Thanks to a new imaging technique, researchers can see into the bowels of a volcano

This new method is based on the arrangement of a network of listening instruments which capture not only the strong tremors of earthquakes, but also seismic noise.

What exactly happens under a volcano when it is not erupting? A team of CNRS researchers has managed to discover it, thanks to a new imaging technique. Their work was published on Monday, September 16, in the journal Nature. These researchers have succeeded in very concretely recreating in image the structure of the Soufrière volcano in Guadeloupe, as if they had been able to see through the ground, up to 10 km deep. They saw the “plumbing” system of the volcano, with the presence of a five-kilometer-long chimney, a little tortuous and below pockets of magma. They are side by side or superimposed and connected to each other. This is the first time that scientists have succeeded in establishing this diagram, with an accuracy of 100 meters.

It’s all based on a technique called matrix imaging. The principle is to listen to seismic noise, thanks to sensors installed on the volcano. Here, the team used 76 geophones, a bit like seismometers, to “listen for two months to how the seismic noises of the Soufrière volcano evolve”says Alexandre Aubry, research director at the Langevin Institute in Paris. By then studying how these waves echoed among themselves and resonated with the different materials found in the ground deep down, these scientists deduced the pattern of the deep structure of the volcano, with its conduits and pockets of magma. This technique has already been used to better understand faults in the Earth’s crust, but not to study volcanic activity.

This discovery can be useful to better anticipate eruptions, because eruption predictions are mainly based on the location and pressure created by the magma. Since this imaging technique allows to precisely locate these pockets under the volcano, which has never been done before, it is quite revolutionary to improve eruption predictions.

This type of monitoring and imaging technique can be implemented in an emergency. Two days of seismic noise measurement can be enough. Most volcanoes in the world already have seismic sensors permanently installed.