Faulting, magmatism and fluid flow during volcanic rifting in East Africa

Dr Ian Bastow (Imperial College London), Dr Snorri Gudbrandsson (Reykjavik Geothermal), Dr Derek Keir, Dr Thomas Gernon
Rationale: 

The breakup of continents is commonly associated with the production of large volumes of molten rock that either intrude the lithosphere or are erupted at the surface. Despite the importance of magmatism during continental breakup, there remains no consensus on how crustal extension is partitioned between magmatic intrusions and mechanical deformation, how magma is stored and transported in the crust prior to erupting at the surface, and how these processes both modulate and are modulated by flow of volatile rich fluids. Recently, the University of Southampton and Imperial College London have operated a number of seismic networks in the Main Ethiopian and Afar rifts of East Africa, which record earthquake activity from fault slip and fluid/magma motion. A core aim of the project will be to record, manage, and analyze local earthquake data from volcanic systems of interest to the geothermal sector (e.g. Tulu Moye, Abaya, Corbetti) to determine the locus and style of earthquake rupture, and whether this brittle failure is linked to subsurface magma, or volatile rich fluid, motions. In addition, depending on the interests of the student, there is the opportunity to conduct field based and remote sensing based studies to map and quantify volcanic systems and active fault networks, and the spatial link to evidence for hydrothermal fluid flow. As such the project aims to link surface and subsurface constraints on faulting, volcanism and fluid flow to better characterize structure and processes in a number of geothermal systems. 

Methodology: 

Seismology - Analysis of earthquake data can be done on both recent, and currently active networks of seismic stations in Ethiopia. The student will map the location, depth extent and geometry of seismically active faults and volcano plumbing systems using modern techniques in earthquake location and relocation. The evolution of earthquake swarms will be determined using cutting edge techniques of waveform cross correlation and frequency analysis. Source mechanisms will also be determined. Newly developed automated techniques for measuring shear(S)-wave splitting will be tested and used to measure seismic anisotropy. Source mechanisms and S-wave splitting will be inverted for the stress state (e.g. Greenfield et al., 2019).

Remote sensing and volcanology - Additional constraints on tectonic and magmatic activity can be acquired from a remote sensing-based analysis of digital elevation models and satellite images of the Ethiopian and Afar rifts. This will primarily entail mapping the fault, fissure and volcanic systems to quantify the surface manifestation of tectonics and magmatism (e.g. Siegburg et al., 2020). Hydrothermal systems will be mapped from remote sensing data using automated spectral classification tools supplemented by field based observations (e.g. Raggiunti et al., 2021). Students interested in a fully multidisciplinary approach can also explore geochemical legacy data and making new major, trace, and isotope measurements to probe the compositional characteristics and tempo of subsurface magmatic processes. 

Location: 
University of Southampton
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered and hosted at the University of Southampton. Specific training will include programming skills in Python and Matlab, and in cutting-edge techniques in earthquake location, shear-wave splitting, and source mechanism inversion. The student will be trained in the field handling and deployment of seismometers, and the management, numerical treatment, and integration of large multidisciplinary datasets. The student will have the opportunity to deploy seismometers, manage new seismic data, and conduct relevant fault analyses, volcanology, and rock sampling fieldtrips in Ethiopia. The student will gain experience in international collaboration (e.g. with Addis Ababa University) and will spend the 3 month-long CASE placement with Reykjavik Geothermal in Iceland. These along with the SOES based thesis-training program will prepare the student for a career path in academia or in industry.

Eligibility & Funding Details: 

Please check https://inspire-dtp.ac.uk/how-apply for details.  

 

Background Reading: 

Greenfield, T., Keir, D., Kendall, J-M., & Ayele, A. (2019). Low-frequency earthquakes beneath Tullu Moye volcano, Ethiopia, reveal fluid pulses from shallow magma chamberEarth and Planetary Science Letters526, 1-11. [115782]. DOI: 10.1016/j.epsl.2019.115782

 

Siegburg, M., Bull, J., Nixon, C., Keir, D., Gernon, T., Corti, G., Ayele, A. (2020). Quantitative constraints on faulting and fault slip-rates in the northern Main Ethiopian RiftTectonics, [e2019TC006046]. DOI: 10.1029/2019TC006046

 

Raggiunti, M., Keir, D., Pagli, C. (2021) Mapping Hydrothermal Alteration at the Fentale-Dofan Magmatic Segment of the Main Ethiopian Rift. Frontiers in Earth Science, doi 10.3389/feart.2021.716144

 

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