Deep long period seismicity preceding and during the 2021 Fagradalsfjall eruption, Iceland

0572684 - GFÚ 2024 RIV DE eng J - Journal Article
Greenfield, T. - Winder, T. - Rawlinson, N. - Maclennan, J. - White, R. S. - Ágústsdóttir, T. - Bacon, C. A. - Brandsdóttir, B. - Eibl, E.P.S. - Glastonbury-Southern, E. - Gudnason, E. Á. - Hersir, G. P. - Horálek, Josef
Deep long period seismicity preceding and during the 2021 Fagradalsfjall eruption, Iceland.
Bulletin of Volcanology. Roč. 84, č. 12 (2022), č. článku 101. ISSN 0258-8900. E-ISSN 1432-0819
R&D Projects: GA TA ČR(CZ) TO01000198
Institutional support: RVO:67985530
Keywords : deep long-period earthqukes * magma plumbing system * Iceland * Reykjanes * Fagradalsfjall * low frequency
OECD category: Volcanology
Impact factor: 3.5, year: 2022
Method of publishing: Open access
https://link.springer.com/article/10.1007/s00445-022-01603-2

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.
Permanent Link: https://hdl.handle.net/11104/0343293