The September 2021 eruption at Cumbre Vieja volcano (La Palma, Canary Islands): investigation on the pre- and co-eruptive phases through DInSAR measurements and analytical modelling

Since 19 September 2021, an intense eruptive activity has begun at Cumbre Vieja volcano (La Palma, Canary archipelago, Spain), causing huge social and economic damage. The eruption was preceded and accompanied by several phenomena, such as ground deformations and seismic activity. In this work, we analyse the Differential Interferometric Synthetic Aperture Radar (DInSAR) measurements obtained by processing Sentinel-1 images acquired from both ascending and descending orbits, in order to quantify the retrieved pre- and co-eruptive deformation patterns. In particular, we exploit the Advanced DInSAR technique referred to Parallel-Small BAseline Subsets (P-SBAS), showing the importance for oceanic islands, such as La Palma, of investigating DInSAR products retrieved from time series, instead of single interferograms. Indeed, this may allow us to effectively remove possible atmospheric artifacts within the retrieved displacement measurements. Subsequently, we invert the processed DInSAR measurements through analytical modelling with the aim of examining the characteristics of the volcanic sources responsible for the observed deformations. In detail, our results highlight that a sill-like source was active in the pre-eruptive phase (8 – 16 September) and it can be interpreted as the effect of the temporary accumulation of magma during its transport toward the surface. On the other hand, the action of two dikes prevailed during the co-eruptive phase (17 – 22 September), causing the eruptive vent opening. Therefore, our results suggest that a complex network of sills and dikes has allowed the magma rising. Moreover, our findings are in good agreement with the seismicity recorded by the Instituto Geografico Nacional (IGN) network, and several geophysical evidences (i.e., resistivity anomaly, petrographic analyses, computation of the erupted magma volumes, field observations).