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Trapdoor Faulting and Initiation of the 2018 Eruption at Sierra Negra Volcano, Galápagos Islands

Zilin Song1, 2, Andrew Bell2, Sophie Butcher2, 3, Mario Ruiz4, Peter La Femina5, Stephen Hernández4, Patricia Gregg6, and Yen Joe Tan1

  • Affiliations:  1Department of Earth and Environmental Sciences, The Chinese University of Hong Kong, Hong Kong S.A.R., China; 2School of Geosciences, University of Edinburgh, Edinburgh, UK; 3British Geological Survey, Edinburgh, UK; 4Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador; 5Department of Geosciences, The Pennsylvania State University, State College, PA, USA; 6Department of Earth Science & Environmental Change, University of Illinois at Urbana--Champaign, Champaign, IL, USA

  • Presentation type: Poster

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

  • Poster Board Number: 110

  • Programme No: 2.1.20

  • Theme 2 > Session 1

Abstract

At the basaltic calderas of the western Galápagos Islands, large intra-caldera earthquakes have been commonly observed closely preceding eruption onset. The nature of earthquake-eruption interaction likely plays a role in eruption initiation, yet the specific mechanisms remain enigmatic. Here we analyze microseismicity to show that the initiation of the 2018 eruption of Sierra Negra involved a complex cascading process lasting over ten hours. The co-seismic stress changes from a Mw 5.4 trapdoor faulting earthquake did not immediately promote failure of the magma reservoir, as happened for the 2005 eruption. Instead, the emergence of repeating long-period earthquakes (LPs) families indicates a cryptic phase of reservoir failure, ultimately culminating in dyke propagation and eruption. Our results indicate that a primed magmatic system and favorable co-seismic stress changes may not be sufficient to cause reservoir failure and suggest that such eruptions can be harder to forecast than currently thought.