TY - JOUR

T1 - Cyclical geothermal unrest as a precursor to Iceland’s 2021 Fagradalsfjall eruption

AU - Flóvenz, Ólafur G.

AU - Wang, Rongjiang

AU - Hersir, Gylfi Páll

AU - Dahm, Torsten

AU - Hainzl, Sebastian

AU - Vassileva, Magdalena

AU - Drouin, Vincent

AU - Heimann, Sebastian

AU - Isken, Marius Paul

AU - Gudnason, Egill

AU - Ágústsson, Kristján

AU - Ágústsdóttir, Thorbjörg

AU - Horálek, Josef

AU - Motagh, Mahdi

AU - Walter, Thomas R.

AU - Rivalta, Eleonora

AU - Jousset, Philippe

AU - Krawczyk, Charlotte M.

AU - Milkereit, Claus

N1 - Funding Information: The authors are grateful to all those who assisted to generate this article, including H. Geirsson, University of Iceland, for providing the time series of a permanent GNSS station, allowing us to control InSAR data; I. Þór Magnússon for collecting and processing the gravity data; Þ. Þórðarson, University of Iceland, and A. Hobé, Uppsala University, for useful discussions; E. Bali and G. H. Guðfinnsson, University of Iceland, for valuable assistance with the geochemical calculations; Mila Telecommunication Company for access to the fibre-optic cable; Iceland Met Office for the access to the earthquake catalogue, seismic waveforms and GNSS stations; and C. Wollin, K. Erbas and T. Reinsch for DAS assistance. The fieldwork of GFZ was part of a HART rapid response activity funded by GFZ. DEM(s) were created from DigitalGlobe, Inc., imagery and funded under National Science Foundation awards 1043681, 1559691 and 1542736. The work of M.P.I. was supported by the DEEPEN project (BMWI 03EE4018).

PY - 2022/5

Y1 - 2022/5

N2 - Understanding and constraining the source of geodetic deformation in volcanic areas is an important component of hazard assessment. Here, we analyse deformation and seismicity for one year before the March 2021 Fagradalsfjall eruption in Iceland. We generate a high-resolution catalogue of 39,500 earthquakes using optical cable recordings and develop a poroelastic model to describe three pre-eruptional uplift and subsidence cycles at the Svartsengi geothermal field, 8 km west of the eruption site. We find the observed deformation is best explained by cyclic intrusions into a permeable aquifer by a fluid injected at 4 km depth below the geothermal field, with a total volume of 0.11 ± 0.05 km3 and a density of 850 ± 350 kg m–3. We therefore suggest that ingression of magmatic CO2 can explain the geodetic, gravity and seismic data, although some contribution of magma cannot be excluded.

AB - Understanding and constraining the source of geodetic deformation in volcanic areas is an important component of hazard assessment. Here, we analyse deformation and seismicity for one year before the March 2021 Fagradalsfjall eruption in Iceland. We generate a high-resolution catalogue of 39,500 earthquakes using optical cable recordings and develop a poroelastic model to describe three pre-eruptional uplift and subsidence cycles at the Svartsengi geothermal field, 8 km west of the eruption site. We find the observed deformation is best explained by cyclic intrusions into a permeable aquifer by a fluid injected at 4 km depth below the geothermal field, with a total volume of 0.11 ± 0.05 km3 and a density of 850 ± 350 kg m–3. We therefore suggest that ingression of magmatic CO2 can explain the geodetic, gravity and seismic data, although some contribution of magma cannot be excluded.

UR - http://www.scopus.com/inward/record.url?scp=85129252410&partnerID=8YFLogxK

U2 - 10.21203/rs.3.rs-636186/v1

DO - 10.21203/rs.3.rs-636186/v1

M3 - Article

AN - SCOPUS:85129252410

VL - 15

SP - 397

EP - 404

JO - Nature geoscience

JF - Nature geoscience

SN - 1752-0894

IS - 5

ER -