Pre-existing structures control the orientation of strike-slip faulting during the 2021 dike intrusion at Fagradalsfjall, Iceland
Year: 2025
Type: article
Abstract: The 2021 Fagradalsfjall inflation and dike intrusion marked the initiation of a new era of volcanism on Iceland’s Reykjanes Peninsula. We present a large automatic catalog consisting of more than 80,000 earthquake hypocenters spanning the full period of the dike intrusion, which were derived from seismic data recorded by a dense network of seismometers. The 9 – 10 km long dike exhibits a two-segment geometry of similar lengths. Linear regression on a relatively relocated subset of over 12,000 earthquakes revealed a strike of 029° with a standard deviation of 2° in the southern segment, and 046° with a standard deviation of 1° in the northern segment of the dike. A total of 97 detailed fault plane solutions from selected subsets of events provide new insight into the controls on faulting, showing almost exclusively right-lateral strike slip/oblique-slip faulting associated with the dike intrusion, and a lack of left-lateral strike-slip fault motion. The alignment of fault planes is consistent with the orientation of pre-existing structures, within uncertainty estimates. In light of these observations, we conclude that the dominant controlling factor on the orientation of dike-related faulting is the extensive network of pre-existing structures formed by the active transtensional plate boundary along the Reykjanes Peninsula.
Source: Apollo (University of Cambridge)
DOI: 10.17863/cam.118896
Authors: Southern, Esme, Winder, Tom, Rawlinson, Nicholas, White, Robert S, Greenfield, Tim, Bacon, Conor Andrew, Ágústsdóttir, Thorbjörg, Brandsdóttir, Bryndís, Gudnason, Egill Árni, Hersir, Gylfi Pall, Fischer, Tomas J, Doubravová, Jana, Hrubcová, Pavla, Eibl, Eva PS
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6925576449
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