THE 12 FEBRUARY 2013 NORTH KOREA’S UNDERGROUND NUCLEAR TEST AND SEISMOLOGICAL CONTROL OF NUCLEAR TEST BAN TREATY

Abstract

On 12 February 2013, North Korea performed an underground nuclear test that caused an earthquake with magnitude 5.1, which corresponds to an explosion of 6–7 kilotons of TNT. This test followed the previous ones in 2006, which caused an earthquake of magnitude 4.3 (0.5 kilotons of TNT) and in 2009 with magnitude 4.7 (2.4 kilotons of TNT). According to the international Nuclear Test Ban Treaty from 1996, which was not signed by North Korea, such tests are forbidden. International community supervises the respect of the treaty through the monitoring of CTBTO organisation, which is based mainly on seismological observations, but includes also hydroacoustic and infrasound observation, as well as analyses of radionuclides in the air. The spectral ratios between different kinds of seismic waves of an explosion are significantly different from the characteristic of natural earthquakes. Their analysis is therefore one of the principal methods for discrimination. The explosion's yield can also be estimated exclusively from the seismological determined magnitude. The 2013 North Korea’s nuclear test was detected by seismological stations located all around the world, including Slovenia. The travel time of seismic waves to Ljubljana, which is located at the distance of 8360 km measured along the Earth's surface, was 11 minutes and 43 seconds.