The tomographic analysis of 17,345 microearthquakes recorded after its eruption has enabled the creation of a 3D internal map of the Cumbre Vieja volcano on La Palma. This unprecedented work will assist scientists in mitigating risks in the future across other volcanic regions.
This month, the journal Geophysical Research Letters publishes a study led by the Italian National Institute of Geophysics and Volcanology (INGV) and the Canary Islands Volcanology Institute (Involcan) regarding the internal structures of the volcano that began to emerge in the Valle de Aridane on 19 September 2021.
“It was a unique opportunity to observe a newly formed volcano, when its internal structures are still incandescent and active,” explains Luca D’Auria, Director of Volcanic Monitoring at Involcan, in a statement released from Italy by the INGV.
The study employed seismic tomography resources applied to the earthquakes recorded during those days, allowing for the reconstruction of a three-dimensional image of the first 1,500 metres below the volcano. This was achieved through data from a network of 17 temporary seismic stations installed around the cone immediately following the eruption.
These instruments recorded thousands of microseisms over nine months, generated by thermal contraction processes and the movement of gases released from the cooling magma.
“Thanks to artificial intelligence, we were able to analyse over 17,000 microseisms, automatically distinguishing the useful seismic waves,” the researchers highlight.
An “Excellent Indicator”
With all this information, they were able to analyse the velocity patterns of the different seismic waves and their relationships. These measurements are particularly significant as they provide an excellent indicator of the temperature and the presence of fluids.
The results indicate that in the surface layers, the analysed ratio is low, suggesting rocks are porous and saturated with gas or steam; however, at greater depths, the value increases, indicating the presence of liquid fluids.
“This variation informs us about how pressure affects the state of fluids within the volcano: at depth, they remain liquid while higher up, they transition to a gaseous state,” explains Sergio Gammaldi, a researcher at the Vesuvian Observatory of the INGV.
The study also facilitated the identification of the primary magma conduit, the fracture through which the lava and gas ascended during the volcano’s eruption.
A Volcano of 15.62 km³
The image obtained from the depths of Cumbre Vieja encompasses a volume of 15.62 km³ (equivalent to a cube measuring 2.5 kilometres on each side) and is the first of its kind made of a recently formed monogenetic volcano.
The findings highlight the rapid development of the hydrothermal system, comprising groundwater and gas beneath a young volcano, and provide valuable insights for predicting and monitoring future eruptions, not only in La Palma but also in other areas with similar volcanic activity, the researchers emphasise.
“Studying a newly formed volcano from within is not just a scientific challenge; it also enhances our ability to prevent risks in areas inhabited by millions of people,” concludes D’Auria.
