Pre- and Co-Eruptive Analysis of the September 2021 Eruption at Cumbre Vieja Volcano (La Palma, Canary Islands) Through DInSAR Measurements and Analytical Modeling

We investigate the 19 September 2021 eruption of the Cumbre Vieja volcano (La Palma, Canary Islands, Spain). In particular, we analyze the Differential Interferometric Synthetic Aperture Radar (DInSAR) measurements obtained by processing Sentinel-1 images acquired from both ascending and descending orbits. First, we show the importance, for oceanic islands like La Palma, of investigating DInSAR products retrieved from time series, instead of single interferograms, to effectively remove possible atmospheric artifacts within the displacement measurements. Subsequently, we invert the retrieved data through analytical modeling. Our results highlight that a sill-like source was active in the pre-eruptive phase (8-16 September), whereas the action of two dikes prevailed during the co-eruptive phase (17-22 September). This evolution suggests a process of magma rising through a network of interconnected sills and dikes. The seismicity, that preceded and accompanied the onset of the eruption, is consistent with our findings.