TY  - JOUR
A1  - Greenfield, Tim
A1  - Winder, Tom
A1  - Rawlinson, Nicholas
A1  - Maclennan, John
A1  - White, Robert S.
A1  - Ágústsdóttir, Thorbjörg
A1  - Bacon, Conor Andrew
A1  - Brandsdóttir, Bryndis
A1  - Eibl, Eva P. S.
A1  - Glastonbury-Southern, Esme
A1  - Gudnason, Egill Árni
A1  - Hersir, Gylfi Páll
A1  - Horálek, Josef
T1  - Deep long period seismicity preceding and during the 2021 Fagradalsfjall eruption, Iceland
JF  - Bulletin of volcanology : official journal of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI)
N2  - We use a dense seismic network on the Reykjanes Peninsula, Iceland, to image a group of earthquakes at 10-12 km depth, 2 km north-east of 2021 Fagradalsfjall eruption site. These deep earthquakes have a lower frequency content compared to earthquakes located in the upper, brittle crust and are similar to deep long period (DLP) seismicity observed at other volcanoes in Iceland and around the world. We observed several swarms of DLP earthquakes between the start of the study period (June 2020) and the initiation of the 3-week-long dyke intrusion that preceded the eruption in March 2021. During the eruption, DLP earthquake swarms returned 1 km SW of their original location during periods when the discharge rate or fountaining style of the eruption changed. The DLP seismicity is therefore likely to be linked to the magma plumbing system beneath Fagradalsfjall. However, the DLP seismicity occurred similar to 5 km shallower than where petrological modelling places the near-Moho magma storage region in which the Fagradalsfjall lava was stored. We suggest that the DLP seismicity was triggered by the exsolution of CO2-rich fluids or the movement of magma at a barrier to the transport of melt in the lower crust. Increased flux through the magma plumbing system during the eruption likely adds to the complexity of the melt migration process, thus causing further DLP seismicity, despite a contemporaneous magma channel to the surface.
KW  - deep long-period earthquakes
KW  - magma plumbing system
KW  - Iceland
KW  - Reykjanes
KW  - low-frequency
KW  - Fagradalsfjall
Y1  - 2022
U6  - https://doi.org/10.1007/s00445-022-01603-2
SN  - 0258-8900
SN  - 1432-0819
VL  - 84
IS  - 12
PB  - Springer
CY  - Berlin ; Heidelberg ; New York
ER  - 
TY  - JOUR
A1  - Flóvenz, Ólafur G.
A1  - Wang, Rongjiang
A1  - Hersir, Gylfi Páll
A1  - Dahm, Torsten
A1  - Hainzl, Sebastian
A1  - Vassileva, Magdalena
A1  - Drouin, Vincent
A1  - Heimann, Sebastian
A1  - Isken, Marius Paul
A1  - Gudnason, Egill Á.
A1  - Ágústsson, Kristján
A1  - Ágústsdóttir, Thorbjörg
A1  - Horálek, Josef
A1  - Motagh, Mahdi
A1  - Walter, Thomas R.
A1  - Rivalta, Eleonora
A1  - Jousset, Philippe
A1  - Krawczyk, Charlotte M.
A1  - Milkereit, Claus
T1  - Cyclical geothermal unrest as a precursor to Iceland's 2021 Fagradalsfjall eruption
JF  - Nature geoscience
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.
Y1  - 2022
U6  - https://doi.org/10.1038/s41561-022-00930-5
SN  - 1752-0894
SN  - 1752-0908
VL  - 15
IS  - 5
SP  - 397
EP  - 404
PB  - Nature Research
CY  - Berlin
ER  -