A nuclear detonation detection system (NDDS) is a device or a series of devices that are able to indicate, and pinpoint a nuclear explosion has occurred as well as the direction of the explosion. The main purpose of these devices or systems was to verify compliance of countries that signed nuclear treaties such as the Partial Test Ban treaty of 1963 (PTBT) and the Treaty of Tlatelolco.
There are many different ways to detect a nuclear detonation, these include seismic, hydroacoustic, and infrasound detection, air sampling, and satellites. They have their own weaknesses and strengths, as well as different utilities. Each has been used separately, but at present the best results occur when data is used in tandem, since the energy caused by an explosion will transfer over to different mediums.
Seismic
Seismic networks are one of the possibilities of detonation detection. During an above ground nuclear explosion, there will be a blooming mushroom in the sky, but there will also be a vibration through the ground that spreads for a long distance. In the 1980s, nuclear weapons testing was moved below ground. Even then, it is hard to detect, and especially tricky when the explosion has a small yield. With a seismic network, detection of these nuclear tests is possible.
The Partial Test Ban Treaty (PTBT) banned nuclear testing in the atmosphere, underwater, and in outer space. The U.S. developed many different devices to ensure the Soviet Union was upholding its part of the treaty. The PTBT aimed to ban underground testing as well, but at the time the technology could not detect detonations very well with seismographs, let alone differentiate them from earthquakes making underground tests more difficult to identify than detonations in the atmosphere or underwater. Larger yields could be differentiated but the smaller ones could not be. Even then larger explosions could be dampened by a larger cavity in the ground. With the threat of the Soviet Union conducting underground detonations the U.S. pumped money into seismology research.
A major advance was made by Sheridan Speeth who changed the seismographs data into audible files. One could differentiate between earthquakes and nuclear explosions just by listening to the difference. However, due to his political beliefs his work was ignored. The main system for detecting underground detonations continued to require large numbers of monitoring stations. Due to the difficulty in creating technology and the number of stations needed the PTBT allowed underground testing.
Hydroacoustic
There are 11 hydroacoustic stations that are set up to monitor any activity in the oceans. They were developed to ensure the ban on underwater testing, and because of water’s ability to carry sound they are very efficient. These stations collect data in real time, work 24 hours a day for 365 days a year. However, hydroacoustics have difficulties pinpointing the location of an explosion or event, so they must be used with another method of detection finding(such as the ones previously mentioned). Other problems that hydroacoustics face are the difficulties caused by the structure of the sea floor, as well as islands that can block sound. Sound travels the best through deep ocean, so events near shallow water will not be detected as well. However, hydroacoustic devices also serves different purposes and are used as a unique resource for research on ocean phenomena.
Infrasound
Infrasound works by having multiple stations that use microbarometers to listen for infrasonic waves caused by explosions, volcanoes or other natural occurring events. As with other detection methods, infrasound was developed during the Cold War. These stations were designed to detect explosions with forces as low as 1 kiloton. But after the PTBT, atmospheric detonation detection was left to satellites. Although infrasound waves could travel across the earth multiple times they are very prone to being influenced by the wind and by temperature variations. Sources of long range infrasonic waves are difficult to differentiate (e.g. chemical explosion vs. nuclear explosion).