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Magma accumulation and asymmetric ring-fault activity preceding the 2024 eruption of Fernandina volcano, Galápagos Islands

Andrew Bell1, Susanna Ebmeier2, Stephen Hernandez3, Christopher Bean4, Peter La Femina5, and Mario Ruiz3

  • Affiliations:  1School of GeoSciences, University of Edinburgh, Edinburgh, U.K; 2School of Earth and Environment, University of Leeds, Leeds, U.K.; 3Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador; 4Dublin Institute for Advanced Studies, Dublin, Ireland; 5Alfred Wegener Institute, Helmholtz Center for Polar & Marine Research, Bremerhaven, Germany

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 13

  • Programme No: 1.5.20

  • Theme 1 > Session 5

Abstract

At caldera volcanoes, ring faults can play a key role in controlling the dynamics of eruptions and patterns of associated deformation and seismicity. However, we have less understanding as to how these structures can influence the nature of eruption precursors and shape the process of eruption initiation. Here we show that the March 2024 eruption of Fernandina, a frequently-active basaltic caldera volcano in the Galápagos Islands, Ecuador, was preceded by a 2.5-year episode of magma accumulation, driving surface uplift and asymmetric seismicity on a ring fault system. Analyses of data from a local hybrid seismic network-array, and satellite-derived deformation measurements, reveal: (1) that rates of volcano-tectonic earthquakes at Fernandina increased progressively with surface uplift from November 2021 until the end of April 2023; (2) the subsequent ten months of unrest involved a sequence of short-duration uplift and seismicity pulses; and (3) a final unrest pulse, starting in late February 2024, included a Ml 4.4 earthquake on 2nd March, followed 20 hours later by the initiation of an intense, laterally-migrating seismic swarm. This swarm culminated after two hours with the onset of the eruption on a set of fissures on the SE caldera rim. Earthquake source locations suggested asymmetric activity of the ring fault system at depths of 4--6 km, between shallow and intermediate-depth inflation sources. These observations suggest a complex interplay between the magmatic plumbing and ring fault systems at Fernandina and reveal important differences in behavior with previous eruptions at Fernandina and elsewhere in the Galápagos.