Detecting Secret Nuclear TestsDuring the period between 1945 and 1996 (the comprehensive nuclear test ban treaty was introduced), it is estimated that over 2000 nuclear tests were conducted. The treaty enabled the international monitoring system established by the UN to monitor secret nuclear explosions in four methods:
The explosive tests conducted after 1962 were underground to ensure testing functions are not detected. Fortunately, a worldwide system to detect earthquakes and seismic activity was available which could be used to detect nuclear denotation. The shock waves caused by nuclear tests are strong. Tracking seismic data would facilitate detailed investigation.
Water can conduct sound. Monitoring stations (middle of a water body/offshore) with microphones have been established in strategic locations - Pacific, Atlantic and Indian Ocean to transfer data back to continental stations.
Since mega chemical and nuclear explosions generate low frequency sound waves that travel through the atmosphere, the sound waves can be used for detection. There are stations located across global destinations to monitor the low frequency waves. These sound waves are below the threshold of human hearing (917 Hz and less).
It is the oldest and an optimal method to detect secret nuclear operations by tracking radioactive chemicals in the atmosphere. Radionuclide detection is advanced at present. Monitoring stations located across the atmosphere can detect the existence of radioactive isotopes expeditiously. The stations have the infrastructure to monitor noble gases, thereby assisting in detecting underground nuclear tests - isotopes of xenon and argon can be found in the environment over a period of time.
Using the Global Positioning System
The system that enables travelers across the globe to navigate also identifies secret nuclear tests. Though it may not be part of an International Monitoring System, the network of commercial global positioning satellites is contributing to monitoring nuclear tests. For e.g.: during the nuclear test conducted by North Korea in 2009, an increase in atmospheric electron density was received by GPS (South Korea) in the surrounding area.