Seismology is a branch of science that most people associate primarily with earthquakes. However, seismic waves are generated from a variety of sources beyond tectonic activity such as industrial accidents, mining operations, explosions, and traffic. Whatever might be the cause of seismic wave, it can be recorded by instruments called seismographs.
For decades, the international seismological community has played a key role in monitoring nuclear tests, particularly underground detonations. The physical characteristics of an explosion differ from those of a natural earthquake, which results from two blocks of the Earth’s crust slipping past one another. In contrast, an explosion releases energy outward from a single point source. These differences in physics produce dissimilar seismic waveforms, allowing seismologist to distinguish between earthquakes and explosions.
A notable example of seismology’s broader utility occurred on September 26, 2022, when an underwater explosion caused a gas leak in the Nord Stream pipeline near the Danish island of Bornholm. The first blast, at 02:03 Central European Time, was automatically detected and classified as a likely explosion by the Danish and Swedish national seismic networks within a minute. The same rapid detection applied to the second explosion at 19:03 UTC. These seismic waves traveled through the bedrock and were detected with seismographs thousands of kilometers from the source.
Seismographs are also recording explosions related to the war in Ukraine that Russia started 2022. In April 2025, the destruction of an ammunition depot in Russia’s Vladimir region generated seismic events of magnitudes 3.4 and 3.2. Estimating the explosive yield from seismic magnitude is more complex for surface blasts, as much of the energy escapes into the atmosphere or contributes to fires rather than generating seismic waves traveling through bedrock. Nonetheless, seismological data provides reliable and uncompromised information about large explosions, offering a cost-effective and robust method for monitoring vast regions using civilian infrastructure that is nearly impossible to spoof or jam.
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) maintains a global network of stations capable of detecting seismic events larger than magnitude 4 anywhere in the world. For instance, North Korea’s six nuclear tests between 2006 and 2017 were clearly recorded also in Finland by the FINES station, part of the CTBTO’s International Monitoring System (IMS).
Russia withdrew its ratification of CTBT agreement in 2023 and in November 2025 Russia has floated the possibility of nuclear tests after US president comments on starting testing nuclear weapons. Geopolitical tension in Europe is apparent, and national and regional seismic networks provide additional valuable tools for real-time situational awareness. We need to work to ensure that our capacity to detect violation of CTBT is optimal both technically and in terms of communication and collaboration, both nationally and internationally, especially within NATO.
Traditionally, seismograph stations have been located on land but recent advances in fiber-optic sensing are revolutionizing the field. Laser pulses sent through standard telecommunication fiber-optic cables can detect changes in strain caused by seismic events. This technology enables monitoring along hundreds of kilometers of undersea cables with spatial resolutions down to a few meters. Detected strain changes may result from explosions, passing submarines, or even large marine animals. Fiber-optic seismology offers a promising tool for tracking strategically important activities, such as the movements of so-called ”shadow fleets” in the Baltic Sea.
Planning seismic networks with a regional strategy—rather than within national silos—will enhance detection effectiveness regardless of main interest being on monitoring natural earthquakes or man-made explosions. For defense and civil authorities alike, seismic network forms a powerful tool to create accurate, real-time situational awareness across the Baltic region and information gained from these networks can support timely decision making. The existing seismic station network and related cutting-edge expertise can be utilized as part of overall security protocols of NATO countries.
University of Helsinki
Finland
