An energetic eruption started on 25 May 2015 from a circumferential fissure at the summit of Wolf volcano on Isabela Island, western Galápagos. Further eruptive activity within the Wolf caldera followed in mid-June 2015. As no geodetic observations of earlier eruptions at Wolf exist, this eruption provides an opportunity to study the volcano's magmatic plumbing system for the first time. Here we use interferometric synthetic aperture radar (InSAR) data from both the Sentinel-1A and ALOS-2 satellites to map and analyze the surface deformation at four time periods during the activity. These data allow us to identify the two eruption phases and reveal strong coeruptive subsidence within the Wolf caldera that is superimposed on a larger volcano-wide subsidence signal. Modeling of the surface displacements shows that two shallow magma reservoirs located under Wolf at ~1 km and ~5 km below sea level explain the subsidence and that these reservoirs appear to be hydraulically connected. We also suggest that the transition from the circumferential to the intracaldera eruption may have involved ring fault activity.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Paul Segall (Stanford University), Charles Williams (GNS Science), and Geoff Wadge (University of Reading) for sharing the topography-correction codes. We also thank Renier Viltres (KAUST), Fabio Corbi (GFZ Potsdam), Eleonora Rivalta (GFZ Potsdam), Valerie Cayol (CNRS), Benjamin Bernard (IGEPN), and Patricio Ramon (IGEPN) for useful discussions. We used Generic Mapping Tools (GMT) to prepare Figure 1. The ALOS-2 data were provided by JAXA and the Sentinel-1A data by ESA/Copernicus. The research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST).