EGU22-8804, updated on 28 Mar 2022
https://doi.org/10.5194/egusphere-egu22-8804
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Relatively-relocated seismicity during the 2021 Fagradalsfjall dyke intrusion, Reykjanes Peninsula, Iceland: Detailed evolution of a lateral dyke, and comparison to Bárðarbunga-Holuhraun

Esme Olivia Southern1, Tim Greenfield1, Tom Winder1, Þorbjörg Ágústsdóttir2, Bryndís Brandsdóttir3, Tomas Fischer4, Jana Doubravová5, Nick Rawlinson1, Robert White1, Egill Árni Gudnason2, Gylfi Páll Hersir2, Pavla Hrubcova5, and Conor Bacon1
Esme Olivia Southern et al.
  • 1Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
  • 2Iceland GeoSurvey, Reykjavík, Iceland
  • 3Science Institute, Háskóli Íslands, Reykjavík, Iceland
  • 4Faculty of Science, Charles University, Prague, Czech Republic
  • 5Institute of Geophysics, Czech Academy of Sciences, Prague, Czech Republic

The 2021 Fagradalsfjall eruption on Iceland’s Reykjanes Peninsula was preceded by more than 12 months of elevated activity, beginning around November 2019. This dominantly consisted of episodes of intense seismic swarms, but also featured inflationary episodes in both the Svartsengi and Krísuvík volcanic systems. On 24th February 2021, an exceptionally intense episode of seismicity covering the length of the Peninsula marked the initiation of a dyke intrusion, which continued to develop until the 19th of March, when melt first erupted at the surface. The fissure eruption lasted 6 months, ending on 18th September 2021.

During the intrusion, melt first propagated northeast towards Mt Keilir, then to the southwest, eventually forming a 10 km-long dyke. This was marked by more than 80,000 microearthquakes, recorded by a dense local seismic network and detected and located using QuakeMigrate[1].

We present high precision relative relocations of the seismicity, and tightly constrained focal mechanisms of earthquakes which are dominantly located along the base of the dyke. We compare the Fagradalsfjall seismicity to the 2014-2015 Bárðarbunga-Holuhraun intrusion and eruption seismicity [2], in the context of the contrasting tectonic settings, and markedly different precursory activity.

1: Winder, T., Bacon, C., Smith, J., Hudson, T., Greenfield, T. and White, R., 2020. QuakeMigrate: a Modular, Open-Source Python Package for Automatic Earthquake Detection and Location. https://doi.org/10.1002/essoar.10505850.1

2: Woods, J., Winder, T., White, R. S., and Brandsdóttir, B., 2019. Evolution of a lateral dike intrusion revealed by relatively-relocated dike-induced earthquakes: The 2014–15 Bárðarbunga–Holuhraun rifting event, Iceland. https://doi.org/10.1016/j.epsl.2018.10.032

How to cite: Southern, E. O., Greenfield, T., Winder, T., Ágústsdóttir, Þ., Brandsdóttir, B., Fischer, T., Doubravová, J., Rawlinson, N., White, R., Gudnason, E. Á., Hersir, G. P., Hrubcova, P., and Bacon, C.: Relatively-relocated seismicity during the 2021 Fagradalsfjall dyke intrusion, Reykjanes Peninsula, Iceland: Detailed evolution of a lateral dyke, and comparison to Bárðarbunga-Holuhraun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8804, https://doi.org/10.5194/egusphere-egu22-8804, 2022.

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