Post‐Rifting Relaxation During 2015–2020 Following the Bárðarbunga‐Holuhraun Dike Intrusion and Eruption in Iceland

Abstract

Post‐rifting ground deformation may be driven by viscoelastic relaxation of stresses generated by dike intrusions. The single‐dike intrusion of the 2014–2015 Bárðarbunga eruption in Iceland presents an opportunity for a detailed study of this process. We use continuous Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) velocity fields to analyze the 2015–2020 post‐rifting deformation, showing uplift on both sides of the dike and horizontal displacement away from the dike after correcting for background deformation. Two GNSS stations experience baseline lengthening at a rate of 19 mm/yr in the direction perpendicular to the strike of the dike. A two‐layer viscoelastic model with a 0.4 × 1019 Pa s viscoelastic half‐space overlain by an 18 km thick elastic layer best explains the observed horizontal and vertical InSAR and GNSS displacements. The model misfit space shows a second regime of good fit, likely driven by deformation near the dike that may result from cooling compaction of the emplaced dike.

On the Move: 2023 Observations on Real Time Graben Formation, Grindavík, Iceland

“…Importantly, small grabens (<100 m to <1 km wide and generally symmetric) are supported by modeling and field mapping (e.g., Mastin & Pollard, 1988) and attributed to magma intrusions, in addition to major grabens (>3 km wide) associated with plate boundary extensional tectonics (e.g., Afar in 1978, Abdallah et al., 1979; this study; Supporting Information ), or to magma intrusions (e.g., S. Jónsson, 2012). Some intrusions may lead to eruptions (e.g., Iceland's 2014‐15 Holuhraun event; Li et al., 2022), while others terminate in blind intrusions (e.g., Akutan, Alaska in 1996, Lu et al., 2000, or Harrat Lunayyir, Saudi Arabia in 2009, Pallister et al., 2010). The Akutan event had ∼3,000 earthquakes (up to Mmax 5.1) and produced extensive ground cracks (Lu et al., 2000) with both vertical and horizontal deformation attributed to either extensional tectonics or a magma intrusion, but no clear graben.…”

“…InSAR (Xu et al., 2016) and drone mapping (Trippanera et al., 2019) attributed deformation in Saudi Arabia to dike induced faulting with a 10‐km‐long, 1‐m‐deep, and up to 5 km‐wide graben (S. Jónsson, 2012). The 2014‐15 Holuhraun graben is 700–1,000 m wide, symmetric, and up to 5 m deep and clearly associated with an eruption that partially covered portions of the graben with lava (Hjartardóttir et al., 2016; Li et al., 2022). In Grindavík, the system of two grabens and a central horst are up to 4.5 km wide at the surface or generally several times wider than these aforementioned studies (Supporting Information ), where the grabens are largely attributed to dike injections.…”