Stress variations and non-shear earthquakes before the 2021 Iceland eruption trace magmatic fluid flow
Abstract The 2021 Fagradalsfjall eruption on Iceland’s Reykjanes Peninsula was preceded by an intense seismic swarm, offering an opportunity to investigate fluid dynamics and faulting processes at divergent plate boundary. Here we analysed 1306 full moment tensors of pre-eruption dike-related earthq...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-07-01
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| Series: | Communications Earth & Environment |
| Online Access: | https://doi.org/10.1038/s43247-025-02533-5 |
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| Summary: | Abstract The 2021 Fagradalsfjall eruption on Iceland’s Reykjanes Peninsula was preceded by an intense seismic swarm, offering an opportunity to investigate fluid dynamics and faulting processes at divergent plate boundary. Here we analysed 1306 full moment tensors of pre-eruption dike-related earthquakes and identified three faulting regimes: strike-slip, normal and reverse, driven by variations in vertical stress and controlled by fluid dynamics and crustal heterogeneity. Systematic volumetric components of these earthquakes revealed both tensile opening and compressive closing of cracks. Notably, crack closing dominated shallow, fractured crust, associated with surface subsidence above the dike, while crack opening occurred within the impermeable crust, suggesting overpressured fluids trapped at structural barriers. These variations highlight the role of fluid-rock interactions and anisotropic permeability in driving fault behaviour. Our results demonstrate that non-double-couple components of earthquakes are sensitive indicators of evolving stress and fluid migration. They provide insights into the mechanics of seismo-volcanic unrest at the slow-spreading rift. |
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| ISSN: | 2662-4435 |