North Korea's nuclear test altered the structure of a mountain

Between 13 and 16 times the size of the bomb dropped on Hiroshima in 1945. That was the sixth and largest nuclear test conducted by North Korea so far. Although the country has been able to shield itself from leaking information on much of its military and nuclear activities, scientists have found a way to at least partly identify the extent of the damage.

The blast was conducted in an underground tunnel beneath Mount Mantap, located almost 650 km from Pyongyang, the country's capital. According to North Korean President Kim Jong-un, the blast was from a hydrogen bomb and was successful - whatever that means.

In practice, the mountain is still whole, but has moved more than 3 meters sideways, losing almost 1 meter in height. It's almost as if someone had crumpled it down, spreading it out a little and widening its diameter, according to seismologist Roland Burgmann of the University of California.

It was he who even conducted a study to try to map the size of the damage, even without access to the bombed territory. It turns out that it is possible to measure the impact of the fall of an atomic bomb using the same parameters applied to measure earthquakes - no wonder the researcher who performed the analysis was a seismologist.

In September 2017, a test also conducted by North Korea caused an earthquake equivalent to a 6.1 magnitude quake.

The analysis is made from a measurement of the types of seismic waves generated and in which direction these waves go. On September 2017, seismologists were able to identify that it was caused by a nuclear explosion. They even estimated that the explosion of the time was 23 times greater than the Hiroshima bomb.

This time, the German TerraSAR-X satellite was able to capture high-resolution images by comparing the before and after Earth's surface in that region. With this they were able to determine where the blast began and to realize that the terrain had moved.

"We were really surprised by the size of the horizontal movements and how few vertical movements were, " says study author Doug Dreger, a seismologist at the University of California, Berkeley, on The Verge.

In the case of this new test, the explosion had an impact equivalent to exploding between 171 and 209 tons of TNT in a tunnel about 450 meters below the top of Mount Mantap.

The detonation of the bomb melted and vaporized the rock around the tunnel and caused the mountain to fall into the cavity where it was detonated. It also gave scientists an idea of ​​the composition of the terrain: probably some kind of granite.

About 8 1/2 minutes after this first explosion, there was a second tremor, which was probably caused by the implosion of the tunnel.