Chemical, nuclear blasts can be detected from GPS data
doi:10.1038/nindia.2021.52 Published online 13 April 2021
Data from Global Positioning System (GPS) satellites, used in monitoring deformation in the Earth's crust due to earthquakes, can also help detect large explosions such as chemical or nuclear blasts, according to an Indo-Japanese team of atmospheric scientists1.
When strong surface explosions happen, they excite acoustic waves, which often disturb the upper atmosphere and the ionosphere extending from about 50 km to 1000 km above the Earth's surface. GPS signals from the satellite pass through the ionosphere to reach receivers on the ground. Analysing ionospheric variations of these signals can help in characterizing the explosion event, its source process and mechanism, according to researchers led by Bhaskar Kundu at the Department of Earth and Atmospheric Science, National Institute of Technology, Rourkela in India.
The team used GPS data from a massive explosion that occurred at a chemical warehouse in the Lebanese capital of Beirut on 4 August, 2020 to study the variation of Total Electron Content (TEC) in the ionosphere. The catastrophic explosion — considered one of the most powerful non-nuclear human-made explosion in history — was recorded in Tunisia, Germany, and Ivory Coast, and several seismic stations within a 500 km radius.
The researchers examined data from 15 continuous GPS stations in Israel and Palestine and could see “discernible variation” in TEC in the ionosphere 10 minutes after the explosion — the time necessary for the acoustic wave to reach the 'F-region' of the ionosphere that has the highest concentration of free electrons and ions.
The researchers report a "peak-to-peak amplitude of the disturbance reaching ~ 2% of the background electrons", comparable to recently recorded volcanic explosions in the Japanese Islands.
Acoustic waves excited by explosions have earlier been detected in the ionosphere during mine blasts, volcanic explosions and North Korean underground nuclear tests. The researchers say it is possible to detect large nuclear explosions and chemical blasts using such GPS data.