Monitoring an active war zone in Ukraine using seismic data

**Monitoring an active war zone in Ukraine using seismic data** Seismic data have been used to continuously identify individual military explosions in Ukraine. Such conflict monitoring provides unprecedented details of these attacks and an objective data source that is essential for accurate war reporting and for identifying potential breaches of international law. This is a summary of: Dando, B. D. E. et al. Identifying attacks in the Russia–Ukraine conflict using seismic array data. Nature https://doi.org/10.1038/s41586-023-06416-7 (2023). **The problem** Objective monitoring and reporting of an active conflict zone are crucial for developing a clear understanding of a conflict — including how it is progressing, who is affected and whether there have been breaches of international law. Despite the unprecedented level of information now available, there is still a lack of comprehensive and objective data sources that are openly accessible. Although satellite images can provide high spatial resolution when showing the results of military attacks (see go.nature.com/3ksfceo), their cost and production rate limit their use for real-time monitoring. Given that today’s global satellite network cannot provide comprehensive coverage across a large region in real time, the incompleteness that hampers conventional reporting still affects satellite data. Seismic and acoustic data collected by a global network of sensors have long been used to monitor nuclear tests1 and to detect large individual explosions2. However, monitoring an active conflict zone, with much smaller explosions, requires a network of sensors close to the attacks. **The solution** A permanent seismic array of 23 sensors is located about 100 kilometres northwest of Kyiv. These seismometers are operated as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which exists to identify nuclear explosions around the world. We took advantage of the positioning of these sensors to implement a continuous monitoring strategy to identify and locate individual military explosions in north Ukraine between January and November 2022. Energy from an explosion can travel both through the atmosphere as acoustic waves and through the ground as seismic ones. By recording these signals with a network of seismometers, we automatically backprojected the energy transmissions to the time and location of their source, resulting in a continuously updating catalogue of explosions. We identified more than 1,200 military explosions between 24 February and 3 November 2022 in the Kyiv, Zhytomyr and Chernihiv provinces of Ukraine, including the time, location and approximate size of each attack (Fig. 1). Comparisons with publicly available reports of military attacks in the region showed that our detections greatly exceeded the number of individual reports. Furthermore, we found clear changes in the intensity of the attacks — including high-intensity bombardments after the initial invasion, the near-cessation of attacks after the Russian withdrawal from the region and the sporadic targeted attacks that followed. Figure 1. Figure 1 | Map of seismic detections in northern Ukraine between January and November 2022. The detected explosions (circles) are coloured by their date of occurrence and scaled by their magnitude (M). The detections from quarry blast made before Russia’s invasion began on 24 February 2022 are shown in grey. The locations of the individual seismic sensors of the Malyn array are shown as white triangles, and the location of the Chernobyl nuclear power plant is indicated. Scale bar, 50 kilometres.Credit: Dando, B. D. E. et al./Nature (CC BY 4.0) **The implications** The implementation of continuous seismic monitoring in an active conflict zone has important implications both for the war in Ukraine and for future conflicts. We now have an objective means of verifying claims of individual attacks in northern Ukraine as well as a new objective source of information for both past and future attacks. Where there are claimed breaches of international law, such data might provide crucial evidence. Although our catalogue of explosions provides a unique picture of the military attacks in northern Ukraine, it cannot be regarded as comprehensive. Explosions far away from the sensors are less likely to be detected and are located with less precision. Similarly, explosions that do not generate substantial seismic energy, such as above-ground detonations, might go undetected. Notably, it is impossible to state, from our observations alone, who is responsible for any given explosion — regardless of the accuracy and precision of the detection. Many opportunities exist to expand this work. For example, machine learning could be used to improve our automatic detections, reducing the need for the manual quality control that is currently performed. Analyses of the signal characteristics might provide information on the types of ammunition used and improve our estimates of the size of the explosion. Moreover, although our detection resolution is the highest in northern Ukraine, we can detect explosions outside this region. Further deployment of both seismic and acoustic sensors could improve conflict monitoring in Ukraine. — Ben D. E. Dando is at NORSAR, Kjeller, Norway. ***Expert opinion*** This work is a first-of-a-kind investigation of conflict-related explosions using local seismic-array data. The authors were able to produce a catalogue of explosions occurring between February and November 2022 that shows a number of events exceeding the number of publicly reported attacks. The authors are experts in signal processing and event detection, and the data processing, event localization and magnitude estimation are robust and state of the art. — A reviewer ***Behind the paper*** NORSAR, an independent research foundation specializing in seismology, began monitoring the war in Ukraine because of its role as an adviser to Norway’s Crisis Committee for Nuclear and Radiological Preparedness. After Russia’s invasion started, there were serious questions about the integrity of the nuclear power plants in Ukraine and a need to ensure that any nuclear incidents could be identified rapidly. As Norway’s national data centre for the CTBTO, NORSAR has long monitored explosions3, and we quickly acquired seismological data from many sources that could help our ability to detect explosions near the power plants. However, once we began analysing data from the Malyn seismic array, we were overwhelmed by the number of explosions that we could observe and accurately locate. It became apparent that we were seeing many more explosions than were being reported and that the seismic data provided a unique source of information. — B.D.E.D. ***From the editor*** Although using seismic arrays to detect and locate explosions is certainly not a new thing, doing so in an active combat zone and in close to real time sets this study apart. The method with which the authors were able to provide an independent analysis of the location and yield of such explosions could be useful for monitoring conflicts in the future. — John VanDecar, Senior Editor, Nature