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Published March 2022 | Published + Supplemental Material
Journal Article Open

Precursory Signal Detected for the 2018 Sierra Negra Volcanic Eruption, Galápagos, Using Seismic Ambient Noise

Abstract

The changes in physical properties leading up to a volcanic eruption provide clues to processes occurring within volcanoes and may reveal premonitory signals. The Sierra Negra shield volcano, located in the Galápagos Islands, erupted on 26 June 2018 after months of continued inflation and escalating earthquake activity. We applied ambient noise interferometry to five months of continuous seismic data from 12 broadband stations to calculate crustal shear-wave velocity changes before and during the eruption. Using the Moving Window Cross-Spectral technique and a pre-eruption stack of ambient seismic data as reference, we found a −0.27% decrease in velocity 17 days before the eruption in station-pairs that pass beneath the caldera's north-eastern sector. Sensitivity kernels suggest that the velocity changes of this precursory signal are greatest at depths corresponding to the shallow sill (∼2 km) beneath the wide caldera. Our results, considered in light of geodetic, seismicity, and petrological results, suggest that this velocity decrease is in part caused by dilatation from a M_L 4.8 earthquake, and degassing after a possible magma intrusion below or at the base of the sill. The precursory velocity decrease within the sill region offers an important tool for forecasting future eruptions at Sierra Negra.

Additional Information

© 2022. American Geophysical Union. Issue Online: 10 March 2022. Version of Record online: 10 March 2022. Accepted manuscript online: 24 February 2022. Manuscript accepted: 22 February 2022. Manuscript revised: 18 January 2022. Manuscript received: 10 August 2021. The authors thank Andrew Bell, Christopher Bean, Martin Molhoff, Stephen Hernandez and the rest of the personnel of the IGUANA project (PC3018 and PC10019) for access to data from the temporary stations and field work, and the Instituto Geofísico-Escuela Politécnica Nacional for access to the seismic data from the permanent stations. The permanent seismic network was funded by the project: Generacion de Capacidades para la Difusion de Alertas Tempranas y para el Desarrollo de Instrumentos de Decision ante las Amenazas Sismicas y Volcanicas Dirigidos al Sistema Nacionalde Gestion de Riesgo. The authors thank the Galápagos National Park and its office in Isabela for supporting seismic and geodetic data acquisition activities. MZR thanks the David Simpson fund of the Incorporated Research Institutions for Seismology (IRIS), and the Marshall-Heape Chair that co-sponsored MZR's 2019 summer undergraduate internship, which forms the core of this project. We thank the two anonymous reviewers for comments that improved the manuscript. Data Availability Statement. Raw seismic data from IGUANA project are available from the Incorporated Research Institutions for Seismology (IRIS), Data services (https://doi.org/10.7914/SN/8G_2018) and data from the Ecuadorian national network (https://www.fdsn.org/networks/detail/EC/) on request from the IGEPN at https://www.igepn.edu.ec/datos-mseed. Raw cGPS data are available through the UNAVCO archive: https://www.unavco.org/data/data. html, at: https://doi.org/10.7283/ESJY-V915, https://doi.org/10.7283/FE83-C961, https://doi.org/10.7283/T5N58JM5, https://doi.org/10.7283/FY2B-DV40, https://doi.org/10.7283/HB35-V642, https://doi.org/10.7283/QBZB-Z543, https://doi.org/10.7283/T5M61HHS, https://doi.org/10.7283/61RQ-0887, https://doi.org/10.7283/WSXX-VM46, https://doi.org/10.7283/T5CN725H, https://doi.org/10.7283/GY33-F024, https://doi.org/10.7283/XZAA-W505, https://doi.org/10.7283/T5445JQC, and https://doi.org/10.7283/S8FW-YS19.

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Supplemental Material - 2021jb022990-sup-0001-supporting_information_si-s01.pdf

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Additional details

Created:
October 9, 2023
Modified:
October 24, 2023