IAP-24-124

Passive Seismic Imaging of Under-explored Central Iceland

Iceland is one of the most seismically and volcanically active countries on Earth, driven by complex tectonics of a spreading plate tectonic boundary interacting with an underlying mantle hotspot. A dense permanent monitoring network covers much of southern and northern Iceland, and numerous small-scale temporary networks have targeted specific volcanoes and rift systems shedding light on local melt migration processes. Until now, vast areas of central Iceland were sparsely instrumented and are accordingly understudied (Fig. 1a). This project will analyse data from a new network of 15 broadband seismometers that were deployed in the remote highlands of central Iceland in summer 2024 .

The field site contains three active volcanoes covered by two major ice sheets, which supply magma to the surrounding magmatic rifts, and heat to four high-temperature geothermal systems . This little-studied section of the Icelandic plate-tectonic boundary is tectonically significant, bridging the Northern/Eastern, Central and Western Volcanic Zones (VZ), which delineate the northern boundary of the hypothesised “Hreppar” microplate, Fig 1a . The region is likely to represent a significant change in crustal formation processes across the 3 volcanic rift zones, which are in different stages of their life-cycle, and experience varying levels of interaction with the underlying mantle hotspot which is thought to be centred to the east of the study region.
The candidate will assist in the field maintenance of the network and analysis of seismic data collected by it, using passive seismic methods to address one or more of the following scientific objectives depending on their interests:
• Explore the lateral extent of hotspot influence on crustal formation across Iceland: Changes in crustal thickness and structure will be assessed to explore how crustal formation changes with varying levels of hotspot interaction.
• Test the existence of the Hreppar microplate : Investigate crustal fracture orientations using measurements of seismic anisotropy from local earthquakes to assess changing local tectonics across rift systems
• Image upper mantle flow patterns to determine how plume material spreads in the upper mantle: Using measurements of seismic anisotropy from distant global earthquakes

Numerous methods can be used to explore crustal thickness and seismic velocity structure, but these are rarely directly compared for consistency or used in combination. This work will use data from recordings of both distant global (teleseismic) earthquakes that produce converted and reflected seismic waves that interact with the crust-mantle interface (Moho), and ambient seismic noise generated by the surrounding oceans. Techniques that may be explored include:
• Analysis of P to s converted waves using receiver function analysis and joint inversion with surface wave dispersion (Jenkins et al., 2018)
• Analysis of reflected waves using Vertical Deep Seismic Sounding (Linang et al., 2022)
• Global phase Interferometry (Bianchi et al., 2021 et al.)
• Ambient noise Auto correlation (Taylor et al., 2016)
The student will compare results of these different methods to explore consistency between techniques and work to develop new approaches that combine them in a joint inversion.
Exploration of crustal seismic anisotropy will be assessed through shear wave splitting observed in local seismicity (Bacon et al., 2022). Upper mantle flow will be explored via splitting of shear waves from distant global earthquakes in core traversing SKS, SKKS and PKS phases (e.g. Bjarnason et al., 2002)

Year 1

Collection of 1st year of seismic data in field trip summer 2025 (likely late July prior to official PhD start). Assistance with data archiving and formatting. Literature review of area/crustal imaging methods. Learning and applying crustal imaging techniques to data, comparing initial results, and developing an approach to combine methods.

Year 2

2nd year data collection, field trip summer 2026. Assistance with data archiving and formatting. Inclusion of new data to imaging work, to produce final dataset. Paper on combined data method, paper on application to central Iceland and implications of observations for crustal formation processes.

Year 3

Analysis of crustal and/or mantle anisotropy. Paper/s on results.

Year 3.5

Paper and thesis writing

You will become part of the Geophysics and Geodynamics Research Group at Durham.
The student will receive training in seismic field work and instrumentation as well as processing, analysing and modelling seismic data, and other essential skills (programming, code development). Training in a wider range of important skills (e.g. presentation, paper/thesis writing) will be provided by the Department of Earth Sciences at Durham University.
The student will have opportunities to work with other partners in the UK (University East Anglia, Birkbeck, Aberdeen, Cambridge) and internationally (Iceland) and will attend national and international scientific meetings to present results. We aim to see all students publish at least two papers in leading scientific journals during their PhD. Upon completion, the student will be well equipped for a career in academia or in a range of industries