skip to content

Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Sergei Lebedev, Earth Sciences

Co-Supervisor: Nick Rawlinson, Earth Sciences

Brief summary: 
The rapid recent growth in the amount of seismic data presents an opportunity for unprecedentedly detailed imaging of tectonic and volcanic processes globally, using seismic waveform tomography.
Importance of the area of research concerned: 
Within the Earth’s tectonic plates, the lithosphere shows great lateral variability in its age, evolution, chemical composition, thickness and mechanical strength. Beneath the lithosphere, hot viscous mantle convects in enigmatic currents at a broad range of scales. The dynamic processes in the lithosphere and the mantle beneath it give rise to mountain building, earthquakes and volcanoes and shape the continuing evolution of the Earth’s surface and its interior. Global seismic tomography uses millions of seismograms recorded worldwide, solves very large inverse problems, and produces 3D models of the distribution of seismic velocities within the Earth. Seismic velocities and their directional dependence (anisotropy) give us unique evidence on the physical structure and deformation of the lithosphere and underlying mantle. The tomographic model created in this project will give us new insights into how the Earth works. It is likely to be used as reference by Earth scientists around the world for many years to come.
Project summary : 
The explosive recent growth in the amount of the seismic data has created a much denser sampling of the Earth than available only recently. The goal of this project is to use all the data available globally to build a new seismic-velocity model of the Earth’s crust and upper mantle, with resolution higher than that of the previous generations of models. Most of the seismic waveform data has already been assembled in the project supervisor’s group. After completing this dataset with the most recent data, which will be retrieved from international data centres, the student will build the new model. Numerically efficient, well tested waveform tomography methods are already available, but there will also be opportunities for further method development. The new model is likely to prompt exciting discoveries on the deep mechanisms of tectonics and magmatism.
What will the student do?: 
The student will work with a very large dataset of millions of seismic waveforms. The existing dataset will be completed with the most recent data. Then, fully automated pre-processing, quality control and waveform inversions will be performed, paving the way for the calculation of the global, 3D tomographic model. Fine-tuning the new model will increase its resolution and accuracy. New approaches may be developed for the suppression of the effects of data errors and for optimising the regularisation of the inversion. Once the model is computed, it will be interpreted and analysed quantitatively together with other relevant geophysical and geological data. This is likely to prompt more learning and expanding one’s perspective and is usually an exciting, rewarding process, with new discoveries always waiting to be made.
References - references should provide further reading about the project: 
Celli, N.L., S. Lebedev, A.J. Schaeffer, C. Gaina, 2020. African cratonic lithosphere carved by mantle plumes. Nature Communications, 11, 92, doi:10.1038/s41467-019-13871-2.
Lebedev, S., A. J. Schaeffer, J. Fullea, V. Pease, 2018. Seismic tomography of the Arctic region: Inferences for the thermal structure and evolution of the lithosphere. In Pease, V. & Coakley, B. (eds.) Circum-Arctic Lithosphere Evolution. Geological Society, London, Special Publications, 460, 419-440, https://doi.org/10.1144/SP460.10.
Schaeffer, A. J. & S. Lebedev, 2013. Global shear-speed structure of the upper mantle and transition zone. Geophys. J. Int., 194, 417–449.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Sergei Lebedev
Prof Nicholas Rawlinson
Department of Earth Sciences Graduate Administrator