophysicist and study co-author, Teng Wang, of Nanyang Technological University in Singapore. He also said that they have never seen a huge displacement caused human activities from the synthetic radar aperture imagery.
In 1996, UN General Assembly adopted Comprehensive Nuclear-Test-Ban Treaty, yet there were 9 nuclear tests that took place. 6 of these were done by North Korea and 5 of them were at the Mt. Mantap facility in the north of the country. The bombs detonated in the chambers tunneled into the mountain, which is a granite peak that extends over 2200m. Yet, this means that the details of every test, like the energy generated by bombs, have been unknown outside the country of North Korea even until now.
Dr. Wang along with his colleagues suspected they might deduce the precise location and strength of the bomb test on the 3rd day of September last year that triggered an earthquake with a magnitude of 6.3.
Clandestine nuclear activities were tracked by the global monitoring system of sensors, which pick up faint shivers as well as shudders that are generated by distant earthquakes and underground blasts. While such instruments can pick up the bomb blast’s wave signature thousands of kilometers away, still, more details are required to pinpoint where the explosion took place.
Weeks after the bomb test of North Korea last September 2017, Dr. Wang together with his colleagues got images of the terrain of Mt. Mantap after and before the test. The images were taken by a satellite, which is German TerraSAR-X. To map the dips and bumps on the entire surface of Earth, TerraSAR-X pings radar to the ground and measured the time it took for the signal to bounce back.
According to Dr. Wang, as long as the ground was deformed, they can measure it from space with the use of synthetic radar aperture. Combined with a little nifty mathematical modeling, the first time that anyone’s modeled an underground nuclear test with the radar data, geophysicists got the detonation site’s exact site.
Other than that, geophysicists found seismic shivers of a smaller event, which is an aftershock that appeared 700m south of and after 8.5 minutes, the explosion. The aftershock produced waves that were not consistent with a bomb explosion. Instead, it looked like the ground already imploded.