Quantifying strain distribution in en-echelon fault systems: Northern Volcanic Zone, NE Iceland
Dr Emma K Bramham (SEE), Dr Douglas Paton (SEE), Dr Estelle Mortimer (SEE)Project partner(s): Dr Asta Rut HjartardottirContact email: E.K.Bramham@leeds.ac.uk
In geological settings that are prone to intense faulting, being able to identify regions of potential future stress accommodation could contribute to forward planning for future hazard mitigation. In magmatically driven rifting environments such as the Mid-Atlantic Ridge, the build-up of stress during lithospheric separation across the plate boundary is released during episodic rifting episodes, with pressurised magma moving to the surface via dyke processes (e.g. Buck et al., 2006, Sigmundsson et al., 2014, Wright et al, 2012). The emplacement of dykes results in the accommodation of stress by both extensional horizontal opening of fractures and vertical slip along the fracture plane (e.g. Tryggvason, 1986, Hjartardottir et al, 2016).
The subaerial environment in Iceland provides an excellent opportunity to measure the surface fractures in a rifting zone to assess the spectrum in behaviour of stress accommodation across both individual fissure swarms and the larger scale volcanic zones. Total horizontal opening measured across selected cross-sections in the northern Krafla fissure swarm has shown that, over the last 10,000 years, Krafla appears to have accommodated the majority of expected horizontal opening in the region (Bramham, 2014). This project will use currently available high resolution LiDAR DEM over the Krafla fissure swarm to further study horizontal extension along the length of the Krafla fissure swarm. The student will also use detailed mapping of fractures across the Northern Volcanic Zone (NVZ) (Hjartardottir et al., 2012, 2015) to plan and acquire high resolution photogrammetry swaths across the fissure swarms to measure horizontal extension across the larger scale and identify regions where there is a stress accommodation deficit.
Additionally the project will study and perform fracture prediction modelling of the smaller scale behaviour of segmented fault systems within the fissure swarms, specifically using fault data extracted from a high resolution DEM over Krafla assessing stress accommodation and identifying regions of deficit.
According to your particular research interests, the studentship could involve:
1. Analysis of the fracture distribution between faults in segmented fault systems using high resolution LiDAR data to identify areas of potential future stress accommodation and using fault displacement data to perform fracture prediction modelling.
2. Quantify horizontal opening across the Krafla fissure swarm. Identification of key areas of potentially low stress accommodation along the fissure swarm.
3. Field work in Iceland to extend high resolution data already available across the Krafla fissure swarm in E-W swaths across the NVZ fissure swarms: to include a combination of drone acquired photogrammetry data, ground truthing and field investigation of key identifiable structures.
4. Quantify total horizontal opening across multiple fissure swarms to assess relative contributions to stress accommodation and identify zone wide deficits.
5. Compare scaled en-echelon fault behaviour - from segmented fault systems to large scale en echelon fissure swarms – to identify regions of future potential stress accommodation.
Bramham, E. K. (2014),LiDAR and InSAR analysis of deformation in the Krafla rift zone, NE Iceland. PhD Thesis, University of Leeds, http://etheses.whiterose.ac.uk/id/eprint/7826
Buck, R.W., Einarsson, P., Brandsdottir, B. (2006) Tectonic stress and magma chamber size as controls on dike propagation: Constraints from the 1975-1984 Krafla rifting episode
Gudmundsson, A., Loetvit, I., (2005) Dyke emplacement in a layered and faulted rift zone, Journal of Volcanology and Geothermal Research, v. 144, p 311-327
Hjartardottir, A.R., Einarsson, P., Bramham, E.K., Wright, T.J.(2012), The Krafla fissure swarm, Iceland, and its formation by rifting events, Bulletin of Volcanology, vol. 74, p 2139-2153.
Hjartardottir, A.R., Einarsson, P., Magnusdottir, S., Bjornsdottir, Þ., Brandsdottir, B. (2015), Fracture systems of the Northern Volcanic Rift Zone, Iceland: an onshore part of the Mid-Atlantic plate boundary, Geological Society Special Publications, v. 420
Hjartardottir, A.R., Einarsson, P., et al., (2016) Fracture movements and graben subsidence during the 2014 Bardarbunga dike intrusion in Iceland, Journal of Volcanology and Geothermal Research, v. 310, p. 242-252
Sigmundsson, F., Hooper, A. et al (2014), Segmented lateral dyke growth in a rifting event at Bárdarbunga volcanic system, Iceland. Nature, vol. 517, p 191-195
Wright, T. J. et al. (2012), Geophysical constraints on the dynamics of spreading centres from rifting episodes on land, Nature Geoscience, v. 5, p. 242-250
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