Evaluation of Evidence for Volcanic Connectivity in the Galapagos from Satellite Radar Displacements

We use multi-decadal satellite radar displacement measurements to assess the extent of correlations in displacements at Galápagos volcanoes. The Western Galápagos are amongst the most volcanically active areas on Earth, consisting of six major volcanic centres: Alcedo, Cerro Azul, Darwin, Fernandina, Sierra Negra, and Wolf. Five of these volcanoes have erupted since 1990, and ground deformation has been observed at all of them over the same period. Their remote location, and high levels of extrusive activity, have made the Galápagos a prime target for remote sensing techniques such as Interferometric Synthetic Aperture Radar (InSAR). While high magnitude and co-eruptive deformation is characteristic of Galápagos volcanoes, subtle deformation trends at multiple volcanoes points to causal connectivity. For example, GPS measurements suggest that the deformation rate at Sierra Negra changed during the 2008 eruption of Cerro Azul, while seismicity and InSAR observations indicate connectivity between Fernandina, Alcedo, Darwin and Wolf from 20062010. Previous work has also identified lavas with compositional similarities to those erupted at neighbouring volcanoes. Here, we revisit these observations, and extend the observed period using Sentinel-1 InSAR from 2015 to the present. Visual inspection of these Sentinel-1 time series shows coincident changes in deformation, at various volcanoes, during at least five periods from 2015 to 2021. We quantitatively test the significance of these apparent periods of related deformation using cross correlation, and temporal Independent Component Analysis. We corroborate our visual analysis by identifying temporal components of deformation that are active at multiple Galapagos volcanoes. We evaluate the origins of apparent correlations in deformation time series in the Galapagos. Our use of both ascending and descending imagery, in multiple datasets, allows us to dismiss artefacts such as the impact of a common reference point or correlated atmospheric contributions. We test the potential of static stress changes due to major eruptions and intrusions to affect deformation at neighbouring volcanoes using Coulomb stress modelling. Finally, we evaluate the possibility of a common magmatic source driving local displacements at multiple Galápagos volcanoes.